Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Diseases of EggplantRelated exercises from CABI Bioscience/FAO Vegetable IPM Exercise Manual:3-B.1. Seed drenching/coating to manage damping-off3-B.2. Use of subsoil to manage damping-off in the nursery3-B.3. Soil solarization to manage damping-off in the nursery3-B.4. Steam sterilization to manage damping-off in the nursery8.1.2 Root rot – Phytophthora sp.Causal organism: fungi – Phytophthora sp.If part or all of the roots are destroyed by a pathogen, the plant has a rootrot. If the rot progresses so that the entire root system is destroyed, theshoot then collapses as well. Root rots can attack many vegetables. Ineggplant, root rot is caused by Phytophthora capsici and in tomato it iscaused by the fungi Phytophthora parasitica and Phytophthora capsici.Root rots in other vegetables may be caused by a complex of other soilfungi, including those that cause damping-off disease, like Fusariumsolani, Rhizoctonia solani, and Pythium sp.Roots affected byPhytophthora sp.(from: Blancard, 1992)Signs and symptomsPart or all of the root system of the plant is destroyed. At soil level, darkgreenish,water-soaked spots occur which often girdle the stem, causing the plants to wilt and die.Diseased plants appear in patches in the field, with the location and size depending on weather and soilconditions.Leaf spots may develop, which are often water-soaked and irregular in shape, later becoming a lightbrownshade. The fruit shows similar spots often enlarging to cover the entire fruit, which later dries andbecomes mummified.Source and spreadFungi causing root rots are soil inhabitants. They can spread by soil particles attached to transplants,field tools, slippers or shoes, etc. or with ground water.Role of environmental factorsThe fungus causing root rot in eggplant is most active in moist, warm weather. Both damping-off and rootrots occur in areas with poor drainage (=high soil humidity) and/or areas with a previous history of thedisease.Root damage from salts (for example caused by too much fertilization) and soil compaction can also leadto increased loss due to root rots. If a field has symptoms of root rot, the plants that survive are probablyalso damaged and may have lower yield or show disease symptoms when stressed later in the season.Natural enemies/antagonistsTrichoderma sp. is an effective antagonistic fungus that can reduce root rot. See section on damping-offabove and section 7.10 for more information on Trichoderma.Management and control practicesSame as for damping-off disease. See section above.Deep planting, planting into cold, wet, or poorly prepared soils, low soil fertility and use of old or poorquality seeds can all increase the incidence of damping-off and root rot disease.Points to remember about root rot:1. Root rot is caused by soil-borne pathogens.2. Root rot occurs in areas with poor drainage or areas with a previous history of the disease.3. Optimizing drainage and growing conditions, using vigorous seed, rotation of the nursery site andsanitation practices (removing crop left-overs) are ways to prevent disease problems.4. Good prevention of damping-off can be achieved by adding compost or other decomposed organicmaterial (15 to 20 tons/ha) to the soil regularly and before sowing or transplanting.5. Additional prevention can be obtained with application of the antagonistic fungi Trichoderma sp.134Eggplant Ecological Guide