Ascochyta blight This blight like other blights can be minimized through crop rotation. Also, seed grown in the west is less likely to cause blight. _________________________________________________________________ Asparagus rust Asparagus rust appears as reddish or brownish spots on the stems and leaves of Asparagus. The spots release a cloud of spores when brushed or rubbed. The disease will certainly cause poor quality shoots and often will kill the plant. The problem usually occurs in damp areas, because the spores need moisture to germinate. Plant resistant varieties, such as Mary Washington, in a well drained area to prevent the problem. Control the disease with applications of a fungicide, such as Zineb or chlorothalonil. _________________________________________________________________ Bacterial blight Bacterial blight occurs as large brownish spots with a yellow edge on plant leaves. Decaying of the plant often follows. Select seed grown in the west as a preventative measure and reframe from working in the garden when the plants are wet, as this can spread diseases. _________________________________________________________________ Bacterial canker A canker is a fungus disease which will cause an infected area or lesion on a plant stem. The plant will often die above the infected area, because the canker restricts the flow of water through the stem. Diseased plants are most often removed and destroyed; however the diseased area could be cut out. Sterilize any tools used to remove a canker with denatured alcohol. This will prevent in spreading the disease. As a preventive measure, crop rotation is recommended. _________________________________________________________________ Bacterial spot Leaf spots can be caused by either bacteria or fungi. They come in a variety of colors, shapes, and sizes. Leaf spots caused by bacteria has a water-soaked appearance. Fungi cause leaf spots with a small black dot in the center. One of the most common leaf spots encountered in the garden is a bacterial leaf spot, which is 1/16 to one inch in diameter and dark to tan in color. Crop rotation will help to discourage the problem. Also, select treated seed or resistant varieties. Remove any infected leaves promptly and apply Maneb or chlorothalonil fungicides. An organic approach is to dust the leaves with lime. _________________________________________________________________ Bacterial wilt Wilting occurs because of a lack of moisture in a plant. Bacteria introduced into a plant creates a thick white substance that restricts the flow of moisture in a plant. This problem eventually kills the plant. The bacteria is carried by certain pests that overwinter in or near the garden area. Corn can be attacked by flea beetles that carry the bacteria. Cucumbers and watermelons are affected by cucumber beetles, such as the striped and spotted cucumber beetles that carry the bacteria. Cucumber leaves are the first to be seen to wilt, followed by wilting of the vines. Control the pests that carry the bacteria and you will control the bacteria. A preventive measure is to keep a clean garden at the end of the growing season. This will keep the pests from having a home to overwinter in. Control outbreaks of the pest during the season with the proper pesticides or organic methods. _________________________________________________________________ Black leg Black leg appears as the blackening of the stems at the base of the affected plant. This problem is caused by fungi and bacteria. It is a problem amongst potatoes, brussels sprouts, cabbage, and cauliflower. The cabbage family of plants will also have leaves which turn purplish in color, in addition to the base of the stems turning black. Potato plants will have small leaves at the top of the plant which curl inward. Remove infected plants promptly. Crop rotation will help also. Black leg most often occurs in heavy wet soils, so planting in a well drained soil is recommended. Planting whole seed potatoes could be to your advantage also. Seed potatoes infected by the disease are not always obvious to the eye, so buy seed potatoes from an area that has not been affected by the problem. Planting infected seed potatoes could cause the disease to spread. _________________________________________________________________ Black rot Black rot affects many of the crucifer family of plants including cabbage, cauliflower, and brussels sprouts. The leaves of affected plants will develop wedge-shaped areas yellow in color. Plants will have black or discolored areas inside the stem. Plant in a well drained location to discourage rotting. Purchase plants that are certified as being disease free, such as those that are grown in the far west. Also, purchase seed that has been hot water treated. Remove and destroy diseased plants to prevent the spread of the disease. Frequent crop rotation is advisable. _________________________________________________________________ Blight Blight is a generalized term to cover a wide variety of diseases which affect plants and are caused by fungi and bacteria. The problem does not necessarily cause the leaves to wilt and drop off, but does often cause browning of the leaves and death of the plant. Removal of an infected plant is suggested to hamper the spread of diseases, as well as crop rotation. _________________________________________________________________ Blossom end rot Tomatoes are the most commonly affected plant of blossom end rot, but the problem can happen to other plants as well. The blossom end of the fruit will become brown when the fruit is one third to one half mature. The affected area of the fruit may become depressed or concave. Blossom end rot is basically a deficiency of calcium. Too much or too little water is what causes the plant not to acquire the proper amount of calcium. Also, too much nitrogen fertilizer can cause the plant to grow too fast and not get the calcium that it needs. There are several things that can be done to help with this problem. The first thing to do is to make sure that the pH is about 6.5. Steady growth and not rapid growth is preferred. The same holds true for watering...not too little and not too much. As a rule of thumb the garden requires about one inch per week. Be particularly attentive to proper watering after the plant blossoms, as this is the most likely time for the problem to crop up. Should you try to save an affected plant, try spraying the plant with calcium chloride. _________________________________________________________________ Club root Club root causes a plants root system to become swollen and disfigured. It affects members of the Mustard family, such as cabbage and brussels sprouts. Wilted leaves and stunted growth is likely to occur. The disease is caused by a fungus-like organism called a slime fungi. The disease can remain alive and destructive in the soil for several years. A preventative measure is to raise and maintain the soil pH above 7.0. Crop rotation is also recommended. When purchasing seedlings, inspect the plants for any signs of the disease before purchasing. _________________________________________________________________ Corn smut Corn smut is a fungus that creates massive numbers of black spores. Left unchecked the problem can wipe out an entire corn crop. It appears as a boil-like area on various parts of the corn plant including the tassels, stalks, and ears. The boils are usually greenish-white in color. These will eventually burst, releasing numerous spores. The plants will become stunted and disfigured. The disease overwinters in the soil and on old infected corn stalks. Crop rotation can be helpful. Remove any boils before they burst and spread the disease. Infected plants should be removed and burned. Never use old infected stalks in your compost, as the disease can remain active for several years. _________________________________________________________________ Crown rot Crown rot or Southern stem blight is a fungus disease that attacks the plant on the stem at or just above the soil level. The problem my first be noticed as a white fungus growing at the base of the stem or on organic matter laying on the surface of the soil surrounding the plant. Eventually, sclerotia will develop in the mold. These are small seed-like bodies which are light tan to dark brown in color. The leaves of affected plants will turn yellow and wilt. The plant, as well as surrounding plants, will die. Crop rotation may be somewhat helpful, but removal of affected plants and the soil surrounding the plants is highly recommended. Soil removal is important, because the disease can remain in the soil for over a year. Making sure that all organic matter is plowed under will give the fungus less places to develop. _________________________________________________________________ Damping off Damping-off disease is caused by fungi that live in the soil. The problem causes young seedlings to turn brown, wilt, and die. The fungi can attack the seedlings shortly before or shortly after emerging from the soil. This is a common problem when starting young plants in trays. There are several ways to combat damping-off including the following. Purchase seed which have been treated for the disease. Either sterilize the soil or use a sterile growing media. One such fumigant is called Vapan. Vermiculite and sphagnum moss make an excellent sterile growing mixture. Also, provide adequate drainage for the seedlings as this encourages the problem. If growing the seedlings inside, keep the humidity down. High humidity is known to create a good environment for fungi. In the garden a well drained soil and crop rotation is important. _________________________________________________________________ Downy mildew Downy mildew is not actually a true mildew at all. Unlike true mildews which grow on the surface of leaves, downy mildews originate from within the tissues of the affected plants. Downy mildew appears as yellow, white, gray, or purplish patches on mainly the underside of leaves. The patches are actually the spores of the fungi affecting the plant. Downy mildew can also be seen on stems and fruit. Lima beans, for instance, will develop a white downy mildew on the pods and eventually turn into black patches of mildew. This is a particular problem during long wet periods. Affected leaves will often not develop properly and fall off the plant. Infected plants and diseased leaves which fall off the plant should be removed and destroyed. Crop rotation and adequate water drainage are also helpful. One control of the downy mildew is the chemical zineb. An organic solution to the problem is dusting with lime, flour, or sulfur. _________________________________________________________________ Early blight This fungi causing disease affects potatoes, peppers, eggplants, and particularly tomatoes. It first appears as dark brown or black spots with rings similar to a "target" design. The disease first strikes the lower leaves and then may spread to the upper leaves. The infected leaves will wilt, yellow, and often die. Sometimes the problem will spread to the stems and fruit. Crop rotation is important, as the disease can remain in the ground for about three years. Use seed that has been hot water treated. Treat your own seed with Thiram. Early blight is encouraged by moisture, warmth, and humidity; so provide adequate drainage and ventilation. Control outbreaks of the disease with a fungicide, such as chlorothalonil or Maneb. An organic approach would be to simply remove and destroy infected plants to prevent spread of the disease. Also, avoid working the garden after watering to reduce the chance of spreading diseases. Water early in the morning to give the plants time to dry off. _________________________________________________________________ Fruit rot The rotting of fruit can occur through damage inflicted by insects, garden tools, or simply the fruit laying on a warm, moist soil. These conditions will give bacteria and fungi an opportunity to develop. Fruit may become discolored, slimy, soft, and foul smelling. Overmature fruit can also develop fruit rot. A number of things can be done to discourage fruit rot including the following. Control pests to reduce injury to fruit and spread of diseases. Be careful when working the garden with garden tools. They can inadvertently create open wounds. Keep fruit up off of the soil by staking or mulching. Do not allow ripened fruit to remain on the vine. Crop rotation and proper drainage are also important. Control outbreaks of fungi-causing diseases with the proper fungicide. _________________________________________________________________ Fungus and Bacterial diseases Fungi and bacteria can cause a wide variety of problems. Bacteria are minute plants which can cause rotting, wilting, and the forming of galls. Fungi, which are usually visible to the naked eye, cause rusting, spotting, mildewing, and damping-off. Both are generally encouraged by moisture, warmth, and humidity. Control these problems with the proper fungicide or by removing and destroying diseased plants. Purchase disease-free or treated seeds and plants. Crop rotation, staking, mulching, and adequate soil drainage are also important. _________________________________________________________________ Fusarium wilt Fusarium wilt is a common problem amongst beans, peas, cabbage, sweet potatoes, tomatoes, and watermelon. The disease, which is caused by fungi, will at first cause the lower leaves to curl downwards. Latter, the leaves will yellow and the plant will become stunted. A cross section of the lower stem will reveal dark brown streaks running lengthwise. Purchase wilt-resistant varieties of seeds and plants. Do not plant in a soil that has been infected by the disease. Crop rotation will naturally help. _________________________________________________________________ Internal black spot This disease is one of many affecting potatoes. Prevent this problem by not overfertilizing the plant with nitrogen. _________________________________________________________________ Late blight Late blight is a fungus causing diseases which affects potatoes and tomatoes. It most often occurs in long wet periods of weather. The disease first manifests itself as dark green or black water-soaked spots. Occasionally the affected leaves will have a white powdery mildew on the underside of the leaves. Leaves will droop and appear as though they have been scalded or frost bitten. Fruit will develop rot and decay. Use of the proper fungicide is helpful, but infected plants are usually removed to prevent spread of the disease. Preplan by selecting certified, disease-free seed and plants. _________________________________________________________________ Leaf blight This is a disease which affects carrots. Crop rotation can be helpful to inhibit spread of the disease. Also, purchasing hot- water treated seeds is recommended. _________________________________________________________________ Leaf Spots Leaf spot diseases are caused by fungi and bacteria. Infected leaves have spots which appear as dead tissue. These spots can be yellow-green, tan, or black. The problem is particularly noticed on plants whose leaves are to be consumed, such as turnip greens. The spots will sometimes first appear as dark green water soaked spots. The spots are generally 1/16 to 1 inch in diameter. Remove infected leaves promptly and follow up with an application of fungicide, such as Maneb or chlorothalonil. Also, crop rotation can be a good preventative measure. _________________________________________________________________ Lettuce rot Lettuce rot is caused by the lower leaves coming in contact with the soil. The rotting of the lower leaves will often spread to the rest of the plant. Prevent this problem by applying a layer of sand around the base of the plant. This will improve drainage and keep the leaves from laying on the moist soil which encourages rotting. _________________________________________________________________ Mildew Mildew is a fungus. The term mildew includes powdery mildews, which are true mildews, and downy mildews, which are false mildews. True mildews lie on the surface of the affected plant and feeds on the plant through tiny suckers. False mildews are living on the internal fibers of a plant and appear on the surface of the plant. Mildews come in a variety of colors, but true mildews are generally white in color and occasionally black. Prevent mildew by planting in a sunny, well-drained area. Plenty of air flow and ventilation will also discourage the growth of mildew. _________________________________________________________________ Mosaic Mosaic is a disease caused by a virus. Mosaic can infect beans, peas, corn, cucumbers, melons, peppers, and tomatoes. Infected plants are generally stunted. The leaves of affected plants will have light and dark green areas. This mottled appearance is due to the virus attacking the chlorophyll in the leaves. This will inhibit the plant from creating its own food and cause other disastrous side effects, including distortion of the leaves and fruit. Crop rotation is a good preventative measure. Purchasing disease free, certified seed and plants is also a plus. In addition, control aphids which may carry the virus. One common mosaic is tobacco mosaic which affects tomato plants. The virus is spread by gardeners that smoke. Always wash your hands thoroughly before handling tomato plants if you smoke. _________________________________________________________________ Neck rot The rotting of the necks of onion plants will be less likely a problem with the stronger flavored onions than the milder ones. _________________________________________________________________ Nematodes Nematodes are tiny worm-like creatures invisible to the naked eye. They live and feed off of plant leaves, stems, and roots. This and the laying of eggs in the tissue of the plant will cause knots and stunted growth. Control this parasite through crop rotation and garden sanitation. The use of organic fertilizers and mulches will encourage beneficial organisms, such as fungi and bacteria, to multiply. These beneficial organisms will feed on the nematodes. Also, planting marigolds will help to repel nematodes. _________________________________________________________________ Payllid yellows This is a disease of tomato plants. Cultivating the soil will help. _________________________________________________________________ Pink rot This rotting of onions is bred in moist soil. You can help to prevent this problem by planting bulbs in a well-drained soil. _________________________________________________________________ Powdery mildew Powdery mildew is a true mildew and appears as a powdery or felty white growth on the surface of affected plants. The problem most often occurs during periods of high humidity. This mildew feeds on the plant by means of tiny suckers, draining the plant of important nutrients. Preventative measures of controlling mildew includes providing adequate ventilation and drainage. Applications of sulfur can help to control the problem on beans and peas. Benomyl, karathane, and chlorothalonil may be applied to vine crops, such as melons and squash. _________________________________________________________________ Rhizoctonia To prevent this problem from happening to your potatoes, plant the potato seed shallow in a thick bed of mulch. This will assist the plant in developing faster. Crop rotation is also a good preventative measure. _________________________________________________________________ Ring rot This disease of potatoes is easily spread by garden tools that have come into contact with infected plants. Thoroughly clean garden tools to keep this from happening. _________________________________________________________________ Root knot nematode Nematodes are tiny worm-like creatures invisible to the naked eye. They live and feed off of plant leaves, stems, and roots. This and the laying of eggs in the tissue of the plant will cause knots and stunted growth. In general plant production, quality, and fruit quantity are reduced. Root knot nematodes are one of the most common nematodes. They are particularly prevalent in the southern states where the temperatures are warm and winters are mild. They can remain in the soil for quite some time where these conditions are met. Examine the roots of plants that are suspicioned to have this problem. Take note that knots on the roots of bean and pea plants may not necessarily be nematode- caused. These plants have root nodules which contain beneficial bacteria. These beneficial nodules can easily be removed, whereas the galls created by nematodes are not. Control this parasite through crop rotation and garden sanitation. The use of organic fertilizers and mulches will encourage beneficial organisms, such as fungi and bacteria, to multiply. These beneficial organisms will feed on the nematodes. Also, planting marigolds will help to repel nematodes. _________________________________________________________________ Root rot The fungus which causes this disease will first appear as red or reddish-brown areas on the lower stem and roots of infected plants. These discolored areas eventually spread to the entire stem and root system. Plants infected by this disease may turn yellow, droop, or die. Stunted growth and pod development are also some of the symptoms. Control this disease through crop rotation and by purchasing treated seed. Additional control methods for rot are as follows. Provide adequate drainage, as too much moisture encourages rot. Keep the proper balance of pH and fertilizers. Use a fungicide, such as Capan, or a soil fumigant, such as Vapam. Use a nitrogen- rich fertilizer, but be cautious. Peas produce their own nitrogen and too much nitrogen could cause the plant too produce all vine. _________________________________________________________________ Rust Rust fungi produces spores which appears as reddish-orange spots on the leaves of affected plants. These areas of orange are easily rubbed off when brushed. They can often cause great damage to some crops. Control the disease by applying a fungicide, such as chlorothalonil or Zineb. An organic approach to the problem is dusting the leaves with lime. _________________________________________________________________ Scab This disease occurs as wart-like growths on the foliage and fruit of infected plants. On the tubers of potato plants, the scab can appear as either indented or raised areas of growth. Naturally, crop rotation can help in the control of this fungus disease. Keep the pH level low. Too much alkalinity will only encourage the growth of scab. For organic gardeners this means not to use wood ashes where scab has been a problem. Sulfur is said to be an effective control also. _________________________________________________________________ Scurf Scurf, also known as Soil rot or soil stain, is a disease afflicting sweet potatoes. The fungus, which can remain in the soil for several years, causes brown or brownish-black spots on the tubers. The disease causes the harvested potatoes to shrink in storage. This is particularly a problem in heavy soils. Control scurf by planting seed potatoes which are certified disease-free. If heavy soil is a problem, adding sand to the soil will benefit soil texture. Also, keeping the soil pH below 5.5 is recommended. _________________________________________________________________ Seldom bothered This simply means that the selected plant either has no diseases or that any diseases that do affect it are of little consequence. _________________________________________________________________ Septoria leaf spot Septoria leaf spot is a fungus disease which affects tomato plants mainly in the eastern and mid western states. The disease occurs during very wet periods. The fungus appears as water- soaked spots on the lower, older leaves. These circular spots, usually no more than 1/8 inch in size, eventually turn gray with dark edges. As the disease progresses it will spread to the upper foliage of the plant. All but the topmost leaves may fall off. Even if this does not kill the plant, the lack of foliage may cause the fruit to get sunscald or develop improperly. Advanced stages of the diseases may reveal tiny dark dots in the gray spots which are spores of the fungus. Control the problem by crop rotation, deep cultivation, and weeding of the garden area. Weeds belonging to the nightshade family should especially be destroyed. _________________________________________________________________ Smut Smut is a fungus which produces massive amounts of black spores. The disease can kill the plant or cause stunted growth. Control this disease with crop rotation and removing any infected plants. Also, remove any spore boils before they burst and spread the disease. If setting out plants, use healthy sets. _________________________________________________________________ Spotted wilt Spotted wilt is a virus which is carried by insects called thrips. The disease is a serious problem amongst tomatoes and peppers. Plant death or poor setting of fruit can occur. The young leaves of affected plants curl downwards. Leaves, stems, and fruits may develop dark purple streaks. Also, leaves may have yellow, parchment, or dead-like spots. On the fruit of tomatoes yellow blotches will appear. Control this disease by controlling the thrips which carry the virus. Methods for controlling aphids are as follows. Weed in and around the garden where the thrips live. Apply insecticides, such as Malathion 50% or Diazinon 25% at the recommended rates. A good organic solution is to apply a shiny mulch around the plant. Shiny surfaces have been known to repel the pest. This shiny mulch could be aluminum foil or black plastic mulch which has been spray painted with an aluminum colored paint. _________________________________________________________________ Stem anthracnose This disease is the most common disease afflicting lima beans. The fungus first appears as reddish blotches on the pods of the bean. These blotches may completely cover the pods and cause the pods to drop off of the plant. Advanced stages of the disease will turn the reddish blotches to gray or brown. Red streaks in the veins of the underside of the leaves may appear, as well as reddish spots. Control this disease by purchasing western grown seed or seed that has been hot-water treated. Crop rotation is very important also. Do not save seed affected by this problem, as the disease can be carried by the seed. Try not to work in the garden when it is wet. This is another way in which diseases are spread. _________________________________________________________________ Verticillium wilt Verticillium wilt is a fungus disease which affects tomatoes, potatoes, and eggplants. Initially the lower, older leaves yellow and droop. These lower leaves will fall off and the disease will spread to the rest of the plant. Often only the leaves at the tips of the plant remain. Of course this causes stunted growth of the plant and its fruit. In the case of tomatoes the fruit will remain small and undesirable. Since this disease is soil-born tomatoes, potatoes, and eggplants should not be planted where these same plants have been grown before. Remove any infected plants from the garden immediately and destroy them. _________________________________________________________________ Viruses Viruses cause a variety of problems including yellowing of the leaves, curling of the leaves, blocking of a plant's vascular system, stunting growth, and killing the plant. Viruses are spread by other infected plants and pests which transmit the disease. Pests that feed on the sap of an infected plant can go on to feed on a healthy plant and transmit the virus through its saliva. Controlling pests is one of the best ways to control viruses. Always use disease free plants and remove any diseased plants from the garden immediately. Also, avoid working in a wet garden. This is another way diseases are spread. Sanitize garden tools with denatured alcohol to keep from spreading diseases. _________________________________________________________________ White rot This rotting of horseradishes is controlled by keeping the garden area free of wild horseradishes. _________________________________________________________________ Yeast spot Yeast spots are recognized as grayish brown spots on the seed of lima beans. The yeast fungus enters the bean pods by puncture wounds made by stink bugs. Control the disease by controlling the pest. _________________________________________________________________ Yellows This disease of cabbage is controlled by purchasing disease resistant varieties. _________________________________________________________________