Phytophthora blight of peppers, caused by the fungus, Phyrophthora capsici, is one of the most serious diseases that attacks the crop. Under ideal environmental conditions for the fungus, the disease can result in a complete crop loss prior to the first harvest. However, in most years the disease occurs in late July through August following periods of high rainfall with warm temperatures. One of the most important environmental factors necessary for Phytophthora to infect peppers is high soil moisture. The fungus produces spores that must swim to the plant in order to cause infection. Therefore, infection will only occur when the soil is saturated. Disease management strategies are directed towards production of the crop in a manner that minimizes the development of saturated soil conditions around the base of the pepper stem. Disease management strategies include production of the crop in well drained fields; use of waterway systems, drainage ditches, underground drainage tiles, etc.; production of the crop on well constructed raised beds; avoiding the occurrence of a furrow on top of the bed during transplanting or cultivation; filling in depressions made by transplanting equipment used for plastic mulch culture; and providing a drainage ditch at the end of fields to allow excess soil moisture to leave the field between beds during heavy rainfall periods.
Once fields are properly prepared to allow for maximum drainage, other disease management practices should be integrated into the crop production system. Crop rotation away from peppers, eggplants, tomatoes, and all cucurbits for at least 3 years, and/or the use of soil fumigation will reduce the population of the fungus in the soil. Recently released bell pepper varieties, Emerald Isle (Harris Moran) and PP3135 (Rogers Seed), possess resistance to Phytophthora and should be grown whenever possible. The use of the fungicide, Ridomil Gold 4E, at transplanting, 30 and 60 days later will help protect the plant from infection. Application of a copper fungicide + a spreader sticker as a foliar spray beginning 14 days after the last Ridomil Gold 4E application and continued every 7-10 days until the end of the season will provide protection of the crop from the aerial phase of the disease.
Once any pepper plants become infected during the season they should be removed from the field or disced into the field as soon as possible. With plastic mulch culture once plants wilt and die, a 5-ft wide section of plastic mulch should be removed between infected plants and healthy plants down the row. This will help to prevent spread down the row from diseased plants. For bare ground culture fields, areas of infected plants should be disced once they appear in order to prevent movement of spores from infected plants to healthy plants during subsequent rainfalls.
Successful management of Phytophthora blight on peppers involves all of the above mentioned strategies. It is imperative that cultural practices designed to improve soil drainage are addressed before considering the use of resistant varieties and fungicides. Disease management will only be accomplished when as many control strategies are integrated in the pepper production system as possible.
Stephen A. Johnston,
Extension Specialist in Plant Pathology
Rutgers Agricultural Research & Extension Center, 121 Northville Road, Bridgeton, NJ 08302
Reprinted from: Proceedings. 1997. New England Vegetable and Berry Conference and Trade Show. Dec.16-18, 1997. p.66.
Other phytophthora articles on UConn Vegetable IPM site:
Pepper IPM
One Darn Good Reason to Rotate: Phytophthora
This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.
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