Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

___________________________________________________________________________________Major Agronomic PracticesSeed-borne diseasesSeed can become infected with fungal spores or bacteria (seed-borne diseases). Infection can occurduring the growing season, when seed is still on the plant or it may occur after the seed has beenextracted from the plant. Common seed-borne diseases of eggplant are early blight (Alternaria solani),and fungal wilt (Fusarium and Verticillium).Most seed companies do not normally treat eggplant seed. Instead, the growing conditions of the seedproduction fields are thoroughly checked. Only when a seed-borne infection is suspected, seed lots maybe treated with diluted hydrochloric acid or sodium phosphate. Other sterilization methods are listedbelow.Soil-borne diseasesSeed can also become infected after it has been sown in the soil. Pathogenic fungi or bacteria living inthe soil (soil-borne diseases) may attack the seed and cause death of the seed or the emerging rootseven before the seedling has emerged above the soil. A common soil-borne disease affecting seed andseedlings is damping-off, caused by a complex of fungi. See section 8.1.1.When to treatWhen seed is bought from reliable seed companies, it will usually be disease-free. When seed is locallyproduced, it is probably better to sterilize it before sowing. When soil has given problems with dampingoffdisease before, it can be helpful (next to cultural practices such as rotation, and possibly soilsterilization, see sections 3.10.1 and 3.17) to coat seed before sowing.It should be noted that seed treatment methods may reduce germination percentage!How to treatThere are four main methods for seed treatment:1. Physical: by soaking seed in hot water.2. Chemical: by sterilizing seed with chemicals or by coating seed with a layer of fungicide.3. Botanical: by coating seed with a layer of plant extract.4. Biological: by coating seed with a layer of antagonistic fungi (see also section 7.10).None of these treatments will completely prevent pathogen attack in all circumstances!In addition to seed treatment, it is important to select a field that is free of soil-borne diseases. Somemanagement practices for soil-borne diseases include crop rotation (using soil that has not been used forgrowing eggplant or other solanaceous crops for at least 2 years) and the use of resistant or toleranteggplant varieties. See also sections 3.2 on variety selection, 3.7 on soil, 3.10 on nursery management,3.17 on crop rotation, and second box in section 3.7.3.3.6.1 Physical seed treatmentTo kill fungal spores or bacteria attached to or within the seed, seeds should be soaked in hot water at50 o C for 30 minutes.The right water temperature and the right duration are very important. If the water is too cold, thepathogens are not killed. If the water is too hot, seed germination will be greatly reduced.The easiest way to treat seed is to heat water to 50 o C on a small fire or burner. Carefully check the watertemperature with a thermometer. Pour the 50 o C water into a thermos flask and add the seeds. It may beeasy to wrap the seeds in a cloth to keep them together. Leave the seeds in the flask for 30 minutes.After soaking in hot water, the seeds are placed in clean, boiled, cold water to cool down. Dry byspreading the seeds in a thin layer on paper or on cloth.In some cases, a fungicide coating is applied after hot-water treatment. See section 3.6.2 below.13Eggplant Ecological Guide