Rust symptoms first appear on the upper and/or lower surfaces of leaves as small yellow or white slightly raised spots.

Signs of damage

Remove all infected parts and destroy them. For bramble fruits, remove and destroy all the infected plants and replant the area with resistant varieties. Clean away all debris in between plants to prevent rust from spreading. Avoid splashing water onto the leaves, as this can help spread rust.

How to prevent

Use a mild bleach solution, and rinse and dry them thoroughly before putting them away. Rake up and remove fallen or dead leaves and other plant debris. Some gardeners compost vegetation that show signs of rust, expecting the compost pile to heat up enough to kill the spores.

Treat

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Rust

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

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

Hosta virus X does not kill the plants infected, but Hostas that have been infected do show a variety of other symptoms, such as: Ink-bleed, which makes the plant look discolored in certain spots, and this effect is generally centered on a vein. An example of this is shown in the photo in this article. Desiccation or Collapsed tissue, which can be signs of heavier infection, makes the plant look as if it is dried out. Mottling, which makes the plant appear blotchy. This is not always a symptom of HVX, and could be from another virus, but it should always be treated as an infected plant regardless. A Hosta may no longer express symptoms of the virus when it grows back in the Spring, even though it may have shown symptoms in a previous year. Nonetheless, the plant should still be considered infected with HVX.

The only way to eliminate the disease is to destroy infected plants (and any associated plant debris) by burning (where allowed by local ordinance) or landfilling. DO NOT compost hostas with HVX.

Once a Hosta plant is infected, it will be infected for the rest of its life. Any plant suspected of being infected should be burned if it is legal to do so. If it is not, then it should be tossed in the garbage, but infected Hosta plants should never be composted. If any plant in a batch shows symptoms, the entire batch should be considered infected and be destroyed. Once a plant has been removed, the spot occupied by the Hosta should be left empty for a long time to prevent the spread of the virus to a plant that replaces it. The virus primarily spreads through infected sap, so cutting multiple plants with the same tool can spread the virus. Animals that eat the plants may also spread the virus through sap by eating from an infected plant and then eating from an uninfected plant.

Hosta virus x

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

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

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

The first thing you should do as soon as you spot thrips on a houseplant is to quarantine the infested plant immediately. Then check all of the surrounding houseplants for signs of thrips, and isolate any others you may find.Make sure that you begin treating the infestation right away. Also, to help prevent thrips from spreading, always wash your hands after handling an infested houseplant.
RINSE THE LEAVES
If you can, take your houseplant outside, and rinse the leaves with the hose. That will remove many of the bugs, and quickly knock down their population.You could rinse the leaves in the sink or shower instead, and that will work too. Be sure to use tepid water, and take care not to overwater your houseplant in the process.
INSECTICIDAL SOAP
Soap kills thrips on contact, and will help to give you the upper hand. You can use a pre-mixed organic insecticidal soap, or make your own using 1 tsp mild liquid soap to 1 liter of water.Be sure to spray it directly on the infested leaves to kill the bugs. Insecticidal soap doesn’t have any kind of residual effect, so it’s important to treat them often in order to completely get rid of thrips.
WASH YOUR HOUSEPLANT
You could also try washing the leaves with diluted mild liquid soap, and rinse it off with water. This will kill thrips as well, and help to quickly get the population under control.Make sure you wash the undersides of leaves too, that’s where thrips like to hide. But before washing all of the leaves, it’s best to test the soap on a few first, to make sure it doesn’t damage your houseplant.
NEEM OIL 
It’s a naturally occurring insecticide, and also has a residual effect that will help to deter future infestations.Spray a neem oil solution directly on the leaves and stems. This will kill some of the bugs on contact, and others will die when they feed on the neem oil covered leaves. Either a pre-mixed horticultural oil or a hot pepper wax spray can also be very effective to get rid of thrips on houseplants.
STICKY TRAPS 
Since adult thrips are able to fly, sticky traps can work very well to capture them. Place either yellow or blue sticky traps near the infested houseplant to attract them.

Houseplant Thrips

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

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

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

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

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

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

Botryosphaeria obtusa enters the fruit through wounds. These can be made by insects, birds or growth cracks. At first a brown spot, near the calyx, appears on the fruit. The spot on the fruit then enlarges and black/brown rings appear on the fruit. The fruit holds its shape, however, unlike other fruit diseases. The fruit will then wither up and can remain on the tree for another year before falling off. During this time pycnidia appear on the surface of the rotted fruit.

Start with clean seed. In warm, humid weather, a single infected seed in as many as 10,000 could lead to a black rot outbreak.

The most effective treatment is to prune out the infected areas on trees, to ensure transfer between trees does not occur. Fruit that is infected can stay on the tree for over a year, and therefore remaining fruit should be removed to avoid another source of inoculation for other trees. The trimmed branches or dead fruit should then be burned or disposed of immediately as the organism can survive on the dead tissue for a long period of time. Infection of leaves and fruit can be avoided by spraying them with a fungicide. The treatment for the fungicide should be also kept up to date via the manufacturer's instructions.

Black rot

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

Young seedlings develop a rot at the crown. Later, the tissue becomes soft and constricted, and the plants wilt and fall over.

Tool Sterilization. Prune Damaged Foliage. Plant Resistant Vareities. Crop Rotation. Keep The Soil From Being Soggy. But Don't Let It Get Too Dry. Sow Seeds The Right Way. Airflow Helps.

Once fusarium wilt infects a plant, there is no effective treatment. Remove and dispose of affected plants immediately; don't compost this garden refuse. Whenever possible, remove and replace fusarium-infected garden soil.

Fusarium wilts, blights, rots and damping-off

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 first sign of powdery mildew is pale yellow leaf spots. White powdery spots can form on both upper and lower leaf surfaces, and quickly expand into large blotches. The large blotches can cover entire leaf, petiole and stem surfaces. When powdery mildew infects the majority of the foliage, the plant weakens and the fruit ripens prematurely.

Control is possible with triadimefon and propiconazole. It is also possible with hexaconazole, myclobutanil, and penconazole.

Standard fungicides are an effective way to manage powdery mildew disease on plants. Spray programs of conventional fungicides are advised to begin when powdery mildew symptoms and signs are first noticed. Conventional fungicides should be applied on a regular basis for best results against the disease.

Powdery mildew

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

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

Signs of sap-sucking insect injury consist of enlarged growths or galls, leaf curling, bleaching, or yellowing of foliage. Conifers are more severely injured than hardwoods.

Use insecticidal soap, kelthane, or malathion to control the mites. Control of sucking insects with insecticides is often difficult because of the insects' capacity to reproduce rapidly. Also, they may develop resistance to the chemicals. Often a blast of water from a garden hose will knock the pests off the plant.

There are many natural enemies that help control sap-sucking insects and mites. Insecticide use can sometimes prolong infestations by killing natural enemies of these insects.

Impact of sap-sucking insects

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

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

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

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

Plants' roots are not typically visible as they are below the surface of the soil, so the symptoms of root rot are often apparent only when the disease is advanced. Roots of plants affected by root rot may turn from firm and white to black/brown and soft. Affected roots may also fall off the plant when touched. The leaves of affected plants may also wilt, become small or discolored.Affected plants may also look stunted due to poor growth, develop cankers or ooze sap. Prolonged root rot may lead to death of the plant. In extreme cases, plants affected by root rot may die within 10 days. Root rot is usually[citation needed] lethal although it is treatable. An affected plant will not normally survive, but may potentially be propagated.

To prevent recurrence and progression of root rot, it is recommended to water plants only when the soil becomes dry, and to plant the plant in a well-drained pot. It is recommended that pots used for diseased plants should be sterilized with bleach to kill potential spores. This allows the plant to drain properly and prevents fungal spores affecting the plant. It is recommended to keep the soil around the plant as dry as possible and to pry back the soil to allow proper aeration.

The most effective treatment for root rot is prevention such as destruction of affected plants. It is recommended that, in localised cases of root rot, the affected plant simply be destroyed and the surrounding soil replaced. Treatment options depend on the extent of the rot. To treat root rot, is recommended to replant the affected plant in fresh soil with good drainage to avoid standing water. It is also recommended to gently wash diseased roots and remove all brown, soft parts of the roots with a sterilized pair of scissors or a tool such as a pulaski for larger roots. Rapid treatment and replanting of root rot is imperative to stop the disease spreading to the rest of the affected plant or to other plants and to allow plants to form new roots. Chemical treatments, such as fungicides, chloropicrin and methyl bromide may also be used to limit progression of the disease but must be specific to the responsible pathogen. Some sources claim that cinnamon powder is an effective treatment for reducing spread of root rot, when applied to exposed tissue after removal of diseased tissue. Cinnamon is also claimed to act as a potential fungicide.

Root rot

Scales attack hundreds of ornamental varieties, and are found everywhere ornamental plants are grown. While some scales infest a wide variety of plants, others are host-specific. Many ornamentals are attacked by a single scale species, while others are attacked by numerous species.
Scales damage plants by sucking the juices from the plants. Heavily-infested plants appear unhealthy and produce little new growth. Scales that feed on leaves can cause leaf spotting; spots progressively increase in size as the scales continue to feed. With serious infestations, leaves drop prematurely, and twigs and branches may be killed. The sooty mold that develops on the honeydew produced by soft scales inhibits the plant’s ability to harvest light energy, reducing photosynthesis and further weakening the host plant. Scales that feed on twigs or bark generally do not produce leaf discoloration, but long-term feeding weakens the host plant. A chronic infestation can kill the host.

Periodically inspect host plants, particularly plants that have been previously infested. Since scale insects may occur on all plant parts, check the trunk and branches, as well as the twigs and leaves. The midvein of the underside of the leaf is common site for leaf-feeding scales to inhabit. Stems should be checked around buds, leaf petioles and lenticles or other depressions which may offer a place for the scales to hide and feed. The color contrast between the bark and the scale can be increased by wetting the bark with water before inspecting. Crawlers, the immature mobile life stage, may be monitored for by placing double-stick tape on some branches of the plant.
Stressed plants are more susceptible to scale attack. Maintaining healthy plants will minimize the likelihood of a plant being attacked.
Keep susceptible host plants healthy and well watered; scales nearly always attack stressed plants. Inspect plants periodically for presence of scales. If an infestation is detected, treat before the infestation becomes too severe, and monitor the progress of the treatment in the weeks and months after application. Be aware of the most commonly occurring scale problems in your area. Annual applications of soil-systemic insecticides to susceptible ornamentals are a good idea, particularly if plants are under stress.

Armored scale insects would be a breeze to eliminate if not for their thick outer coatings. The insects themselves are quite vulnerable, so you don’t need to go in with a huge arsenal. Horticultural oil is the very best way to destroy armored scale while preserving the predators that will readily feed on their young during the mobile “crawler” stage. Ideally, timing your application with the emergence of crawlers from their mothers’ covers will eliminate an entire generation all at once. Repeat sprays at five to six week intervals will knock the colony back, and persistence will destroy them entirely. Before applying horticultural oil, ensure that your plant is well hydrated and not heat stressed. Most plants won’t have a problem with horticultural oil mixed appropriately, but the odd bush or tree might experience phytotoxicity, so try a small spot first a few days ahead of when you plan to spray the whole plant.
It also is important to remember that it may take weeks or even months before complete control is observed. Control is delayed if the host plant is under stress, as uptake of the systemic insecticide is slowed. Judging efficacy is complicated by the fact that the scale shells often remain on the plant long after the insecticide has killed the insect underneath. After application, test for efficacy by scraping the shell off the plant and looking for the soft, pulpy insect underneath. If only dry shells are scraped off, then the treatment probably was effective.

Armored and Soft Scales

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 symptoms in the upper parts of the plants cannot be recognized in early stages of root infection.

Diagnosis of this disease is difficult and laborious because infected roots in the soil can only be detected by digging up the soil and observing the roots by eye, trapping mycelia around the infected roots by the bait twig method

Sordariomycetes

- 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

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

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

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

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

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

Leaf spots start as small brown spots, often with a yellow halo, and grow into irregular brown spots (up to 3/4"). Leaf spots sometimes develop a target-like pattern of rings. Severely infected leaves turn brown, curl upward, wither and die.

Avoid overhead watering to limit leaf wetness, and allow enough space at planting time for good air circulation and ample sun penetration. Keep your garden free of fallen leaves all season, and especially thorough at fall cleanup time.

Treatment for Alternaria requires fungicide to be sprayed directly on infected plants, as well as improvements in sanitation and crop rotation to prevent future outbreaks. Organic gardeners are limited to sprays of captan or copper fungicides, making control much more challenging.

Alternaria blight

These insects are so small (a few millimeters in length), that winds can transport them for fairly long distances. They are often green, but might be red or brown, as well. They move quite slowly and cannot jump or hop. Aphids excrete a sugary liquid called honeydew, because the plant sap from which they feed contains excess carbohydrates relative to its low protein content. To satisfy their protein needs, they absorb large amounts of sap and excrete the excess carbohydrates. Honeydew is used as food by ants, honeybees, and many other insects.

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.

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.

Aphididae

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

Symptoms begin as oval to elongate lesions that are generally reddish-brown in color. In the late stages of the disease, erumpent pustules produce numerous black sooty spores. Severe infestations with many stem lesions may weaken plant stems and result in lodging.

Since the fungus overwinters on other plant material, clean up dead plants at the end of the season. Rotate your allium crops to areas that were not previously hosting plants in the family. Remove wild forms of allium, which can also host the fungal spores.

The rust species Puccinia obtegens has shown some promise for controlling Canada thistle, but it must be used in conjunction with other control measures to be effective.

Puccinia

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

Alternaria symptoms once infection begins include small, dark, circular spots that regularly reach ½ inch (1 cm.) in diameter.

Treatment for Alternaria requires fungicide to be sprayed directly on infected plants, as well as improvements in sanitation and crop rotation to prevent future outbreaks. Organic gardeners are limited to sprays of captan or copper fungicides, making control much more challenging. Conventional gardeners can use chlorothanil, fludioxinil, imazalil, iprodine, maneb, mancozeb, or thiram on plants listed on the label of their chemical of choice, but should still strive for prevention in areas with known Alternaria pathogens.

Alternaria

Flowers or leaves may develop silvery streaks. Heavily infested leaves appear brownish or silvery, and growing points may become contorted. Some species of thrips leave sooty spots of black fecal matter on the leaves. Thrips also vector plant diseases.

The main measures you can apply to control this pest are primarily a matter of proper maintenance of the garden. Here’s what you can do to keep away the plants in your garden from a thrip infestation: take care of your garden soil, water it regularly and apply mulch on it. It is known that thrips are attracted to plants that are already ill or unhealthy and thus, they can often be seen on plants growing in harsh conditions, such as in dry land, not irrigated and without mulch on it;
eliminate all vegetal residues, such as dry or wilted flowers;
do not fertilize the soil more than necessary, as this will encourage the growth of other juicy plants, that will attract other pests, such as aphides;
cultivate plants that are adapted to the environment from the area; if you cultivate plants that prefer sun, in a shady and chilly area, they will become more predisposed to thrip infestation.
be vigilant and periodically inspect the plants to see if they have or have not been infested. You can see signs of thrips infestation in the inferior sides of the leaves and in the nip between the leaves and stems. Do not hesitate to remove the already infested plants and to cut the grass and weeds around your home to exclude alternative hosts where thrips could relocate.
do not cut the leaves off of the plants that thrips prefer with a scissor, as this will determine a younger and softer leaf to grow, thus pleasing these pests;
inspecting all the plants you buy before you bring and plant them into your garden;
provide good, constant irrigation to plants;
using row covers, hot caps, or other kinds of cages with a fine mesh in order to keep thrips (and other insects) away from vulnerable vegetables or young plants; once the latter become larger, though, it is important to remove the covers, allowing them enough growing space.

Thysanoptera

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

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

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

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

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

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

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 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.

Lagunkulyariya

(Laguncularia Racemosa)

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