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.

Signs of damage

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.

How to prevent

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.

Treat

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Chrysanthemum white rust

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

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

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

The spores are hyaline, of various shapes, and are released through a circular apical pore.

To prevent powdery mildew from forming in the first place, avoid low-temperature, high-humidity environments. Do not crowd plants. Do not grow susceptible plants in the shade. Water the soil, not the plants.

Use sulfur-containing organic fungicides as both preventive and treatment for existing infections.

Leotiomycetes

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

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

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

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

Peronosporea

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

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

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

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

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

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

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

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

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.

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.

Thysanoptera

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

Phytoplasmas can infect and cause various symptoms in more than 700 plant species. One characteristic symptom is abnormal floral organ development including phyllody, (i.e., the production of leaf-like structures in place of flowers) and virescence (i.e., the development of green flowers attributable to a loss of pigment by petal cells). Phytoplasma-harboring flowering plants may nevertheless be sterile. The expression of genes involved in maintaining the apical meristem or in the development of floral organs is altered in the morphologically affected floral organs of phytoplasma-infected plants. A phytoplasma infection often triggers leaf yellowing, probably due to the presence of phytoplasma cells in phloem, which can affect phloem function and carbohydrate transport, inhibit chlorophyll biosynthesis, and trigger chlorophyll breakdown. These symptoms may be attributable to stress caused by the infection rather than a specific pathogenetic process. Many phytoplasma-infected plants develop a bushy or "witch's broom" appearance due to changes in their normal growth patterns. Most plants exhibit apical dominance but infection can trigger the proliferation of axillary (side) shoots and a reduction in internode size. Such symptoms are actually useful in the commercial production of poinsettias. Infection triggers more axillary shoot production; the poinsettia plants thus produce more than a single flower.

Phytoplasmas are normally controlled by the breeding and planting of disease-resistant crop varieties (perhaps the most economically viable option) and by the control of insect vectors.

Plantibodies targeting phytoplasmas have also been developed. Tetracyclines are bacteriostatic to phytoplasmas.However, disease symptoms reappear in the absence of continuous antibiotic application. Thus, tetracycline is not a viable agricultural control agent, but it is used to protect ornamental coconut trees.

Phytoplasma

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

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

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

Southern blight

Yellowing and shrivelling of lower leaves. Some or all of the plant suddenly wilts, especially in hot weather. Plants may recover in cooler or wetter conditions. Brown or black streaks in the tissue under the bark. These are visible as a circle or part-circle of brown marks, if the stem is cut across transversely, or as brown lines if it is cut lengthways. In woody plants the marks are often in the outer (most recent) growth ring, although older infections that were not fatal may have left similar marks in older, inner growth rings. However, a few plants, such as chrysanthemums and roses, don't usually show these marks when infected. Branch dieback is a common symptom in trees and shrubs. Sometimes only part of the plant may wilt and dead branches may indicate infections which occurred in previous years.

Water the plant regularly, and when possible, provide afternoon shade. Fertilize on schedule, using a low-nitrogen, high-phosphorus fertilizer. Prune off dead and dying branches. You can often get rid of the verticillium wilt fungus in the soil by solarization.

There is no effective treatment for verticillium wilt. For affected vegetables, remove and dispose of the plant; don't compost it. For landscape plants, prune out affected branches and dispose of them immediately. Do not use infected wood for chips for landscape mulch.

Verticillium wilt

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

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

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

Stems will be leggy or stretched out. Leaves turn yellow. Leaves are too small.

Arrange the light sources so that the plant receives the required number of photons.

Make sure your plant gets not too much/not too little light.

Light-related issue

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

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

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 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

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

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

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

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

Magnesium deficiency

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

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

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

Pestalotiopsis leaf spot

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

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

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

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

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

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

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

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

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

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

Phytophthora blight

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

All the visible and otherwise detectable changes in the infected plants make up the symptoms of the disease. Symptoms may change continuously from the moment of their appearance until the entire plant dies or they may develop up to a point and then remain more or less unchanged for the rest of the growing season. Symptoms may appear as soon as 2 to 4 days after inoculation, as happens in some localized viral diseases of herbaceous plants, or as late as 2 to 3 years after inoculation, as in the case of some viral, mollicute, and other diseases of trees. In most plant diseases, however, symptoms appear from a few days to a few weeks after inoculation.

Put weather stripping around your windows and doors, and replace any stripping that is worn; Keep any outdoor lights off, and turn off as many lights inside your home as possible, as stink bugs are attracted to light; Pull down window shades and blinds to keep the light from spilling outside at night.

You can either use silicone based caulk to cover the cracks or screens for windows and doors, or you can also spray the exterior of your home in the fall, for a plus of protection. You can use natural pesticides against these insects, if you prefer not to fill your home with chemical pesticides.

Pentatomidae

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

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

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

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

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.

Planting resistant crops is the ideal form of disease prevention, however, mutations can give rise to new strains of fungi that can overcome plant resistance. Although the disease cannot be stopped by removal of the alternate host, the life cycle is disrupted and the rate of mutation is decreased because of reduced genetic recombination. This allows resistance bred crops to remain effective for a longer period of time.

Macrocyclic Disease: Developing a management plan for this type of disease depends largely on whether the repeating stage (urediniospores) occur on the economically important host plant or the alternate host. For example, the repeating stage in white pine blister rust disease does not occur on white pines but on the alternate host, Ribes spp. During August and September Ribes spp. give rise to teliospores which infect white pines. Removal of the alternate host disrupts the life cycle of the rust fungi Cronartium ribicola, preventing the formation of basidiospores which infect the primary host. Although spores from white pines cannot infect other white pines, survival spores may overwinter on infected pines and reinfect Ribes spp. the following season. Infected tissue is removed from white pines and strict quarantines of Ribes spp. are maintained in high risk areas.

Pucciniales

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

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

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.

Autumn Squill

(Prospero Autumnale)

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