Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Diseases of EggplantPoints to remember about Sclerotinia stem rot:1. Sclerotinia stem rot can affect a very wide range of crops. In eggplant, it causes stem rot at soillevel.2. Black, hard structures called sclerotia, formed on and in the stem, are diagnostic for this fungaldisease. Sclerotia can persist in the soil for many years.3. Several biocontrol products such as Trichoderma sp. can reduce stem rot. Other biocontrolproducts may become available in the future.4. Cultural practices, such as sanitation by removing and destroying all infected plant material, andcrop rotation, help manage this disease.Related exercises from CABI Bioscience/FAO Vegetable IPM Exercise Manual:2-B.4. Use of clean soil: solarization of the seedbed2-C.2. Testing of cultivars3-E.4. Sanitation measures to manage cabbage soft rot (adapt to stem rot)3-B.14. Effects of inundation of fields on incidence of wilt diseases8.4.2 Southern stem rot – Sclerotium rolfsiiSee photo 25 (page 177).Causal organism: fungus - Sclerotium rolfsiiCommon names: Southern blight, Southern wilt, Southern stem rot, stem rot, blackleg, collar rot.Southern stem rot is a serious and widespread soil-borne disease in many parts of the world. It attacks anumber of vegetable crops including tomato, eggplant, bean, cantaloupe, carrot, pepper, potato, sweetpotato, watermelon, and others. In addition, several field crops such as cotton, peanut, soybean, andtobacco can be affected. The fungus can also decay harvested produce, especially carrots.Sclerotium rolfsii is often associated with other soil fungi such as Phytophthora parasitica andRhizoctonia solani, fungi that cause damping-off disease in seedlings or other root and stem rotdiseases.Signs and symptomsThe disease is recognized by wilting and yellowing of leaves; these are often the first symptoms. Whenthe plant is pulled up, roots are softened. The stem is rotten at the soil line (“collar rot”). A white, moldygrowth is evident on affected stem tissues and adjoining surface soil. As the disease develops, tiny,smooth, brown bodies called sclerotia (fungus reproductive structures) are produced on the stem nearthe soil line. The sclerotia are brown in color and look like cabbage seeds while the sclerotia produced bythe fungus Sclerotinia sclerotiorum (see section 8.4.1 above) are larger and black in color. The sclerotiaare diagnostic for the disease.Source and spreadSclerotium rolfsii is a soil-borne fungus. It can survive as sclerotia and in host left-overs in the soil. Acharacteristic of the fungus is that it is generally restricted to the upper 5 to 7 cm of the soil and will notsurvive at lower levels. In most cases, the fungus does not survive in significant numbers when a hostplant is absent for two years or more. However, the sclerotia, which are thick layered, can survive formuch more than 2 years. Any crop rotation schedule should therefore be at least a 3 to 4 year one.The fungus can be spread in running water, in infested soil, on tools and implements, in infectedseedlings, and as sclerotia among the seed. Uncomposted crop residue can spread the infection.Role of environmental factorsWarm weather and high soil moisture, create favorable conditions for the development of this disease.In cooler climates, the disease usually appears in “hot spots” in fields and continues until cooler, dryerweather prevails. The disease is rare in areas with cold winters.154Eggplant Ecological Guide