On the apple tree, the infections occur on leaves, fruit and young twigs. The brightly colored spots produced on the leaves make it easy to identify. Small, pale yellow spots appear on the upper surfaces of the leaves, usually during late April or May on the eastern seaboard of the United States. These spots gradually enlarge and turn orange or red and may show concentric rings of color. Drops of orange liquid may be visible on the spots. Later in the season, black dots appear on the orange spots on the upper leaf surface. In late summer, tube-like structures develop on the undersurface of the apple leaf. Infected leaves sometimes drop prematurely, particularly during drought conditions or when the tree is under additional stress. Infections on fruit are usually near the blossom end and are somewhat similar to the leaf lesions. On the eastern red cedar host, the fungus produces reddish-brown galls from 1⁄4–1 inch (6.4–25.4 mm) in diameter. These galls can be mistaken for cone structures by the uninitiated. After reaching a diameter of about 1⁄2 inch (13 mm), they show many small circular depressions. In the center of each depression is a small, pimple-like structure. In the spring these structures elongate into orange gelatinous protrusions or horns. The spore-bearing horns swell during rainy periods in April and May. The wind carries the microscopic spores to infect apple leaves, fruit and young twigs on trees within a radius of several miles of the infected tree. On other species of juniper more common in landscaping and bonsai, the sizes of the infections are reduced. Early in the infection, the galls are small bumps on the woody portions of the plant. They maintain the orange gelatinous form after the first warm rains of spring but generally on a greatly reduced scale.

Signs of damage

Fungicide sprays applied in a timely manner are highly effective against the rust diseases during the apple cycle. Most sprays are applied four times at 7- to 10-day intervals, starting with pink bud on crabapples. These applications are to protect the apples from spores being released from the cedar host in mid-spring. If cedar apple rust disease is diagnosed on apple fruits and leaves it is far too late to spray. Systemic fungicides are available. Fungicides listed for use on apples can be used in July and August on the cedars to reduce infection. Application of fungicides to the junipers before and while they are in the infectious orange gelatinous state seems to reduce the severity of the outbreak.

How to prevent

Because apples are an economically important crop, control is usually focused there. Interruption of the disease cycle is the only effective method for control of the cedar apple rust. The recommended method of control is to “remove cedars located within a 1 mile (1.6 km) radius” of the apples to interrupt the disease cycle, though this method is seldom practical. For those doing bonsai, it is common to have the trees within feet of each other and on the central eastern seaboard of the United States, Eastern Red Cedar is a common first-growth conifer along roadsides.

Treat

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Cedar-apple rust

Ascomycetes are characterized by septate hyphae with simple pores. Asexual reproduction by conidia. Sexual reproduction by ascospores, typically eight, in an ascus. Asci are often housed in a fruiting body or ascocarp e.g. cleistothecia or perithecia.

Good gardening habits and effective treatment help prevent, stop and control fungal disease: 

1. Start by planting healthy stock. ...
2. Choose planting sites based on plant needs. ...
3. Avoid overhead watering. ...
4. Water early in the day. ...
5. Don't crowd plants. ...
6. Don't work a wet garden. ...
7. Treat with a trusted, proven fungicide.

To control fungal outbreaks, as with bacteria, remove all infected plant parts, or plants. You may also choose to apply a fungicide. There are many products available for treatment, organically (copper, sulfur, and baking soda are common) or synthetically.

Ascomycetes

The term “abiotic disorders” refers to a wide array of plant problems. We use the word “abiotic” to indicate that the symptom is not caused by a biological agent such as an insect, mite or pathogen.

Examine where symptoms first appear on a plant—on new leaves, old leaves or all over? Note the pattern of any discolouration or yellowing—is it all over, between the veins or around the edges? If only the veins are yellow, deficiency is probably not involved. Note general patterns rather than looking at Individual plants—are the symptoms distributed throughout a group of plants of the same type growing together? In the case of a deficiency all of the plants should be similarly effected, although distribution will depend on past treatments applied to the soil. Soil analysis, such as determining pH, can help to confirm the presence of physiological disorders. Considering recent conditions, such as heavy rains, dry spells, frosts, etc., may also help to determine the cause of plant disorders.

Testing soil and fertilizing accordingly. Collecting and testing samples to identify and treat pests or diseases. Aerating compacted soil with an air tool to “fluff” it without damaging roots. Pruning to help a tree recover from damage caused by storms, road salt, or extreme temperatures.

Abiotic

Symptoms of Phytophthora diseases are not restricted to root rots because some species attack only aboveground parts of the plant. Large necrotic leaf or stem blotches characterize late blight of potato and tomato. Under the leaf, along the leading edge of the necrotic tissue, a downy, white growth may develop. Defoliation and a dieback starting at branch tips characterize holly tip blight. Rhododendrons develop a leaf spot and blight in winter caused by P. syringae. Crabapple or flowering pear nursery stock can develop a black, sunken canker several inches above the soil due to the same organism.

The most effective way of preventing Phytophthora rot diseases is to provide good drainage and to practice good water management. Along with the appropriate cultural controls, the fungicide fosetyl-al (Aliette) may be used on a number of ornamental plant species to help prevent Phytophthora infections.

High temperatures have been used to control Phytophthora in many ways. Steam heat is effective to kill Phytophthora in contaminated soil, media or on planting containers such as pots. If you re-use pots you can soak pre-cleaned pots in hot (180°F) water for at least 30 min or use aerated steam (140°F) for 30 min.

Phytophthora

Plants infected by chrysanthemum white rust exhibit spots on the upper surfaces of leaves. These spots are initially pale-green to yellow in color and up to 5mm in diameter, but may turn brown as the tissue becomes necrotic. On the underside of the leaf, the spots develop into pink or white pustules that become prominent as the teliospores develop.

Buy cuttings from a reliable source. Inspect them when they come in and regularly thereafter for symptoms of white rust. Water with drip tapes or individual emitters if possible to avoid splashing spread via overhead irrigation.

Keep susceptible cultivars isolated. Pick off and burn affected leaves. Use cuttings from healthy plants only. Remove plant debris and escaped plants. Keep humidity low, and avoid wetting foliage.

Chrysanthemum white rust

Most of the time, this pest is identified by the leaf miner damage. Frequently, it appears as yellow, squiggly lines in the leaves. This is where the leaf miner larva have literally bored their way through the leaf. Leaf miner damage can also appear as spots or blotches.

Pick off and destroy badly infested leaves in small gardens. The more healthy the plant, the less chance that leafminers will hurt it. Maintain plant health with organic fertilizers and proper watering to allow plants to outgrow and tolerate pest damage. Keep your soil alive by using compost and other soil amendments.

The most common method to rid plants of leaf miners is to spray general pesticide on the infected plants. The trick to this method of how to kill leaf miners is to spray at right time. If you spray too early or too late, the pesticide will not reach the leaf miner larva and will not kill the leaf miner flies.

Leaf miners

Tissues affected by the symptoms of Erwinia amylovora include blossoms, fruits, shoots, and branches of apple (Pomoideae), pear, and many other rosaceous plants. All symptoms are above ground and are typically easy to recognize. Symptoms on blossoms include water soaking of the floral receptacle, ovary, and peduncles. This results in a dull, gray-green appearance at 1–2 weeks after petal fall, and eventually tissues will shrivel and turn black. The base of the blossom and young fruit show similar symptoms as infection spreads. Opaque white- or amber-colored droplets of bacterial ooze can be seen on the infected tissue when the environment is high in humidity. Shoots show similar symptoms but develop much more rapidly. A “Shepherd's Crook” can be seen when the tip of the shoot wilts, and diseased shoot leaves typically have blackening along the mid-vein and then die. In number, diseased shoots give the tree a blighted appearance. Initial infection of blossoms and shoots can spread to larger tree limbs. Branches will darken and become water soaked. Advanced infection develops cracks in bark and a sunken surface. Wood under the bark will become streaked with black discoloration. Immature fruit forms water-soaked lesions and later turned black. Bacterial ooze can be found on these lesions. Severe infections result in fruit turning entirely black and shriveling.

Phytosanitary measures have been employed as the best sanitary measures against E. amylovora dispersal. High risk countries are encouraged not to import plants susceptible to the pathogen into their territory because, once the bacteria become established in an area it is nearly impossible to eradicate the disease. Nurseries and orchards in such regions are placed on strict phytosanitary surveillance measures and well-monitored. Imported and infected crops are destroyed as soon as they are noticed since the bacteria spreads very rapidly and eradication methods are usually costly and inefficient.

The only effective treatment for plants already infected is to prune off the affected branches and remove them from the area. Plants or trees should be inspected routinely for the appearance of new infections. The rest of the plant can be saved if the blighted wood is removed before the infection spreads to the roots. There is no known cure; prevention is the key.

Fire blight

Initial symptoms include large, angular or blocky, yellow areas visible on the upper surface. As lesions mature, they expand rapidly and turn brown. The under surface of infected leaves appears watersoaked. Upon closer inspection, a purple-brown mold (see arrow) becomes apparent. Small spores shaped like footballs can be observed among the mold with a 10x hand lens. In disease-favorable conditions (cool nights with long dew periods), downy mildew will spread rapidly, destroying leaf tissue without affecting stems or petioles.

As downy mildew like moist conditions, avoid dense planting and control weeds, to provide good air circulation around the plants. Water plants early in the morning, like watering plants in the evening, leads to high humidity that persists throughout the night.

Because the downy mildew pathogen does not overwinter in midwestern fields, crop rotations and tillage practices do not affect disease development. The pathogen tends to become established in late summer. Therefore, planting early season varieties may further reduce the already minor threat posed by downy mildew. Fungicides applied specifically for downy mildew control may be unnecessary. Broad spectrum protectant fungicides such as chlorothalonil, mancozeb, and fixed copper are at least somewhat effective in protecting against downy mildew infection. Systemic fungicides are labeled for use against cucurbit downy mildew, but are recommended only after diagnosis of this disease has been confirmed. One way to control downy mildew is to eliminate moisture and humidity around the impacted plants. Watering from below, such as with a drip system, and improve air circulation through selective pruning. In enclosed environments, like in the house or in a greenhouse, reducing the humidity will help as well.

Downy mildew

Typical symptoms of potassium deficiency in plants include brown scorching and curling of leaf tips as well as chlorosis (yellowing) between leaf veins. Purple spots may also appear on the leaf undersides. Plant growth, root development, and seed and fruit development are usually reduced in potassium-deficient plants. Often, potassium deficiency symptoms first appear on older (lower) leaves because potassium is a mobile nutrient, meaning that a plant can allocate potassium to younger leaves when it is K deficient. Deficient plants may be more prone to frost damage and disease, and their symptoms can often be confused with wind scorch or drought. The deficiency is most common in several important fruit and vegetable crops; notably potatoes, brassicas, tomatoes, apples, currants, gooseberries, and raspberries. Sugar beets, cereals, and clover are also commonly affected.

The best way to prevent or solve this deficiency, is to add a potassium fertilizer to the plant. If necessary, it can be added to the nutritional feeding schedule if the shortage keeps occurring.

The most widely used potassium fertilizer is potassium chloride (muriate of potash). Other inorganic potassium fertilizers include potassium nitrate, potassium sulfate, and monopotassium phosphate. Potassium-rich treatments suitable for organic farming include feeding with home-made comfrey liquid, adding seaweed meal, vermiculite, composted bracken, and compost rich in decayed banana peels. Wood ash also has high potassium content but must be used cautiously due its effect on pH level. Adequate moisture is necessary for effective potassium uptake; low soil water reduces K uptake by plant roots. Liming acidic soils can increase potassium retention in some soils by reducing leaching; practices that increase soil organic matter can also increase potassium retention.

Potassium deficiency

Spider mites damage foliage by sucking juices from the leaves. This shows up as stippling on the leaves and more severe damage can result in leaf bronzing that may lead to leaf drop. Leaf drop increases incidence of sun/light burn and negatively affects both vegetative and flowering stages. 
Additional signs of spider mites are curled and/or burned leaf edges as well as leaves that have taken on a leathery texture. Webbing will be produced when mite populations grow in size and can be found on foliage, twigs and fruit/buds.

Look before you buy:
Inspect indoor and outdoor plants before purchasing to make sure they aren’t infested.
Keep plants healthy:
Make sure plants are well-watered and fertilized. Healthy plants are more able to withstand pests and diseases, while weakened or stressed plants are more susceptible to problems.
Keep the area clean:
Clear weeds and debris out of garden areas where pests can more easily hide.
Bump up moisture levels:
Since spider mites thrive in dry conditions, keep air humidity levels higher around plants.
Use high-quality soil:
Use a high-quality, sterile potting soil to avoid possible soil-borne pests.

Chemical pesticide use actually encourages the spread of spider mites by killing the beneficial insects that prey on them. Mites are also known to develop quick resistance to various pesticides. For these reasons, it’s important to control mites with effective natural and organic methods.
1 Prune leaves, stems and other infested parts of plants well past any webbing and discard in trash (and not in compost piles). Don’t be hesitant to pull entire plants to prevent the mites spreading to its neighbors.
2 Wash plants with a strong stream of water and reduce pest numbers.
3 Commercially available beneficial insects, such as ladybugs, lacewing and predatory mites are important natural enemies. For best results, make releases when pest levels are low to medium.
4 Nuke Em, a relatively new organic insecticide containing food-grade ingredients, works fast and kills most indoor gardening pests at the egg, larvae or adult stage. Best of all, it does this without leaving a residue on the leaves that can impact flavor.
5 BotaniGard ES is a highly effective biological insecticide containing Beauveria bassiana, an entomopathogenic fungus that attacks a long-list of troublesome crop pests – even resistant strains! Weekly applications can prevent insect population explosions and provide protection equal to or better than conventional chemical pesticides.
6 Mix Pure Neem Oil with Coco-Wet and apply every 3-5 days to kill pest eggs indoors and interrupt the reproductive cycle. Make sure to spray all plant parts, including the undersides of leaves. Do NOT apply when temperatures exceed 90˚F and wait at last six hours before turning lights on.
7 If populations are high, use a least-toxic, short-lived pesticide (Take Down Spray, Doktor Doom Foggers) to reduce infestations, then release predatory mites to maintain control.
8 Insecticidal soap or botanical insecticides can be used to spot treat heavily infested areas.
9 On fruit trees, horticultural oil should be applied early in the season or late in the fall to destroy overwintering eggs.
10 Dust on leaves, branches and fruit encourages mites. A mid-season hosing (or two!) to remove dust from trees is a worthwhile preventative.
11 Water stress makes both trees and garden plants more susceptible to mite infestations. Make sure your plants are properly watered.

Spider Mites

Wilting, stunting, uneven plant growth, crown rot, plant death. Roots are discolored, the cortex may slough off, leaving the vascular cylinder.

Fertilize carefully with a slow-release formula in summer months. Water long and sparingly (no more than once a week), early in the day. This way, grass blades have a chance to dry out before nightfall. Aerate the soil to prevent thatch buildup and to loosen compacted, poorly draining soil.

For warm-season Pythium diseases, time fungicide applications preventively or at the very first onset of disease symptoms.

Pythium diseases

If your plant is not getting enough light, the most common sign is the yellowing and dropping of leaves, stunted leaf growth, elongated stems, and a dull-green color. If your plant is getting too much light, then its leaves will have singed tips, burned patches, or will be falling off (yikes!).

You can prevent this from happening by turning the plant once a week or every time you water. This ensure all leaves are exposed to roughly the same amount of light. All plants will bend towards their light source, and we recommend turning all your houseplants at least once a week to prevent “one-sided” growth.

Most plants will survive illuminance ten times lower than listed below but will not grow as well or bloom. Most plants grown as houseplants are selected because they are already adapted to growing at typical house temperatures, between 15° and 25°C. Exceptions do occur, and some plants require chilling periods at lower temperatures (down to 5° or 10°) in winter when less light is available. Houseplants are generally grown in specialized soils called potting compost or potting soil, not in local natural soil. A good potting compost mixture includes soil conditioners to provide the plant with nutrients, support, adequate drainage, and proper aeration. Most potting composts contain a combination of peat and vermiculite or perlite. Concern over environmental damage to peat bogs, however, is leading to the replacement of peat by coir (coconut fibre), which is a sustainable resource. Sterilised soil can also be used.

Lack of light

Raised yellowish-orange, powdery pustules on the surface of infected foliage. Significant foliar dieback occurs on especially susceptible cultivars.

As with other fungus, daylily rust thrives in moisture. Use soaker hoses rather than overhead watering systems and water in the morning rather than late in the day or at night. This will cut down on the amount of time that the leaves remain wet.

Do not move or transport infected plant material. Carefully inspect incoming plant material for signs of rust. Fungicide applications are needed for disease management, especially on susceptible cultivars. Contact your local extension office for information on ratings of cultivar susceptibility and current fungicide control recommendations.

Daylily rust

Southern blight on plants is most likely to occur in the summer months when the soil is warm and moist. Symptoms include discolored lower leaves, wilted foliage, and plant collapse and it usually results in the death of the plant.

Preventing entry of the pathogen. Use of healthy, certified seeds of known origin. Careful cleaning of agricultural tools. Avoiding environmental conditions that favour development of the pathogen. Irrigation management. Plant density and growth habitats.

Soil solarization and certain organic amendments (e.g. composted chicken manure and rye-vetch green manure), as well as introducing certain Trichoderma spp. have also been shown to reduce plant death and number of sclerotia produced in the field in tomatoes. In addition to these cultural methods, chemical methods (e.g. fungicides) can also be employed.These methods all disrupt the production of mycelium and sclerotia, thus reducing the spread of disease.

Southern blight

General symptoms on the solanaceous crops and cucurbits include seed rot and seedling blight which discolors the roots and causes seedlings to topple over. Preemergence and postemergence damping-off are also possible symptoms that may occur.

Avoid overhead watering that can produce surface runoff, and consider slow drip irrigation instead. Hardy Phytophthora blight pathogens will survive in both hot summer and cold winter compost piles. Remove infected plants immediately, bag and dispose of infected debris, and always keep your garden clean.

Crop rotation may reduce the number of pathogens in the soil and, "a minimum of a 3 years crop rotation which alternates with non-host species is recommended to avoid build-up of P. capsici spores." Crops should also avoid conditions that would be conducive to the pathogen by using well drained soils and raised beds. As stated above, "Excess moisture is the single most important component to the initial infection and subsequent spreading of Phytophthora capsici. Overall, a study by K.H. Lamour and M.K. Hausbeck found that "crop rotation and mefenoxam are not likely to provide economic control". Mefenoxem is the active enantiomer contained in the racemic fungicide metalaxyl used to defend against Phytophthora capsici. Sexual recombination provides the genetic diversity to promote resistance towards fungicides in P. capsici. The failure of crop rotation as a means to control P. capsici may also be due to weeds playing the role of an alternative host in the absence of common hosts. According to a study done by the University of Florida, "In Florida, and perhaps elsewhere, weeds may contribute to pathogen survival in the absence of a host crop or when propagules may not readily survive in soil or plant debris." To avoid fruit rot of vegetable crops in the Cucurbitaceae, trellising cucurbit fruits and other ways to keep the fruit off the ground is a way to control secondary inoculants (zoospores) from physically being splashed from the soil onto the fruit. Control of Phytophthora capsici is easier in drier climates with less rainfall such as California. In these areas, it is important to practice placing drip irrigation emitters away from the stems of pepper plants in order to reduce the incidence of crown rot in peppers.

Phytophthora blight

Mealybugs have needle-like sucking mouthparts. Feeding activity can cause a yellowing of host leaves, distorted growth, premature leaf drop, and, with heavy populations, plant death. Mealybugs also produce large amounts of a sweet, sticky liquid waste product called honeydew. A black fungus called sooty mold may grow on the honeydew.

This pest is usually brought into the interiorscape on an infested plant. Therefore, one of the best ways to manage mealybugs on houseplants is to carefully check plants being considered for purchase and reject any infested plants. Quarantine new plants for 7-10 days in an isolated spot, and check for signs of mealybugs or other household pests before adding the plants to your interiorscape.
Provide proper cultural control so that the plants are vigorous and can tolerate moderate mealybug feeding without suffering too much damage. Do not over-water or over-fertilise — mealybugs are attracted to plants with high nitrogen levels and soft growth. Removing overwintering sites, such as loose bark, can help to reduce mealybug numbers. Predatory insects, such as lacewings, syrphid flies, ladybirds, and several small parasitic wasps, prey on outdoor mealybugs and can often keep their numbers down. An introduced beetle, Cryptolaemus montrouzieri, the mealybug destroyer, is available commercially for release in greenhouses. Avoid the unnecessary use of insecticide to minimise any adverse effect on these beneficial insects. Manage ants, which are attracted to honeydew produced by the mealybugs and will inhibit the activities of natural enemies.

1 Wash them away: Mealybugs can be dislodged with a steady stream of water. Repeat the treatment as necessary. This is best for light infestations.
2 Insecticidal soap: Insecticidal soaps are available on the market, or you can make your own by using a dish detergent such as Ivory Liquid. Try to find a product free of perfumes and additives that might harm plants. Mix the soap in a weak concentration with water (starting a 1 teaspoon per gallon and increasing as necessary). Spray on plants.
3 Neem oil: Neem oil is derived from the neem tree. Use according to label instructions. In addition to its insecticidal properties, neem is also a fungicide and has systemic benefits (meaning the plant absorbs it so it can control insects it doesn't directly contact). According to the Environmental Protection Association, neem is safe for use on vegetables and food plants as well as ornamentals.
4 Kitchen insect spray: This all-purpose insect spray. To make a batch, combine 1 garlic bulb, 1 small onion, and 1 teaspoon of cayenne pepper in a food processor or blender and process into a paste. Mix into 1 quart of water and steep for 1 hour. Strain through a cheesecloth and add 1 tablespoon of liquid dish soap. Mix well. The mixture can be stored for up to 1 week in the refrigerator.

Mealybug Pests

The earliest symptoms of rose rosette disease include a red pigmentation of the underside of leaf veins followed by sharply increased growth of vegetative shoots, which are typically more succulent than normal and colored in various shades of red. Leaves often become deformed, crinkled, and brittle with yellow mosaics and red pigmentation. As the disease progresses, leaves become very small, petioles are shortened, and most lateral buds grow, producing short, intensely red shoots. The disease causes the plant to be exceptionally susceptible to freeze damage. Symptoms on cultivated roses are typically less severe than on multiflora rose. Cultivated roses show symptoms of thickened, succulent stems and a proliferation of thorns. Symptoms can mimic some forms of herbicide damage.

Prune your roses in late winter or early spring. Do not use leaf blowers around your roses. Protect roses from prevailing winds with walls or other plants. Give your roses plenty of space. Control multiflora rose in your area.

1. Remove ornamental roses with symptoms. The entire plant including the roots should be removed and destroyed by burning or placing in a plastic bag. Care must be taken when working with diseased plants as you can facilitate spread of the mites that spreads the disease. Bag the plant before removal, cut it at ground level and then dig out the plant’s roots. Soil need not be removed. Clean tools and put on fresh clothing before moving to a disease-free plant or area. 2. Plant ornamental roses as far away as possible from known stands of multiflora rose. The general recommendation is maintain at least 300 feet between your roses and any stands of multiflora rose. Even greater distance is preferred especially if they are upwind of your desirable rose plants. 3. Control the disease by controlling the mite. Start mite control early by pruning your roses hard in late winter (back by 2/3) to remove as many overwintering mites as possible and then spray with horticultural oil to kill any remaining mites. Organic pesticides such as horticultural oils and insecticidal soap are recommended over other pesticides as these organic pesticides are less harmful to natural predators that feed on the problem mites. Apply weekly  during the months of June and July paying particular attention to the new growing tips where the mites will congregate. Refrain from using leaf blowers around roses as they can spread mites. 4. Help to isolate your roses. Do not plant roses too close together. With extra space between the plants mite movement can be reduced. Also, consider interplanting roses with other ornamental plants. 5. Using rose rosette disease as an IPM strategy. The multiflora rose is an exotic invasive species that is responsible for the degradation of millions of acres of farmland and recreational areas. Using the disease to control this invasive weed can cut costs and be considered environmentally friendly for reducing the amount of synthetic chemicals used. However, the disease also affects cultivated roses. One should be extremely cautious and good neighbor-minded when it comes to rose rosette disease.

Rose rosette disease

The first symptom is usually the appearance of minute yellow stippling on the upper surface of leaves that have mites on the undersides. Infested leaves generally become yellow and may drop off from plants. Red spider mites on the back of a leaf (left) and mite damage on a cucurbit leaf (right).

Host plant resistance can be a valuable component of an IPM system that is compatible with other control measures such as chemical control, and it makes beneficial natural enemies more effective. In many cases, even partially resistant cultivars are useful to enhance the efficacy of biocontrol agents.

Insecticidal soap or botanical insecticides can be used to spot treat heavily infested areas. On fruit trees, horticultural oil should be applied early in the season or late in the fall to destroy overwintering eggs. Dust on leaves, branches and fruit encourages mites.

Tetranychidae

Symptoms of infection include a downward curling of the leaves, leaf tip dieback, stunting, necrosis of growing leaf tips, sunken ‘chicken pox-like’ spots on leaves (often with a surrounding halo), stem death and yellowing. Since these symptoms are so generic, extreme caution must be taken when introducing new plants to your greenhouse. Infected plants can not be cured and not all hosts display visible symptoms.

Impatiens necrotic spot control focuses on excluding INSV and preventing its spread. Inspect any plants entering a greenhouse (e.g., new plant shipments, plants moved in from outdoors) for viral symptoms and thrips. Isolate new plants until they are determined to be thrips- and virus-free.

Once you suspect impatiens necrotic spot, treatment won't help – you must destroy the plant immediately. If many plants are infected, it's a good idea to contact your university extension office for testing to confirm the virus is present.

Impatiens necrotic spot virus

The spots on cucurbit leaves produced by the Phoma blight are usually more irregular in shape and most often are on the margin of the leaves. The spots are light brown on cantaloupe and cucumber and dark brown on watermelon. Fewer lesions are produced on stems but symptoms also tend to spread from the crown of the plant, giving the plant a blighted appearance. Fruit are generally not affected.

Crop rotations with nonhost plants such as small grain, corn, of two or more years are effective in reducing the incidence if disease-free seed are used. Currently no varieties are resistant.

A fungicide such as benomyl (Benlate), chlorothalonil (Bravo), copper, maneb (Manzate D or Dithane M-22 Special), mancozeb (Dithane M-45 or Manzate 200) or Dikar (Polyram) may be used to control the disease in the field. It is important to start the spray schedule as soon as the plants emerge and spray at 7-10 day intervals, covering all plant surfaces. High pressure (400 psi), high volume (100 gal/acre for a mature crop) spray equipment provides most effective coverage.

Phoma blights

Fungus gnat damage will appear similar to that of any other root-related issue, such as root rot. Lower leaves may turn yellow and drop, and the plant’s growth may slow down or stop completely. In particularly bad cases, wilting of the entire plant could occur, followed by the death of the plant if roots are extremely damaged. 
In small numbers, fungus gnats are more of an annoyance than anything. In fact, the adult gnats don’t actively harm plants nor people. If their population gets out of hand, however, the larvae may start feeding on plant roots, causing notable damage. This is especially bad for young plants, such as seedlings, which have only a few delicate roots. Fungus gnats are also capable of spreading the plant pathogen that causes damping off and the eventual death of seedlings.

1. Keep soil dry: Fungus gnats seek out moist soil, so allowing your houseplants to dry out a bit between waterings can slow down or stop an infestation. Let the top inch or two of soil dry out before watering again, and try to go as long as possible between waterings. Gnats may be deterred from laying their eggs if the soil is dry on the surface.
2. Mosquito dunks (with beneficial bacteria): Mosquito dunks are used to keep mosquito larvae from populating fountains, animal troughs, fish ponds, and other small bodies of water. The product consists of a dry pellet containing a type of bacteria called Bacillus thuringiensis subspecies isrealensis. This beneficial bacteria infects and kills the larvae of flying insects, including mosquitoes, fruit flies, and fungus gnats.
To use mosquito dunks: Fill up a gallon jug (or watering can) with clean water and toss in a mosquito dunk. It’s a good idea to break up the dunk a bit before placing it in the water, or you can wait for it to soften before breaking it apart. Let the dunk soak in the water for as long as possible (at least overnight), then remove it from the water (the dunk can be reused) and use this water for fungus gnat–infested plants. The bacteria will have leeched into the water and will now infect and kill any larvae that come into contact with it in the soil. Repeat this process every time you water your plants for at least a few months.
3. Cover drainage holes: Though gnats typically remain near the tops of pots, they may find their way to the drainage holes on the underside of a pot and start laying eggs there, too. If this happens, cover the drainage holes with a piece of synthetic fabric to prevent the gnats from getting in or out of the hole, but to also let water pass through freely. Attach with tape or rubber bands.

Getting rid of fungus gnats is all about consistency. Catching the adults is fairly easy, but because the adult population comes in cycles, you need to make sure that your traps are refreshed regularly. For the best results, use a combination of the traps :
1. Sticky cards traps: These traps consist of a yellow note card covered in a sticky adhesive. They are most effective when cut into small squares and placed directly on top of the soil or attached to skewers just above the soil. Adult gnats will fly or crawl onto the card and become trapped. Fungus gnats are attracted to the color yellow, so use the yellow sticky cards rather than the blue ones. 
2. Cider-vinegar traps: Simple and effective, cider-vinegar traps consist of a shallow container with a small amount of apple cider vinegar, water, and liquid dish soap.
To make a cider-vinegar trap: Find a shallow container—a tuna can is perfect—and fill it with equal parts water and apple cider vinegar. (The liquid should be at least ¼-inch deep.) Put a few drops of liquid dish soap into the mixture and stir gently. Place the trap near the base of the affected plant or, ideally, inside the pot on top of the soil. Check it every few days to refresh with new vinegar and water.
3.Flypaper: Flypaper ribbons, such as those hung in horse barns to catch outdoor flies, can also be used to catch fungus gnats. However, these traps are usually overkill for gnats and can easily get stuck to things you don’t want them to stick to, such as furniture, hair, plants, and so on.

Fungus Gnats

These weevils are pests of over 100 plants, ranging from weeds to shrubs to greenhouse plants. Some of the common host plants in Maryland include azalea, holly, strawberry, rhododendron, yew, and grape.
When weevils are present in low numbers only a few notches on the edges of leaves will be apparent. If many weevils are present, the leaves are often scalloped and left with only the main vein.
The grubs are highly destructive to plants. When small, grubs consume feeder roots. Larger grubs feed on larger roots, stripping the bark and sometimes girdling the plant crown. This blocks the flow of water and nutrients to the foliage.
Infested plants have stunted growth; leaves turn yellow and then wilt.

1 Quarantine or dispose of any soil from pots where vine weevil have been found. Don't reuse this or throw on the garden because it may still contain vine weevil eggs, larvae or pupae.
2Remove plants that have unexplainably wilted and died and examine the roots. If they appear eaten, then search the surrounding soil and destroy any vine weevil larvae that you find.
3 Look for leaf edge notching on garden plants to indicate where adult vine weevils are feeding. Then treat the surrounding soil with nematodes during the summer months to control any larvae that appear.
4 Avoid using broad spectrum insecticides which will kill soil-dwelling predators of vine weevil larvae, such as centipedes and carab beetles.
5 Encourage insectivorous birds by hanging feeders in winter and provide nesting boxes in spring.

- Check plants every week to prevent weevil infestations becoming out of control and deal with early signs immediately.
- Remove and destroy newly-hatched adults to reduce the numbers of eggs laid in the soil. This is best done at night, with a torch, when the weevils are most active.
- Use netting and fleeces to stop adults moving between plants and laying eggs within pots.
-Replant perennial pot plants in the spring and look for and remove any vine weevil larvae you find.
- Use commercially available nematodes (microscopic worm-like creatures) Steinernema kraussei and Heterorhabditis megidis that can be watered into pots or surrounding soil to control vine weevil larvae. The nematodes seek out and kill vine weevils.
- BotaniGard ES is a highly effective biological insecticide containing Beauveria bassiana, an entomopathogenic fungus that attacks a long-list of troublesome pests – even resistant strains! Weekly applications can prevent insect population explosions and provide protection equal to or better than conventional chemical pesticides.
- Fast-acting crack and crevice sprays, like Don’t Bug Me, can be used around windows, doors and vents to prevent adult weevils from entering structures.
- Least-toxic botanical insecticides should be used as a last resort. Derived from plants which have insecticidal properties, these natural pesticides have fewer harmful side effects than synthetic chemicals and break down more quickly in the environment.

Weevils

A sign of plant disease is physical evidence of the pathogen. For example, fungal fruiting bodies are a sign of disease. When you look at powdery mildew on a lilac leaf, you’re actually looking at the parasitic fungal disease organism itself (Microsphaera alni). Bacterial canker of stone fruits causes gummosis, a bacterial exudate emerging from the cankers. The thick, liquid exudate is primarily composed of bacteria and is a sign of the disease, although the canker itself is composed of plant tissue and is a symptom.

Good gardening habits and effective treatment help prevent, stop and control fungal disease
1. Start by planting healthy stock. 
2. Choose planting sites based on plant needs. 
3. Avoid overhead watering. 
4. Water early in the day. 
5. Don't crowd plants. 
6. Don't work a wet garden. 
7. Treat with a trusted, proven fungicide.

Baking soda, soap, and water is one of the safer ways to treat plant fungus issues, especially if the affected plants are inside your home. You really don't want to be spraying fungicide all over the inside of your home if you can avoid it!

Fungi

Leaf curl and distortion. Leaf yellowing or stippling. Necrotic leaf spots. White sporulation of the pathogen on lower leaf surface. Defoliation.

Use hygiene measures. Start clean, remove crop residues and prevent splashing water.

One way to control downy mildew is to eliminate moisture and humidity around the impacted plants. Watering from below, such as with a drip system, and improve air circulation through selective pruning. In enclosed environments, like in the house or in a greenhouse, reducing the humidity will help as well.

Peronosporea

Some of the most common symptoms of nutrient deficiencies are chlorosis, foliage color changes, overall plant stunting and sometimes necrosis. All can be caused by one or more deficiencies.

Monitor pH Levels – There are lots of things that can cause a hydroponic nutrient solution to drift outside of the ideal range of about 5.6. Usually, if a nutrient solution is left unmonitored for too long, it can start drifting outside of this range because it gets too dense in raw, use nutrients. Other times, it might start becoming too acid or too alkaline when you add new hydroponic nutrients or transfer your plants to a new medium. Since pH levels can change very rapidly, it is important to check your pH level daily. The longer your nutrient solution spends outside of this ideal range, the greater the chance that your flowers or vegetables will suffer a plant deficiency. Use a pharmaceutical grade pH adjustment product designed specifically for hydroponics to make the necessary adjustments. This way you have less of a chance of accidentally over compensating your pH adjustments.  Keep Temperature Levels Stable – Your nutrient solution should be fairly cool to temperate, somewhere in the range of sixty six to seventy one degrees Fahrenheit. You should be particularly aware of this if you happen to live in an unusually warm or cold part of the world. If you feel it is necessary to prevent plant deficiency, take extra steps insulate your grow room against outside elements. You should also avoid placing your reservoir directly on the ground in your grow room, as the floor can be very cool, which can transfer to the reservoir and cause a plant deficiency.

When the temperature of your indoor garden or the nutrient solution falls below 55 degrees Fahrenheit, plants take up less phosphorus than they need. If you've determined that the temperature is not the problem, treat your plants to bone meal, a supplement that's rich in phosphorus.

Nutrient deficiency

Wilted, downward-hanging foliage is often the first obvious symptom of Armillaria root rot. Other symptoms include foliage yellowing, leaf drop, and dieback of upper limbs. During the rainy fall and winter, groups of short-lived mushrooms often grow around the base of Armillaria-infected trees.

Cultural practices can also be effective for preventing the spread of Armillaria. High temperatures interfere with the progression of this disease; if soil temperatures reach 79 °F (26 °C), then the growth of Armillaria in the soil will be limited. Using collar excavation to expose primary roots directly below the crown to the continuous cycle of solar heating and air may reduce the colonization from Armillaria in trees that are already infected. This is called root collar excavation (RCE), and while it has been applied to citrus orchards and grapevines, this method has high labor costs and involvement due to the difficulty of carefully exposing these primary roots.

Sadly, there is no absolute treatment for Armillaria root rot. The disease can be managed by the consistent removal of dead trees and infected stumps. Armillaria requires consistent moisture to survive, and in citrus groves, excavation around the root crown has been an effective deterrent but not an ultimate cure.

Armillaria root rot

Springtails occasionally feed on plant roots, but the damage is minimal. Problems arise when these pests congregate in moist areas and multiply. Thousands of springtails blanket walls, foundations and patios as their numbers grow. If not stopped outdoors, springtails multiply indoors in damp basements, kitchens and bathrooms — anywhere with sufficient moisture.

It is not difficult to keep this insect at bay. First of all ensure that house plants are always grown in sterile potting compost (this will also help keep away the diseases that the soil can contain).
If there is insufficient drainage, the compost can become waterlogged, so, next, always ‘crock’ a pot with a layer of grit or clay pellets before adding compost. If the compost to be used is too compact, coarse sand or perlite can be added to make it more free-draining.
If you find it difficult to assess when to water use a moisture meter, a self-watering cone or a container with a reservoir. In the latter cases, the compost takes up water gradually as it dries out, ensuring an even supply.

1 First of all, stop watering the plant and allow it almost to dry Out before re-watering. ‘This may be enough to eradicate these pests. It not, then you will need to use a chemical.
2 Use a suitable chemical, in granule form or diluted with water, to soak the potting mixture.
3 Insecticides containing diazmon, lindanc, malathion, pyrethrum or resmethrin are suitable. Make sure that due ingredients of an insecticide are listed on its label. One application of the chemical should be enough but repeat the application after 8 days to ensure eradicating ideal conditions for springtails.
4 If your plants are infested with Springtails, you will know as soon as you water them, as these tiny insects will start jumping about on top of the potting mixture.
5 Springtails will thrive in waterlogged soil so always water very carefully and ensure that the plant has good drainage.

Springtails

Black mold is characterized by obvious lesions that appear on the surface of ripe fruit. Lesions are light to dark brown and vary from small flecks affecting only epidermal tissue to large, more or less circular, sunken lesions with decay extending into the carpel wall and often into the seed locule. During warm, humid weather the fungus may sporulate to form a black, velvetlike layer on the surface of the sunken lesions.

Select resistant varieties of plants/crops that are less susceptible to important pathogens. Pathogens reproduce at higher rates on susceptible varieties compared with resistant or partially resistant varieties. Cultural practices grapeCapitalize on cultural practices to reduce the pathogen population or create conditions less favorable for the pathogen to develop. When fewer non-chemical control methods (such as sanitation) are used, resistance is more likely to develop, or will develop more rapidly. Monitor and maintain agronomic factors such as soil moisture and crop nutrition, and manage other pests, to avoid crop stress throughout the season.Inadequate or excessive fertilization with nitrogen may increase disease incidence in some crops.  For example, early blight of potato and tomato and dollar spot of turfgrass are favored by nitrogen deficiency.  Alternatively, the severity of spring dead spot of bermudagrass and some foliar diseases of wheat is increased with intensive nitrogen fertilization. Excessive irrigation or frequent irrigation with small amounts of water increases the incidence of many diseases by promoting spread of the pathogen and extending periods of leaf wetness, and high soil moisture. Rotate crops to allow greater flexibility in choosing different tillage practices and/or the use of fungicides with different MOAs. Be aware that applying a fungicide unnecessarily to a crop in one year in the absence of fungus could result in undesirable effects on pathogens of rotational crops. NOTE: It is possible to rotate different crops between years and, yet, still use the same fungicide MOA to control the same disease. When one crop can serve as a source of inoculum for a subsequent crop, the alternation scheme among at-risk fungicides should be continued between successive crops such that the first at-risk fungicide applied to a crop belongs to a different group than the last at-risk fungicide applied to the previous crop.Be aware that resistant plant pathogens can spread from nearby fields, highways, railroads, or utility rights-of-way areas near your farm or treated site. Local and regional cooperation in resistance management is essential. Participate in Extension programs that conduct area-wide monitoring for the presence of disease pathogens and potential resistance development. Submit reports of fungicide control failures so that the possibility of resistance can be monitored and evaluated.

Fungicides are pesticides that kill or prevent the growth of fungi and their spores. They can be used to control fungi that damage plants, including rusts, mildews and blights. They might also be used to control mold and mildew in other settings.

Alternaria black molds and stem cankers

Nymphs and adults feed on plant juices, attacking leaves, stems, buds, flowers, fruit, and/or roots, depending on the species. Most aphids especially like succulent new growth. Some, such as the green peach aphid, feed on a variety of plants, while others, such as the rosy apple aphid, focus on one or just a few plant hosts.
- Look for misshapen, curling, stunted, or yellowing leaves. Be sure to check the undersides of leaves; aphids love to hide there.
- If the leaves or stems are covered with a sticky substance, that is a sign that aphids may have been sipping sap. This “honeydew,” a sugary liquid produced by the insects as waste, can attract other insects, such as ants, which gather the substance for food. When aphids feed on trees, their honeydew can drop onto cars, outdoor furniture, driveways, and so on.
- The honeydew can sometimes encourage a fungal growth called sooty mold, causing branches and leaves to appear black.
- Flowers or fruit can become distorted or deformed due to feeding aphids.
- Some aphid species cause galls to form on roots or leaves.
- Aphids may transmit viruses between plants, and also attract other insects that prey on them, such as ladybugs.

- For fruit or shade trees, spray dormant horticultural oil to kill overwintering aphid eggs.
- Beneficial insects, such as ladybugs, lacewings, and parasitic wasps, will feed on aphids. Supplemental populations of these insects can be ordered online and should help keep the aphid populations controlled from the start.
- Companion planting can be very helpful to keep aphids away from your plants in the first place. For example:
1 Aphids are repelled by catnip.
2 Aphids are especially attracted to mustard and nasturtium. Plant these near more valuable plants as traps for the aphids. (Check your trap plants regularly to keep aphid populations from jumping to your valued plants.)
3 Nasturtiums spoil the taste of fruit tree sap for aphids and will help keep aphids off of broccoli.
4 Garlic and chives repel aphids when planted near lettuce, peas, and rose bushes.

- Try spraying cold water on the leaves; sometimes all aphids need is a cool blast to dislodge them. Typically they are unable to find their way back to the same plant.
- If you have a large aphid invasion, dust plants with flour. It constipates the pests. 
- Neem oil, insecticidal soaps, and horticultural oils are effective against aphids. Be sure to follow the application instructions provided on the packaging.
- You can often get rid of aphids by wiping or spraying the leaves of the plant with a mild solution of water and a few drops of dish soap. Soapy water should be reapplied every 2-3 days for 2 weeks.
- One variation of this soap-water mix includes cayenne pepper: Stir together 1 quart water, 1 tsp liquid dish soap, and a pinch of cayenne pepper. Do not dilute before spraying on plants.
- Diatomaceous earth (DE) is a non-toxic, organic material that will kill aphids. Do not apply DE when plants are in bloom; it is harmful to pollinators, too.

Aphids

Yellowing (Chlorosis) occur in the newly emerging leaves instead of the older leaves and usually seen in the interveinal region Fruit would be of poor quality and quantity. Chlorosis occurs in younger leaves because iron is not a mobile element, and as such, the younger leaves cannot draw iron from other areas of the plant. Over time, the yellowing may even turn a pale white or the whole leaf may be affected. Iron deficient plants may overaccumulate heavy metals such as cadmium. Any plant may be affected, but raspberries and pears are particularly susceptible, as well as most acid-loving plants such as azaleas and camellias.

Prevention is the best control. Do not plant chlorosis-susceptible trees in soils having a high pH or in soils low in organic matter. If practical, replace species that are susceptible. When the leaves of plants become chlorotic, always determine the primary cause through a soil test.

Iron deficiency can be avoided by choosing appropriate soil for the growing conditions (e.g., avoid growing acid loving plants on lime soils), or by adding well-rotted manure or compost. If iron deficit chlorosis is suspected then check the pH of the soil with an appropriate test kit or instrument. Take a soil sample at surface and at depth. If the pH is over seven then consider soil remediation that will lower the pH toward the 6.5 - 7 range. Remediation includes: i) adding compost, manure, peat or similar organic matter (warning. Some retail blends of manure and compost have pH in the range 7 - 8 because of added lime. Read the MSDS if available.) ii) applying Ammonium Sulphate as a Nitrogen fertilizer (acidifying fertilizer due to decomposition of ammonium ion to nitrate in the soil and root zone) iii) applying elemental Sulphur to the soil (oxidizes over the course of months to produce sulphate/sulphite and lower pH). Note: adding acid directly e.g. sulphuric/hydrochloric/citric acid is dangerous as you may mobilize metal ions in the soil that are toxic and otherwise bound. Iron can be made available immediately to the plant by the use of iron sulphate or iron chelate compounds. Two common iron chelates are Fe EDTA and Fe EDDHA. Iron sulphate (Iron(II) sulfate) and iron EDTA are only useful in soil up to PH 7.1 but they can be used as a foliar spray (Foliar feeding). Iron EDDHA is useful up to PH 9 (highly alkaline) but must be applied to the soil and in the evening to avoid photodegradation. EDTA in the soil may mobilize Lead, EDDHA does not appear to.

Iron deficiency

Canker, plant disease, caused by numerous species of fungi and bacteria, that occurs primarily on woody species. Symptoms include round-to-irregular sunken, swollen, flattened, cracked, discoloured, or dead areas on the stems (canes), twigs, limbs, or trunk.

Control includes removing diseased parts in dry weather; growing adapted or resistant varieties in warm well-drained fertile soil; avoiding overcrowding, overwatering, and mechanical wounds; treating bark and wood injuries promptly; controlling insect and rodent disease carriers; wrapping young trees to prevent.

The main measures for controlling the residue are the destruction of vegetation after harvest; cutting and burning of plant parts most severely damaged by anthracnose; spraying with 1% Bordeaux liquid.

Canker

Leaf spots will begin as very small, yellow, brown or black spots that enlarge in size. The spot usually turns gray with a black outline. Lesions on the petiole and rachis are similar. Symptoms may occur on multiple leaves at once, especially on juvenile palms.

Fungicides are used to prevent further spread of the disease by protecting leaf tissue that has not been infected by the fungal pathogen. In the nursery situation, prune severely diseased leaves prior to fungicide application.

In rare cases of severe infection and where the size and value of plants make it practicable, applications of fungicides may be helpful.

Pestalotiopsis leaf spot

Typical leaf symptoms of viral diseases include mosaic patterns, chlorotic or necrotic lesions (Figure 13), yellowing, stripes or streaks, vein clearing, vein banding, and leaf rolling and curling.

Remove all infected plants and destroy them. Do NOT put them in the compost pile, as the virus may persist in infected plant matter. Burn infected plants or throw them out with the garbage. Monitor the rest of your plants closely, especially those that were located near infected plants. Disinfect gardening tools after every use. Keep a bottle of a weak bleach solution or other antiviral disinfectant to wipe your tools down with.

1. Remove all infected plants and destroy them. Do NOT put them in the compost pile, as the virus may persist in infected plant matter.
2. Monitor the rest of your plants closely, especially those that were located near infected plants.
3. Disinfect gardening tools after every use.

Viruses

Bacterial leaf spots show as necrotic, circular or angular lesions and may have a yellowish outline or halo. Early symptoms of bacterial leaf spots show on older leaves and lesions appear water-soaked. Bacterial spots affecting dicytyledounous plants that have net-like leaf veins sometimes take a more angular shape as they are restricted by the large leaf veins. Bacterial spots on monocotyledonous plants with parallel leaf veins have a streak or striped appearance. The most obvious symptom of bacterial leaf spots are the blackening of the spots after infection. Eventually older lesions dry out and become papery in texture. Bacterial spots can also produce white, yellow, light cream or silver bacterial exudate depending on the type of bacteria, which may ooze from splitting lesions and/or from the underside of the spots. Bacterial leaf spots caused by Pseudomonas show red-brown spots which can distort the infected leaves, whilst those caused by Xanthomonas are angular or circular in shape outlined with a yellow halo.

Prevention of leaf spot disease includes variety selection, crop rotations, plant hygiene and fungicide use for seeds and foliage. To stop the spread of pathogens good sanitation is key as well as the avoidance of handling plants when wet, planting pathogen-free and resistant cultivars and moving out infected plants. Reducing the humidity around plants and in greenhouses by good plant spacing for air circulation, and watering early in the day can also help prevent leaf spot disease. Disinfection of tools and washing of hands is important when handling infected plants. Susceptibility to leaf spot disease can occur due to insufficient or excessive fertilising of plants. Checking plants periodically for any signs and symptoms of disease is also good practice. Avoiding overhead watering and increasing air circulation by pruning plants should be done to prevent humid conditions. Collecting and removing fallen leaves is important in reducing the amount of pathogenic agents on the ground to prevent dispersal of disease.

Certain chemicals are used to treat leaf spot disease, such as the Bordeaux mixture, the first fungicide to have been developed, which treats many fungal and bacterial leaf spots. Other fungicides such as zineb, chlorothalonil and Captan, also treat leaf spot disease and Benomyl specifically treats Cercospora leaf spots, cherry leaf spot and black spot of roses. Thiabendazole is used to treat leaf spot diseases of turf and ornamentals. Both fenarimol and nuarimol are pyrimidines that also treats leaf spot disease. More chemicals include Triazoles an organosphosphate fungicide, Imazalil, Procholora and Fentin hydroxide. Registered fungicides in use are thiophanate methyl, chlorothalonil, ferban and mancozeb.

Bacterial leaf spot

The signs of damage vary, typically depending on the way that the insect feeds on the plant. Damage from insects with chewing mouthparts typically appears on leaves or stems as ragged edges, holes, or other missing tissue. Insects that often cause chewing damage include caterpillars and Eastern lubber grasshoppers.

Preventing the transmission of viruses can be the chief reason to control certain insects. An example is the importance of controlling western flower thrips when growing impatiens. Their transmission of tomato spotted wilt virus can devastate a crop being started in a greenhouse.

The most common way of damaging the crops is through direct injury, caused by feeding on above-ground and below-ground plant parts. This type of direct crop injury is related to the insect's mouthparts. For example, insects with chewing mouthparts, such as beetles, damage the crop by chewing the leaves or some other plant parts. Moreover, some of them cause damage by boring into the plant tissue, such as stem boring insects or leaf miners.

Feeding damage by insects

Galls are most commonly found near ground level on the roots and lower branches of the plants. As the galls enlarge, they become woody and hard. The outer layer turns brown and corky. The plant may be weakened and stunted with some branch or tip dieback. Symptoms may not develop immediately after infection. Galls grow most rapidly during the warm months of the year.

Limit wounding of plant material. Avoid planting too deep. Avoid mounding soil up on newly planted trees. Keep crown of tree as dry as possible; Agrobacterium is favored by wet environments.

1. Prune out infected material. Crown gall cannot be eliminated from a shrub even though the infected plant may live for many years. To improve the appearance of the plant, prune out and destroy infected stems below the galled area. Sterilize the pruning shears after each cut with a mixture of one part bleach to nine parts water. 2. Destroy infected plants. Destroy the infected plant. The bacterium will remain in the soil so it is important to plant a resistant plant species. If the same species needs to be planted in the area, remove and replace the soil or consider soil sterilization. 3. Sterilize the soil. Soils known to be infected with crown gall bacteria can be sterilized using chemicals, heat, or antibiotics. This is not practical for most home gardeners. A biological control has been introduced using a bacterium, Agrobacterium radiobactor strain 84. This bacterium was discovered to be antagonistic to crown gall bacterium. It is available for use as a preplant treatment by dipping nursery stock in a suspension of the live bacteria in water. 4. Exclude the problem. When purchasing forsythia and euonymus plants, inspect them carefully for signs of galls. Do not purchase plants that show gall-forming symptoms. 5. Replant with a more resistant plant species. The following plants recommended by the University of Illinois show greater resistance to bacterial crown gall: barberry, hornbeam, true cedars, ginkgo, golden raintree, tulip tree, mahonia, spruce, linden, boxwood, catalpa, beech, holly, larch, magnolia, black gum, pine, Douglas fir, bald cypress, hemlock, birch, firethorn, redbud, smoke tree, sweet gum, deutzia, serviceberry, yellowwood, yew, and zelkova.

Crown gall

All members of the class produce basidiocarps which range in size from tiny cups a few millimeters across to a giant polypore (Phellinus ellipsoideus) greater than several meters across and weigh up to 500 kilograms (1,100 lb). Agaricomycetes produce mushrooms, and are therefore the most familiar and conspicuous of all Fungi. Other Fungi produce macroscopic fruiting bodies as well, but the diversity of forms in the Agaricomycetes is unmatched.

A proven fungicide that prevents disease from becoming active and treats it quickly is a crucial part of your protection plan. GardenTech® Daconil® Fungicide, with the active ingredient chlorothalonil, provides protection against a broad spectrum of fungal pathogens and simplifies controlling fungal disease from your garden.

Used as a preventive and an active treatment, Daconil® Fungicide can prevent, control or stop more than 65 types of fungal disease on flowers, vegetables, shrubs, fruit and shade trees.

Agaricomycetes

Leaves Go Yellow and Fall Off. Dropping Old and New Leaves Alike.  Wilting, Limp Leaves. Leaves Turning Splotchy Black or Dark Brown.  Mushy Roots Mean Overwatering.  An Overwatered Succulent Will Rot and Turn Mushy.

Soaking the ground for a longer period of time less often, and not watering by hand but using a sprinkler or soaker hose, is the way to handle that situation. Mulch around the plant will also help keep a more even level of moisture.

Move your plant to a shady area even if it is a full-sun plant. Remove any dead or dying leaves. These should be easily recognizable. Check your pot for proper drainage and, if possible, create additional air space around the roots. This will allow oxygen to reach the root zone. Remove any dead or dying roots and keep only the roots that are healthy. Water only when the soil is dry to the touch, but do not let it get too dry. You should also seize all fertilization at this point until the plant is healthy again. Treat with a fungicide.

Water excess and/or uneven watering

Plant stunting and severe curling of leaves occur when the leafhopper Empoasca fabae punctures the undersurfaces of leaves and veins of bush beans and inhibits growth. This leafhopper also feeds on alfalfa and causes leaves to turn yellow and drop off.

Try to avoid moisture or humidity relationships as they affect the habitats of homopterans.

When controlling thrips, you can prune and get rid of any injured areas on the plant. Regular pruning helps get rid of thrips. Thrips on flowers can be eliminated as soon as you see signs of damage by using a mild insecticide like insecticidal soap or neem oil, or by pruning the flowers.

Homoptera

In the fruits, black or brown lesions (e.g., on pods, scab, and pitting) are common. Infection on the inflorescence produces blight, necrosis, and lesions with flecks and streaks. Infected leaves produce abnormal colors and patterns with dark, necrotic, angular, or irregular areas.

Plant resistant plants, or buy healthy transplants. Plant your plants in well-drained soil.  Water your plants with a drip sprinkler, as opposed to an overhead sprinkler.. Keep ripening fruits from touching the soil. Remember to rotate your plants every 2 to 3 years.

The best control products were Daconil Ultrex (chlorothalonil), Pageant (pyraclostrobin and boscalid) and Spectro 90WDG (chlorothalonil and thiophanate methyl). In addition, mancozeb (i.e., Dithane and Pentathlon) or copper were also very effective when used preventively.

Colletotrichum

Browning of leaf margins and/or yellowing or darkening of the areas between the main leaf veins are symptoms of leaf scorch. Due to environmental causes, leaves may dry, turn brown, and become brittle. Look for damage to trees and shrubs on the upper portion on the sunny, southern side and on the windy side. Premature dropping of leaves and twig dieback may occur during the late summer. Symptoms usually appear after drying winds in conjunction with periods of hot, dry weather. Leaf scorch on narrow leaf evergreens appears as brown or purple brown discoloration of the needle tips. If unfavorable conditions become more severe, browning of needles increases. This should not be confused with the browning and shedding of older interior needles. Scorch may result from hot, dry weather in summer or from strong, dry winter winds when the ground is frozen. Symptoms may not become apparent for a month or more after the initial injury. Winter leaf scorch in evergreen plants usually appears as two long, brown areas paralleling the main leaf vein.

1. Plant Thoughtfully. Even your plants that love to soak up the sun need some form of shade to protect them.
2. Use Sunblock. If you can't provide your plants the amount of shade they need, use another method to keep them insulated and keep moisture in the soil around them.
3. Create Shade.

1. Water when needed and maintain plant vigor. Plant in a fertile, well-drained soil at the same depth the plants grew in at the nursery and with an adequate supply of organic matter. Soil should be moist to a depth of 10 to 12 inches after a thorough watering. This should be done about once weekly. It is very important for the trees, especially broadleaf and needled evergreens, to be well watered going into the winter period. Water during this period if seasonal rains are not adequate or during the winter when the soil is not frozen. Annuals and perennials require more frequent watering than most trees and shrubs. 
2. Fertilize. Fertilize plants in early spring based on a soil test and the directions printed on the fertilizer container. Nitrogen should be applied annually based on the area to be fertilized, the type of plant, and the diameter of the trunk. Do not fertilize with nitrogen in the late fall as it may cause new soft growth easily damaged by cold weather. 
3. Mulch. Organic mulches (pine needles, wood chips, composted leaves, pine bark, cypress mulch) can help retain moisture during the summer and fall droughts. In the winter this mulch prevents the alternate freezing and thawing of the soil. Mulch will also cool the soil in summer. 
4. Screens. Screens may be used to protect trees and plants in areas exposed to wind and sun, but it is best not to plant tender plants in these exposures. 
5. Exposure. Other factors which can result in scorch are excessive fertilizer, deicing salt, herbicide, dog urine, trash fires, leaking sewer or gas mains, girdling roots or strangling wires, vehicle exhaust, and heat reflected from buildings. Elimination of the exposure to these elements is the only correction. 
6. Physical hazards. Avoid root injury when digging near trees and shrubs. Care should be taken to not injure the bark and roots when using lawnmowers, weed whips, and edging tools.

Sunburn

Symptoms vary across plant organs and tissues. B. cinerea is a soft rot that will have a collapsed and water soaked appearance on soft fruit and leaves. Brown lesions may develop slowly on undeveloped fruit. Twigs infected with gray mold will die back. Blossoms will cause fruit drop and injury, such as ridging on developing and mature fruit. Symptoms are visible at wound sites where the fungus begins to rot the plant. Gray masses with a velvety appearance are conidia on the plant tissues are a sign of plant pathogen. These conidia are asexual spores that will continue to infect the plant and surrounding hosts throughout the growing season making this a polycyclic disease. Plants can produce localized lesions when a pathogen attacks. An oxidative burst causes hypersensitive cell death called a hypersensitive response (HR). This soft rot can trigger HR to assist in colonization. Botrytis cinerea, as a necrotrophic pathogen, exploits the dead tissue for its pathogenicity or its ability to cause disease. Susceptible plants cannot use the HR to protect against Botrytis cinerea.

The best way to prevent gray mold is to space out plants so they have room to dry out after rain or watering. Remove infected flowers, leaves and stems. Infected plant parts should be buried or composted. Many flowering plants can recover from gray mold when warm, dry conditions return.

Prune or stake plants to improve air circulation between plants. · If growing indoors use a small clip-on fan to improve air flow.

Gray mold

Symptoms usually involve necrotic, often water-soaked leaf spots, typically most severe on lower leaves. The spots may be very small at first but develop an angular shape as the movement of the bacteria is limited by leaf veins. Eventually several spots may enlarge, coalesce and cause death of mature leaves.

Reduce humidity to encourage dry foliage and avoid dripping within the greenhouse. Avoid splashing water from plant to plant.  Avoid excess moisture and late day irrigation.

Chemical treatments work best as a preventive measure. Copper-based plant protection products have bactericidal activity (kill bacteria) and can be effective. Disinfection products that contain hydrogen peroxide or quaternary ammonia are also available.

Gammaproteobacteria

Yellowing between the leaf veins, sometimes with reddish brown tints and early leaf fall. Magnesium deficiency is common in tomatoes, apples, grape vines, raspberries, roses and rhododendrons.

Reducing or avoiding calcium-rich foods two hours before or after eating magnesium-rich foods. avoiding high-dose zinc supplements. treating vitamin D deficiency. eating raw vegetables instead of cooking them. quitting smoking.

Epsom salts dissolved in water and sprayed onto foliage and applied around the roots will cure magnesium deficiency. In future, feed plants in spring with balanced plant food that contains magnesium. For rhododendrons and azaleas, feed with a plant food specifically formulated for lime-hating or ericaceous plants.

Magnesium deficiency

The typical signs are brown or black feeding punctures visible on the affected plant tissues. Another conspicuous sign is honey dew, a sweet excretion that is released by the sucking insect. Often ants are attracted to feed on the honey dew.

Most true bugs do not cause serious harm to established plants. Provide proper cultural care so plants are vigorous. Provide adequate irrigation. Avoid growing shade-adapted species in full sunlight.

Effective ways to get rid of these stink bugs include sealing the house, dusting treatment, spraying with nicotine water, and using insect repellents. Stink bugs, also referred to as shield bugs, are a group of flying insects that belong to the Pentatomidae family of the order Hemiptera.

Hemiptera

Symptoms of Tobacco Rattle Virus vary based on the plant host, which differs widely in this disease. Common symptoms include mottling, cholortic or necrotic local lesion, ringspots or line patterns, and systemic necrosis.

Abandon fields highly infested with TRV.  Avoid planting TRV-sensitive cultivars. Use virus-free seed. Practice crop rotation using TRV non-host crop alfalfa Control weeds to lower the viruliferous stubby root nematode numbers.

Once plants have become infected with TRV, they remain infected indefinitely. Infected plant cannot be treated in any way to eliminate the virus and should be removed and disposed of by burning, burying or composting.

Tobacco rattle virus

When late blight infects stems, everything above the infection site dies. Infected tomato fruits develop rough, leathery spots or dark, water-soaked areas that rot rapidly. Potato tubers bear dark, irregular spots on the surface and reddish-brown spots that extend down into the flesh. Decay continues after harvest.

Fungicides for the control of potato blight are normally only used in a preventative manner, optionally in conjunction with disease forecasting. In susceptible varieties, sometimes fungicide applications may be needed weekly. An early spray is most effective. The choice of fungicide can depend on the nature of local strains of P. infestans. Metalaxyl is a fungicide that was marketed for use against P. infestans, but suffered serious resistance issues when used on its own. In some regions of the world during the 1980s and 1990s, most strains of P. infestans became resistant to metalaxyl, but in subsequent years many populations shifted back to sensitivity. To reduce the occurrence of resistance, it is strongly advised to use single-target fungicides such as metalaxyl along with carbamate compounds. A combination of other compounds are recommended for managing metalaxyl-resistant strains. These include mandipropamid, chlorothalonil, fluazinam, triphenyltin, mancozeb, and others. In the United States, the Environmental Protection Agency has approved oxathiapiprolin for use against late blight.

Ridging is often used to reduce tuber contamination by blight. This normally involves piling soil or mulch around the stems of the potato blight meaning the pathogen has farther to travel to get to the tuber. Another approach is to destroy the canopy around five weeks before harvest, using a contact herbicide or sulfuric acid to burn off the foliage. Eliminating infected foliage reduces the likelihood of tuber infection.

Late blight

The blight initially presents as dark or light brown spots or lesions on leaves. The leaves typically turn brown or straw color, then fall off. The stems develop dark brown or black lesions. The disease is often fatal to young plants. The spores remain viable for five years in fallen boxwood leaves and are dispersed by wind and rain over short distances. Since they are sticky the spores may also be spread by birds, animals, and contaminated clothing and footwear. The most common mode of transmitting the blight is by the introduction of asymptomatic plants, or plants treated with fungicide (which can mask the disease) to unaffected areas. Warm and humid conditions facilitate its spread. The fungus does not need a wound to infect a plant, but it does require high humidity or free water.

Stay away from box and pachysandra plants when they are wet. Clean off the soles of your shoes before moving from one part of the garden to another. Disinfect your pruners between plants. Destroy or dispose of boxwood clippings. Avoid planting boxwoods in partly shaded areas.

There is no known cure. Fungicides may prevent the spread of the disease. To be effective, they must be applied to the entire plant, leaves and stems, which can be difficult because boxwood leaves are very closely spaced.

Boxwood blight

Usually the first sign of thrip damage is faded or dirty looking leaves. The leaves will start by turning white or grayish in color, then eventually brown as the damaged areas start to die.
Though it’s possible for thrips to kill a houseplant, it’s rare. Mature, healthy houseplants can handle a pretty heavy infestation. The biggest threat is to small or weak houseplants.
However, not only is a thrip infestation gross, they make your indoor plants look terrible, and heavy damage can stunt their growth. Other common symptoms include:
- Brown stripes on the leaves
- Faded, splotchy, pale-colored leaves
- Parts of the leaves are dying
- Flower buds are malformed, dropping, or won’t open
- Leaves start dropping unexpectedly
- New growth is deformed

Thrips can be difficult to get rid of. So, once you finally win the battle, you want to prevent them from ever coming back!
The good news is that there are a few easy ways to prevent thrips from infesting your houseplants…
- Monitor them on a regular basis for the first signs of an infestation
- Debug all of your plants before bringing them back inside for the winter
- Keep anything that you bring in from your garden (cut flowers, veggies…etc) far away from your houseplants
- Inspect all new houseplants before bringing them home, then quarantine them for a few weeks afterward

Limpleaf Fern

(Microlepia Speluncae)

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