Onion Downy MIldew
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Onion Downy Mildew .jpeg) Onion downy mildew is a fungal disease that can survive in the soil for up to five years. It also lives in crop debris and on infected plants, not all of which will show symptoms. Onion downy mildew for example, overwinter in seemingly healthy planted allium plants, acting as a source of infection for the spring planted crop.Susceptible Plants- members of allaceae, eggplant Symptoms- The first evidence of disease is a fine, furry, grayish white to purple growth on the surface of older leaves. Leaf tissue under the growth becomes pale green, then yellow, and finally collapses. Large, yellowish, circular clumps of infected plants, a few to many feet in diameter, may be the first symptom noticed in the field. The yellowing patterns often enlarge in the direction of prevailing winds. Bulbs may rot in storage. Onion downy mildew is worst in cool, wet season. Prevention and Control- Use a five year crop rotation where onion downy mildew has occurred. Do not save seed from infested onions/ Break the cycle- give up growing autumn and spring planted onions for a year or two. Remove infected plants as soon as they are discovered. Remove weeds to encourage good air flow around the plants. Currently there are a few red onion cultivars such as Calred that are resistant to onion downy mildew. Fungicide Control- Arbico Organics carries a product called Oxidate which uses peroxygen chemistry – rapid oxidation that kills a wide range of bacteria and fungi on contact. With this OMRI-listed weapon, organic farmers can fight Onion Downey Mildew and other such disease causing pathogens. A wide variety of crops that suffer from these – onions, melons, tomatoes, peppers, snap and dry beans, strawberries, cole crops, and mushrooms – can now be treated safely and repeatedly to prevent continuing outbreaks. Because of its mode of action, there can be no resistance developed to OxiDate’s continued use. It is exempt from pesticide residue considerations and is EPA registered. . For all fungicides, thorough coverage of foliage is important in the control of downy mildew.
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