Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Diseases of EggplantFor reasons not yet understood, ammonia use seems to limit disease development. This may be relatedto slowed fungal growth, altered host susceptibility, or increased populations of antagonistic soil microorganisms.Calcium may also be involved. To the extent that tissue calcium levels are raised, calciumfertilizers may suppress disease by altering host susceptibility. However, normal liming of the soil doesnot change calcium levels in plant tissue enough to protect against S. rolfsii in infected soils.Importance - plant compensation - physiological impactLosses may vary from light and sporadic to almost total destruction of the crop.Sclerotium rolfsii kills host tissue in advance of penetration and then lives on the dead plant tissue.Natural enemies/antagonistsThe antagonistic fungus Trichoderma sp. may be an option for control of Sclerotium rolfsii. See section7.10.1. Other biocontrol organisms may be effective. See section 8.4.1 above, on natural enemies.Management and control practices• Avoid fields where Sclerotium rolfsii occurred before.• Long crop rotations to grasses, buckwheat or corn, which are not susceptible.• Soil solarization (see section 3.10.1.2) for 4 to 6 weeks at 38 - 50 o C is reported to help reducedisease.• Prepare the land properly. The previous crop must be well decomposed prior to planting. This mayrequire deep plowing just before planting. Previous crop left-overs should be buried to depths below10 cm. When crop left-overs are ploughed under to these depths, the fungus cannot survive since itcan grow only on or near the soil surface.• Proper drainage may help reduce disease infection. Preparing plant beds also helps improvedrainage.• Reduce cultivation activities after planting. Cultivation may bring buried plant left-overs back to thesoil surface or throw soil with left-overs against plant parts and this may provoke infection.• Control foliar diseases since dead leaves on the ground may trigger infection. Weeds should also becontrolled early in the season for the same reason.• Botanicals: Ginger (Zingiber officinale) is recommended against Sclerotium rolfsii at a concentrationof 20 g/l water and sprayed 3 times in intervals of 15 days (Stoll, 2000).Points to remember about Sclerotium rolfsii:1. In eggplant, Sclerotium rolfsii causes stem rot at soil level and rot of roots.2. Tiny, brown, hard structures called sclerotia, formed on 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 S. rolfsii. Other biocontrolproducts may become available in Asia in the future.4. Cultural practices, such as sanitation by removing and destroying all infected plant material,proper drainage, and crop rotation help prevent 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 diseases155Eggplant Ecological Guide