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.

Signs of damage

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.

How to prevent

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.

Treat

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Late blight

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

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 of infected plants are premature yellowing, dieback, wilting of older leaves, and stunting of plants, followed by death of all foliage and sometimes root rot. Unlike Botrytis species, S. cepivorum does not produce spores to spread and establish disease.

The hyperparasite Coniothyrium minitans may provide biological control, and a commercialized product ‘Contans’ is based on this.

Certain crops such as lettuce, beans and chicory can contribute to inoculum build-up significantly. Soil infestations can also be reduced by metam sodium and biological soil disinfestation.

Sclerotiniaceae

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

Calcium deficiency symptoms appear initially as localized tissue necrosis leading to stunted plant growth, necrotic leaf margins on young leaves or curling of the leaves, and eventual death of terminal buds and root tips. Generally, the new growth and rapidly growing tissues of the plant are affected first. The mature leaves are rarely if ever affected because calcium accumulates to high concentrations in older leaves. Calcium deficiencies in plants are associated with reduced height, fewer nodes, and less leaf area.

Preventative measures, such as irrigating prior to especially high temperatures and stable irrigation will minimize the occurrence.

Calcium deficiency can sometimes be rectified by adding agricultural lime to acid soils, aiming at a pH of 6.5, unless the subject plants specifically prefer acidic soil. Organic matter should be added to the soil to improve its moisture-retaining capacity. However, because of the nature of the disorder (i.e. poor transport of calcium to low transpiring tissues), the problem cannot generally be cured by the addition of calcium to the roots. In some species, the problem can be reduced by prophylactic spraying with calcium chloride of tissues at risk. Plant damage is difficult to reverse, so corrective action should be taken immediately, supplemental applications of calcium nitrate at 200 ppm nitrogen, for example. Soil pH should be tested, and corrected if needed, because calcium deficiency is often associated with low pH.

Blossom end rot

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

A diagnostic feature of this disease is the presence of many dark-brown, pimple-like structures called pycnidia (fruiting bodies of the fungus) that are readily visible in the tan centers of the spots. When spots are numerous, affected leaves turn yellow and eventually shrivel up, brown, and drop off.

Use disease-free seed. There's no evidence that this fungus is carried by seeds, but err on the safe side and don't save seed from infected plants. Thoroughly processing the tomato seeds you are saving will also help rid the seeds of lingering diseases.
Start with a clean garden. Dispose of all affected plants. The fungus can over-winter on the debris of diseased plants. It's important to dispose of all the affected plants far away from the garden and the compost pile. Keep in mind that it may have spread to your potatoes and eggplants, too.
Avoid overhead watering. Water aids the spread of Septoria leaf spot. Keep it off the leaves as much as possible by watering at the base of the plant only. Of course, it's impossible to keep the rain off your plants, but every little bit helps.
Provide room for air circulation. Leave some space between your tomato plants so there is good airflow. Stake them so that they are not touching the ground and not all bunched together. Good air circulation is especially important during damp and rainy periods.
Mulch below the plants. A layer of mulch will help prevent spores on the ground from splashing up onto the lower leaves.
Plant next year's tomatoes in a different section of your garden. In small gardens, it's not always practical to rotate your crops, so good clean up and sanitation become even more important.

Removing infected leaves. Remove infected leaves immediately, and be sure to wash your hands and pruners thoroughly before working with uninfected plants.
Consider organic fungicide options. Fungicides containing either copper or potassium bicarbonate will help prevent the spreading of the disease. Begin spraying as soon as the first symptoms appear and follow the label directions for continued management.
Consider chemical fungicides. While chemical options are not ideal, they may be the only option for controlling advanced infections. One of the least toxic and most effective is chlorothalonil (sold under the names Fungonil and Daconil).

Septoria leaf spot

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

Initially spots of limited size, slightly concave, appear at the peduncular scar of some fruits, or near growth cracks or various wounds. They gradually spread with a fairly typical dark brown to black colour. The lesions decay further while their perimeter is clearly identified. They eventually cover a large proportion of ripe or unripe fruits if the environmental conditions are favourable. Whatever their development stage, the fruits undergo internal rot extending to the seeds. Brown to black globular structures, pycnidia, can be observed in the damaged tissues. They are spherical and irregularly shaped, ostiolate, and contain many hyaline and unicellular conidia, containing two lipid droplets.

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.

Dothideomycetes

Phyllosticta causes circular leaf spots with brown/reddish borders. The spots can be really large covering a large area of the leaf. Initial symptoms include small watersoaked regions on the leaves. lesions become more apparent with a ring-like pattern at alter stages.

Repeated applications of fungicides such as Dithane M45, Captan, Ferbam, Mancozeb or thiophanate-methylbased treatments will help control infection levels and can prevent new infections in healthy plants, but it is difficult if not impossible to completely eradicate the fungus in an infected host plant.

Remove and dispose of affected leaves from infected plants to keep the fungal spores from spreading into the growing environment. Some growers have reported covering the mature lesions with clear nail polish to prevent the dissemination of spores.

Phyllosticta leaf spots

Mealybugs damage crops in a variety of ways. Pupae and females drink the sap of the plant, slowing growth and causing deformation and yellowing of the leaves, sometimes with subsequent leaf fall. The overall effect is a weakening of photosynthesis and hence a decrease in yield.

To keep mealybugs at bay, spray your plants once a week with a solution of neem oil in water. If you coat all plant surfaces, the neem oil will slow or stop feeding on your plants by a wide variety of pests. In addition, the oil coats any eggs or crawlers and will smother them.

Pyrethroids such as permethrin, bifenthrin or cyfluthrin can be used to control mealybugs. Some gardeners use Green Lacewing (Chrysopidae) larvae to control mealybug infestations, as the larval Lacewings are voracious predators of aphids and other small insects.

Pseudococcidae

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

As a general rule, common symptoms of a bad root knot nematode infestation can include chlorosis (yellowing of the leaves/stems), stunted growth, wilting, and a lack of production of fruit.
However, these may be nonexistent to severe depending on the population of nematodes, the health of the plant, the natural resistance of the plant, and any number of other factors in the soil makeup. It can also be hard to separate the symptoms from other pest/disease issues.
The only real way to be sure that it is in fact root knot nematodes is to carefully remove a plant from the soil and examine its roots. If there are a lot of galls growing along the root system, it’s likely root knot nematodes at work.
While these microscopic nematode parasites can be problematic, root knot nematodes are not uncontrollable. They may be tricky, but with good garden management, you won’t have negative consequences!

Prevention is always the best cure for a pest problem, and root knot nematodes are no exception. So let’s talk about prevention.
First off, plant nematode-resistant varieties. There are a wide variety of different seed suppliers who carry nematode-resistant seed stock, usually notated as an N in the resistance charts.
If you cannot plant nematode-resistant strains, practice good crop rotation. Some species of root knot nematodes are more selective than others. Planting cover crops like marigolds or sudangrass between at-risk crops will also bring down the nematode population.
Remove the roots of old plants when clearing the bed. As root knot nematode juveniles can live in the galls they form on the roots, they will continue to multiply even as the roots are dying out. Removing the remaining root mass can extract those juveniles.
Till the soil 2-3 times in the fall. This breaks up the soil, turning the nematodes up to the surface where they will die off from exposure to the sunlight. This will impact both beneficial and parasitic nematodes, so you may need to re-add beneficial nematodes again in the spring.
Plant overwintering grass cover crops like wheatgrass, ryegrass, or rye. Sudangrass is also good and offers some nematicide properties. Keep these mowed down to a manageable level, and till them under in the spring to add more plant matter to the soil.
Regularly add more organic material to your soil. Adding more composted leaves, grass clippings, and manure to your beds will help naturally control the population of nematodes in the soil, since nematodes prefer living material to decaying plant matter.

There are two organic nematicide variants available: ones based on geraniol (the oil of geraniums), and ones based on quillaja saponaria, the soap bark root. Remember, though, that nematicides will kill off both beneficial and parasitic nematodes.
Quillaja saponaria compounds such as Monterey Nematode Control use the saponins from the soap bark tree to help reduce nematode populations.
You can also use an azdirachtin product such as AzaMax, which is a pure azdirachtin extracted from neem oil. This may work as a light nematicide, but tends to be better against other pests such as spider mites, thrips, aphids, and more.
Add neem seed meal, crab meal, or oyster shell flour to your soil. All three are fertilizers, but they’re great soil builders in the war against root knot nematodes.
Neem seed meal is a gentle fertilizer which is made from the leftover material after making neem oil. It helps reduce a number of pests naturally, plus it breaks down to add low levels of nitrogen to the soil. It also can help strengthen the roots of plants to make them resistant.
Crab meal encourages beneficial soil microorganisms which reduce nematode population. It also helps plants to increase the strength of their cell walls, making them more naturally resistant to many conditions.
Oyster shell flour is in essence a form of diatomaceous earth. While it has less effect when it’s wet, it can help make the soil less hospitable to nematode populations and reduce other pests as well.
Black walnut leaves and hulls have a natural compound in them which is called juglone. This compound is an extremely effective killer of root knot nematodes, but can have an adverse effect on some plants. That’s why there’s few weeds around walnut trees!
If you want to put an organic source of juglone to work in your garden, use fresh walnut leaves or smashed hulls as a thick layer of compost on your bed, or just build a tall pile there. Regularly turn it to keep it composting. I use leaves, as they’re quick to break down.
The juglone compounds will seep into the soil when you wet down the pile, and after three to six months should have broken down enough that they will no longer be toxic to other plants. This also helps wipe out weeds or other pests that may be in your beds during composting.

Root-knot Nematodes

Symptoms of bacterial infection in plants are much like the symptoms in fungal plant disease. They include leaf spots, blights, wilts, scabs, cankers and soft rots of roots, storage organs and fruit, and overgrowth. Bacterial spots: the most common symptom of bacterial disease is leaf spots.

The best way to prevent fungi from attacking your plants is to buy disease resistant varieties whenever possible. Other ways include minimizing the amount of water contacting foliage. Water at the soil level and early in the day. This allows foliage to dry out quickly, should it become wet.

Antibiotics: streptomycin and/or oxytetracycline may also help kill or suppress plant pathogenic bacteria prior to infection and reduce spread of the disease, but they will not cure plants that are already diseased. Antibiotics are also used to treat diseases caused by fastidious vascular bacteria.

Bacteria

Tan to brown leaf spots, small black fruiting bodies (pycnidia) may be visible in the lesions. Lesions on Rudbeckia and Echinacea are purple. Lesions may be more severe on older foliage.

Avoid overhead irrigation or carefully time it such that the duration of leaf wetness is minimized.

Protectant fungicides can be used to manage Septoria leaf spot.

Mycosphaerellaceae

- Black or dark brown, superficial fungal growth on the aerial parts of plants, particularly the upper leaf surfaces
- The amount of growth can vary from a fine soot-like or powdery deposit, to a thick sheet of growth that may crack or peel away from the leaf surface during dry conditions
- The growth can sometimes be washed away, leaving a healthy-looking leaf surface beneath
- Sap-sucking pests such as aphids, scale insects, mealybugs or whiteflies can often be found on the plant, above the point where the sooty mould is growing
- In some cases these insects may occur on plants that overhang those affected with sooty mould
- Ants may also be seen in association with the sap-sucking pests
- Leaves, stems, fruit, etc. where the sooty moulds are growing are contaminated with sticky honeydew

It isn’t really possible to preventively treat against sooty mold, and when it appears it is immediately recognizable.
There are a few things to do that can reduce the likeliness that this disease would appear.
- Ensure your plant has sufficient nutrients and is well watered. A plant weakened by poor soil or lack of water is a vulnerable plant.
- Increase the diversity of plants and flowers in your garden, it is the best way to protect them naturally from their predators.

Sooty mold grows on the honeydew dropped by many sap-feeding insects (most commonly aphids, scale and whiteflies). The honeydew is a sugary liquid that the insects excrete as waste. Sooty mold in itself does not feed on plant tissues or cause damage, but it can block enough sunlight to affect photosynthesis which can weaken the plant over time. It is also very ugly and difficult remove (more on that in a bit).
The first step is to identify and treat the insect causing the problem:
- Soft or armored scale (look like small turtle shells affixed to the stems and/or leaves, sometimes very well-camouflaged in color or texture. Egg sacs are often wispy and white),
- Aphids (small green, yellow or tan insects with thin legs & antennae, wooly aphids look a bit like tiny sheep)
- Whitefly (tiny, white-winged flies).
A population of insects large enough to cause a sooty mold problem is usually pretty easy to spot and identify. Controlling the insects will stop the rain of sugar water that feeds the sooty mold.
The mold itself is difficult to remove, but you can hasten the rate at which it naturally weathers off. Spraying the leaves with insecticidal soap can help soften the sooty coating. Spray late in the day so the soap remains moist for as long as possible. If you can spray a few hours before a heavy rain is forecast the rain will be better able to remove the sooty mold.
If the plant has a rugged leaf, like holly or gardenia, you can follow the soap application with a strong jet of water from your garden hose after you’ve given the soap a little time to soften the mold. Be careful with softer-leafed plants and new growth, as a strong water stream can tear or bruise leaves. You’ll probably have to repeat the process a few times to wear the coating of sooty mold off over time.
If your insect eradication was successful, you’ll see that new growth on the sooty mold affected plants will remain fresh and clean. The mold does not spread without the honeydew to grow on, so new sooty mold indicates a continuing insect problem.

Sooty Mold

Lower leaves are yellow. Plant looks wilted Roots will be rotting or stunted. No new growth. Young leaves will turn brown. Soil will appear green (which is algae)

Rainwater harvesting and recycled wastewater also allow to reduce scarcity and ease pressures on groundwater and other natural water bodies. Groundwater recharge, that allows water moving from surface water to groundwater, is a well-known process to prevent water scarcity.

The provision of water treatment chemicals ensures the provision of safe water.

Water-related issue

Wilting. This is the classic sign of an under watered plant. Too little water causes a plant to lose turgor, the rigidity in cells and tissues. There are some diseases that can trigger wilting, but the easiest and most likely explanation is under watering. Dry soil. If the soil around a plant is dry, it may need more water. Exceptions to this are some succulents, like cacti, which don’t need much water because they can store it so well. Dry, dead leaf tips. When a plant doesn’t get enough water, the tips and edges of leaves dry out and turn brown. Ultimately, entire leaves will brown and die. Slow growth. If you are chronically under watering a plant, but still giving it enough water to survive, growth will be slower than normal or expected. New growth, such as leaves, may be small. Visible footprints. For a sign that turf grass is not getting adequate water, look to your footprints. After you step on the grass, it should bounce back quickly. If the footprints remain visible for several minutes, the grass is too dry.

Mulch plants with a 3-to-4-inch layer of organic mulch (woodchips, shredded bark) to reduce soil evaporation and temperature fluctuations, and to conserve moisture. Irrigate slowly so water percolates down into the soil. Do not fertilize unless adequate irrigation is available.

Most garden plants, flowers, and shrubs do best when they receive at least 1 inch of water per week, although they may need more during hot, dry spells. Rain isn't always sufficient at supplying enough water for plants to thrive, so don't count on it to keep plants healthy.

Water deficiency

The black spots are circular with a perforated edge, and reach a diameter of 14 mm (1⁄2 inch). Badly affected plants, however, will not show the circular patterning, as they combine to cause a large, black mass. The common treatment of the disease is to remove the affected leaves and spray with antifungal solutions. Some stems of the roses may become affected if untreated, and will cause progressive weakening of the rose.

Keep the foliage as dry as possible, since the spores need a wet surface in order to germinate. Avoid overhead watering, or water early in the day so the foliage has time to dry before nightfall. Improve the air circulation around your roses by spacing them properly and pruning them regularly.

Removing infected leaves from the plant and fallen leaves from the ground will slow the spread of the infection, as does avoiding wetting the leaves of plants during watering. An infected plant can be removed from the area, which will slow the spread of infection to other plants, but this often is not desirable. Fungicides, such as mancozeb, chlorothalonil, flutriafol, penconazole, or a copper-based product, applied upon new leaf emergence or first appearance of black spot, can be used to control the disease. If a more natural and nontoxic approach is desired, diluted neem oil is effective both against black spot and as an insecticide against aphids, or cows milk diluted 1:3 with water is effective if sprayed on to the leaves. It is usually necessary to repeat the spraying at seven- to 10-day intervals throughout the warmest part of the growing season, as the fungus is most active at temperatures from 24 to 32 °C (75 to 90 °F).

Black spot

There are many symptoms of aphid damage, including decreased growth rates, mottled leaves, yellowing, stunted growth, curled leaves, browning, wilting, low yields and, eventually, death. Along with the loss of plant juices from direct feeding, aphids can spread diseases.

1. Monitor your plants. Beginning early in the season, check your plants frequently for the presence of aphids, paying close attention to plants you've found aphids on before. 
2. Check for ants. 
3. Plant onions. 
4. Don't over fertilize your plants.

Despite the fact that herbal infusions and decoctions are not chemicals, it should not be overlooked that they: in high concentration can cause burns in plants; can be dangerous not only for aphids, but also for other insects; at least some of them are poisonous to humans. Therefore, it is necessary to use such drugs wisely, observing safety measures, recipes and rules for use. Before the first use, any solutions must first be checked in a limited area, and only then, having made sure of the effectiveness of the product, apply throughout the entire area. Fruit crops can be processed with decoctions and infusions during the budding period, immediately after flowering and no later than 14-40 days before harvesting. It is recommended to process berry crops with infusions before flowering and after the berries are harvested. Vegetable crops can be sprayed with herbal infusions for the last time no later than a month before the fruit is removed.

Sternorrhyncha

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

Whiteflies tend to prefer to feed on new growth, so check around any newly unfurled leaves first.
Check the undersides of leaves—especially around the veins—for white insects, even if they aren’t immediately visible, and feel leaf surfaces for sticky honeydew. If the whiteflies are feeding, they’ll suddenly all fly off the leaves in a swarm, so it’s very obvious.
You may also find eggs laid on the undersides of leaves. This is the beginning of a new generation! When the eggs hatch, the larvae will look like teeny white ovals without legs; they don’t move but they immediately start sucking the plant juice. This is why gardeners often miss whiteflies until it’s too late. Adult females can produce up to 400 eggs, which hatch in about one week to a month after laying. They are usually laid in a circular pattern. Eggs are pale yellow when newly laid and brown when about to hatch.

1 Your first line of defense should be inspecting all plants for pests before you bring them home, as well as keeping any new additions away from the rest of your plants for a period of time. This will allow you to identify and curtail any pest or disease issues that appear.
2 Keeping natural predators around will prevent whiteflies from ever exploding in population. For this reason, avoid using insecticides. Ladybugs, spiders, green lacewing larvae, and dragonflies are a few of many beneficial insects that can control a whitefly population. Hummingbirds are another natural predator. Try creating a habitat that will attract dragonflies and damselflies (which also helpfully eat mosquitoes) or beautiful hummingbirds.
3 When it comes to whiteflies, avoid chemical insecticides; they’re usually resistant and all you end up doing is killing the beneficial insects—their natural predators—and the insects that pollinate the garden for a better harvest!
4 Mulch early in the season with aluminum reflective mulch, especially around tomatoes and peppers. The reflective mulch makes it challenging for whiteflies to find their preferred host plants. 
5 Set out yellow index cards coated with petroleum jelly to monitor whiteflies, especially when it comes to tomatoes, peppers, sweet potatoes, or cabbage crops. A half-and-half mixture of petroleum jelly and dish soap, spread over small boards painted bright yellow, is sticky enough to catch little whiteflies, too. To whiteflies, the color yellow looks like a mass of new foliage. The bugs are attracted to the cards, get stuck in the jelly, and die.

To control whiteflies, there are various solutions and traps that you can use. The biggest tip is: start early! In the mornings and evenings, as you wander the garden or tend to your houseplants, check the back of the leaves for eggs or notice when little bugs “fly away” as you approach your plants.
- Always start with blasting whiteflies (as with aphids and many other insect pests) with your watering hose or a spray bottle. This will cause them to scatter and will dislodge nymphs and eggs to some extent.
- Consider spraying your plants’ leaves with an insecticidal soap, following the directions on the packaging. Be sure to spray the undersides of leaves, too. Follow up 2 or 3 times, as necessary. 
Spray plants in the evening when temperatures are cooler, as mid-day heat may cause an adverse reaction in your plant. Plus, spraying in the evening allows you to avoid accidentally spraying any pollinators or beneficial insects.
- According to the National Gardening Association, the following simple homemade mixture should be helpful to control and deter whiteflies: Use a mix of dish soap and water. A good squirt of soap to a gallon of water should work. As mentioned above, only spray in cooler temperatures; late in the day is best. The NGA mixture is a pretty benign combination, and whiteflies are nearly impossible to get rid of, so it’s best to try more preventative tactics first, as mentioned below.
- If all else fails and your whitefly population is persistent, you can (carefully) use a handheld vacuum every few days to remove them from your plants. This gets rid of both nymphs and adults. Just be sure NOT to empty your vacuum into a trash can inside your home afterward

Whiteflies

A range of lesions can occur including concentric oblong light oval-shaped rings (early sign), light green diamond-shaped areas, concentric green and tan oval-shaped rings, tan necrotic spots, and green islands within tan necrotic spots. Damage can reduce harvest yield and grade of onions.

Reduced bulb size and quality of symptoms develop while bulbs are still growing. Control thrips. Control weeds and volunteer onion plants. Remove and destroy infected plants.

Monitor thrips populations with sticky traps starting in June. Damage is often first noticed at field edges, in areas of stressed plants, or in locations with thin plant stands. Infected plants may not show symptoms for several weeks. Sometimes symptoms may never appear. Reduced bulb size and quality of symptoms develop while bulbs are still growing. Control thrips. Control weeds and volunteer onion plants. Remove and destroy infected plants. Rotate crops.

Iris yellow spot virus

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

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

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

Common, Persian, Chinese, and Japanese lilac leaves develop round to irregularly shaped brown spots with yellow halos. These spots enlarge and blight entire leaves. Succulent twigs are girdled, killed, and turn black.

1. Exclusion or eradication of the pathogen (quarantine and use of pathogen-tested seeds and propagated materials)
2. Use of clean transplants.
3. Monitor crops regularly and use predictive models.
4. Reduce the pathogen levels by crop rotation.
5. Remove weeds and incorporate crop residues that can host the disease.

The most common strategy for controlling diseases caused by Pseudomonas syringae is, as it has been for more than 5 decades, to spray bactericides. These mainly include a variety of copper compounds or other heavy metals, with or without various combinations of fungicides or other pest-control chemicals.

Pseudomonas

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

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

Plants with severe rust infection may appear stunted, chlorotic (yellowed), or may display signs of infection such as rust fruiting bodies. Rust fungi grow intracellularly, and make spore-producing fruiting bodies within or, more often, on the surfaces of affected plant parts.

Pick off and destroy infected leaves and frequently rake under plants to remove all fallen debris. Water in the early morning hours — avoiding overhead sprinklers — to give plants time to dry out during the day.

Select rust-resistant plant varieties when available.

Pucciniaceae

Loss of chlorophyll, with the resulting yellowing of the leaves is the most obvious sign of senescence and in some cases, as seen in Figure 1a and c, the additional synthesis of anthocyanins during senescence results in dramatic orange, red and even purple coloration.

Leaf senescence occurs when the leaf is no longer of use to the plant. It is a normal aging process.

Senescence

Rust diseases come in different varieties and can affect a wide range of plants. People often struggle with rust on their roses. It is easy to remember the defining characteristics of this fungus, as they match its name. Rust plant disease will look similar to the rust that appears on that old bicycle in the shed.
- Look for yellow or white spots forming on the upper leaves of a plant.
- Look for reddish to orange blister-like swellings called pustules on the undersides of leaves.
- Orange or yellow spots or streaks appear on the undersides of the leaves.
- Within these spots that form are spores.
- Usually leaf distortion and defoliation occur.

- Dust your plants with sulfur early in the season to prevent infection or to keep mild infections from spreading.
- Space your plants properly to encourage good air circulation.
- Avoid wetting the leaves when watering plants.
- There are many effective rust fungicides you can try.

1 Select rust-resistant plant varieties when available.
2 Pick off and destroy infected leaves and frequently rake under plants to remove all fallen debris.
3 Water in the early morning hours — avoiding overhead sprinklers — to give plants time to dry out during the day. Drip irrigation and soaker hoses can be used to help keep leaves dry.
4 Use a slow-release, organic fertilizer on crops and avoid excess nitrogen. Soft, leafy, new growth is most susceptible.
5 Apply copper sprays or sulfur powders to prevent infection of susceptible plants. For best results, apply early or at first sign of disease. Spray all plant parts thoroughly and repeat every 7-10 days up to the day of harvest.
6 Effectively treat fungal diseases with SERENADE Garden. This broad spectrum bio-fungicide uses a patented strain of Bacillus subtilis and is approved for organic gardening. Best of all, it’s safe to use — you can treat and pick crops the same day!
7 Containing sulfur and pyrethrins, Bonide® Orchard Spray is a safe, one-hit concentrate for insect attacks and fungal problems. For best results, apply as a protective spray (2.5 oz/ gallon) early in the season. If disease, insects or wet weather are present, mix 5 oz in one gallon of water. Thoroughly spray all parts of the plant, especially new shoots.
8 Prune or stake plants and remove weeds to improve air circulation. Make sure to disinfect your pruning tools (one part bleach to 4 parts water) after each cut.
9 Use a thick layer of mulch or organic compost to cover the soil after you have raked and cleaned it well. Mulch will prevent the disease spores from splashing back up onto the leaves. Burn or bag infected plants after the growing season . Do NOT compost.

Leaf Rust

Brown, yellow, gray, or straw-colored needles at tip of current season's growth; needles usually stunted and shoot may curl. Branch dieback. Small, black fruiting bodies on needles, cones, or shoot tissue. Cankers on stems or branches. Oozing resin that adheres to blighted needles.

Preventing the initial infection is a better strategy than attempting to cure a diseased tree. The first line of defense in preventing disease is planting disease free stock, planting in a disease free area, and selecting a disease resistant species. Beyond the selection of clean, resistant stock and planting location, trees that have proper water and nutrient management are healthier and less susceptible to Diplodia tip blight. Controlling wood boring insects that create wounds for Diplodia to exploit, is another cultural practice that can prevent disease. Poor airflow and high humidity are conditions that favor disease development; keeping grass and weeds trimmed down at the base of the tree allows for better airflow and can limit disease development. Once a tree is diseased, the goal is to limit the amount of inoculum present. The blighted needles and cones will have the pycnidia survival structures that contain thousands of spores. Remove debris from the base of the tree and destroy. During dry weather (not during Spring or early Summer), cut away infected shoots, cones, and branches. Sanitary techniques like sanitizing pruning tools between each cut will prevent further spread of the disease.

When disease pressure is high, chemical controls is advised. First, spray should occur early spring at candle elongation. Repeated sprays should occur every two weeks until needles reach full size. Fungicides containing the following active ingredients have been shown to be efficacious: chlorothalonil, methyl, thiophanate-methyl, mancozeb, and copper hydroxide with mancozeb. Always read and follow the label.

Sphaeropsis blight

The leaves become narrower and longer, and with severe damage, the plants become chlorotic and die.

There is no cure for nectria canker, so it is important to take steps to prevent it affecting young and vulnerable trees. Pruning injuries can be a major source of infection, so avoid pruning trees in the fall, especially in wet conditions. Restrict pruning to dry weather and remove any branches or stems that have been infected with the fungus.

Freezing damage is another important way in which trees get infected. For young transplants, providing protection from freezing can prevent the disease. Avoid other types of injury and keep your trees healthy to minimize the risks from nectria infection. This means being careful with the lawnmower around trees, preventing or managing pests, and providing adequate water and nutrients.

Nectriaceae

General symptoms can include one or more of the following symptoms: curling or cupped leaves, stunted growth, discolored leaves, or leaves with dead spots. The same herbicide may cause different symptoms on different plant species. Since herbicides do not leave a "calling card" like mites, insects, and diseases (but the damage they cause can be mistaken for herbicide damage), it is advised to rule these out first. Other disorders that produce symptoms that can resemble herbicide damage include virus diseases, adverse weather, salt damage, drought, soil compaction, misapplied fertilizers, root stress, and nutrient deficiencies. Excluding these as causes requires close examination of the site and attention to patterns. Is the pattern of damaged plants consistent with drifting spray? Is more than just one kind of plant affected? Did the symptoms appear within one or two days (in most cases) of the suspected application of an herbicide? Were any lawn weed control products used in the area, including weed and feed products containing an herbicide? The answer to these and other questions can help make a circumstantial case of herbicide damage.

Use shielded booms to minimize herbicide off-target movement. Use spray additives within label guidelines to reduce production of small spray droplets. This will result in less potential for drift. Avoid tank mix ammonium sulfate with volatile herbicides as ammonium sulfate increases volatility.

Organic strategies that help plants recover from herbicide damage are those that aid in maintaining plant vigor:  water during dry periods; fertilize with organic fertilizer according to a soil test report; and watch for and control any insect or disease problems using organic approaches.

Herbicide damage

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

Uneven swelling and maturation of the drupe, as well as premature staining without enlargement.

Neem oil as a preventative or light-infection treatment. Copper fungicides or phosphorus acid fungicides can treat larger scale infections. Prevention is the best cure.

Planting resistant cultivars. Treating with hot water on Roses cuttings can be effective, the water must be 44 degrees and treated for 15 minutes.

Peronosporaceae

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

The pathogen causes angular chlorotic lesions on the foliage. These lesions appear angular because they are bound by leaf veins. During humid conditions, inspection of the underside of the leaf reveals gray-brown to purplish-black fungal growth. This downy material is the sporulation of the pathogen. Magnification of the sporulation reveals the acutely and dichotomously branched sporangiophores bearing lemon-shaped sporangia. Eventually, leaves will turn necrotic and curl upwards. The disease is sometimes called wildfire because of how rapidly it progresses, as if the crop were burned by fire. Symptoms on watermelon and cantaloupe are different from on other cucurbits; leaf spots are typically not angular and turn brown to black in color. Often, an exaggerated upward leaf-curling will occur. Regardless of which cucurbit is involved, only the leaves are infected, not fruit, flowers, stems or roots. Disease of the leaves results in three major effects: 1. reduced yields, 2. a greater proportion of misshapen fruit, especially in cucumber, and 3. sunscalded fruit, due to increased exposure to direct sunlight, especially in watermelon and winter squash.

Early detection of downy mildew and immediate or preventative fungicide application is imperative for the control of this disease. A forecasting system exists to assist growers in timing their fungicide applications for maximum benefit. The system tracks outbreaks of the disease and provides a forecast or risk assessment for future outbreaks.

Resistant cultivars - Host resistance is an important tool in disease control and should be used whenever possible. Cultivars resistant to downy mildew have been developed for cucumber and cantaloupe and to a lesser extent for squash and pumpkin. Although cucumber downy mildew has been severe on resistant cultivars, these cultivars are more effective than susceptible cultivars in delaying infection. Chemical control - Chemical control is highly recommended because downy mildew is an aggressive and destructive disease and satisfactory control without the use of fungicides is unlikely. Both protectant and systemic products should be applied. Fungicides are most effective when applied prior to infection and reapplied at 5- to 7-day intervals. The following products have proven to be the most effective fungicides in cucumber downy mildew control in North Carolina trials conducted annually from 2004 to 2008: Presidio (fluopicolide, Valent), Ranman (cyazofamid, FMC), Previcur Flex (propamocarb, Bayer), Curzate (cymoxanil, DuPont), Tanos (famoxadone and cymoxanil, DuPont), and Gavel (zoxamide and mancozeb, Dow AgroSciences). These products should be applied in a program to prevent pathogen resistance, that is, rotated with fungicides of a different mode of action. Protectant fungicides such as chlorothalonil and mancozeb should be used as mixing partners. Вiological control - Although many biological control products have been evaluated for their ability to control downy mildew, none have proven effective and are not recommended for use.

Cucurbit downy mildew

The chlorophyll content of the plant leaves is reduced which results in pale yellow color (chlorosis). Older leaves turn completely yellow. Flowering, fruitings, protein and starch contents are reduced. Reduction in protein results in stunted growth and dormant lateral buds.

Nitrogen deficiency can be prevented in the short term by using grass mowings as a mulch, or foliar feeding with manure, and in the longer term by building up levels of organic matter in the soil.

Fertilizers like ammonium phosphate, calcium ammonium nitrate, urea can be supplied. Foliar spray of urea can be a quick method.

Nitrogen 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

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

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

If the stem is mushy or brittle, check the roots for the same conditions. The roots, too, should be pliable but firm. If both the stems and roots are brittle or mushy, the plant is dead and you will simply need to start over.

Repot your plant. Use a high-quality indoor plant potting mix to revitalise your plant, and choose a pot that's wider than the last one. ... Trim your plant. If there's damage to the roots, trim back the leaves. Move your plant.  Water your plant.  Feed your plant.  Wipe your plant.

Gently remove the plant from its container. If you see more roots than soil, or roots coiling around the inside of the pot, it is time for a bigger container. Over time, most plants outgrow their pots. Sometimes, all it takes to revive a dying plant is a little repotting.

Dead plant

Symptoms of Cercospora leaf spot first appear as individual, circular spots that are tan to light brown with reddish purple borders. As the disease progresses, individual spots coalesce. Heavily infected leaves first become yellow and eventually turn brown and necrotic.

Avoid overwatering or watering in the late evening to reduce free moisture. Avoid overhead watering where the water can dislodge and disperse spores to uninfected plants. Space plants to encourage air movement and reduce high humidity levels.

For the most part, treating Cercospora leaf spot means preventing the fungi from infecting your plants in the first place.

Cercospora leaf spot

Symptoms first appear as a slight yellowing of foliage and wilting of upper leaves. As wilting progresses, leaves may turn dull-green to brown and remain attached to the plant. When the stem and roots are cut diagonally, reddish-brown streaks are visible in the vascular tissues.
Signs and symptoms:
- Initially, plants wilt during the hottest part of the day and recover at night.
- Leaflets turn yellow on one side of the plant, or even just leaflets on one half of a compound leaf.
- The entire plant soon turns yellow and wilts. Browning of leaves occurs rarely.
- Peel the epidermis off the lower stem to see dark red and brown discolored vascular tissue.

Fusarium is most prevalent in warm soils. It is harbored in old plant debris and soil. The best way to prevent infection in your crops or plants is rotation and sterilization. 
Never plant the same crop in the same place annually. 
Pots should be sterilized with a bleach solution and new soil used when reusing them. You can also solarize beds, by spreading black plastic over an area in full sun for a month to kill the fungus. This causes extreme high temperatures that will “cook” the fungus and provide good control of Fusarium. 
Wash off tillage equipment, shoes and other tools that might have encountered infected soil. Remove all old plant debris annually and if you think it might be contaminated, burn it. Do not compost contaminated material as this provides an ideal incubation condition for propagating the fungus.

1 Plant resistant varieties when available.
2 Remove stricken growth from the garden and sterilize pruning clippers (one part bleach to 4 parts water) between cuts.
3 Use fumigants to control many garden insects, like cucumber beetles, which are known to spread the disease.
4 High nitrogen fertilizers may increase susceptibility to the disease. Test your soil and use a slow-release, organic fertilizer in the vegetable garden.
5 Hand pull or spot treat weeds using a weed flamer or natural herbicide — many weed species host the disease pathogen.
6 Mycostop is a biological fungicide that will safely protect crops against wilt caused by Fusarium. Approved for use in organic crop production, it can be applied as a soil spray or drench (1-2 gm/ 100 sq ft) to seedlings, ornamentals and vegetables. Apply sufficient water during application to move Mycostop into the root zone.
7 If the disease persists, it is best to remove the entire plant and solarize the soil before planting again.
To solarize the soil, you must leave a clear plastic tarp on the soil surface for 4-6 weeks during the hottest part of the year. Soil solarization will reduce or eliminate many soil inhabiting pests including nematodes, fungi, insects, weeds and weed seeds.

Fusarium Wilt

Mosaic symptoms are variable but commonly include irregular leaf mottling (light and dark green or yellow patches or streaks). Leaves are commonly stunted, curled, or puckered; veins may be lighter than normal or banded with dark green or yellow.

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

Control measures are the use of resistant varieties, the destruction of resistant vectors and weeds - pathogen reserves, removal of diseased plants and plant debris, crop rotation, sterilization of tools for plant care.

Mosaic virus (general)

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.

Common burdock

(Arctium minus)

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