Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Diseases of Eggplant• Crop rotation: Eggplant should be rotated with plants other than tomato, potato, pepper, and othersolanaceous crops in a schedule of at least two, and preferably three, years.• Crop remains should be removed and destroyed immediately after harvest. Make a compost pile andcover it with a layer of soil. Do not use this compost on eggplant or any susceptible crops unless it iscompletely decomposed. Infected crop left-overs is a very important source of new infection!• When possible, avoid planting solanaceous crops adjacent to the eggplant field if they will maturebefore the eggplants. Such plantings can be a massive source of spores for the planting that willmature later.• Infection rate can be reduced by maintaining good plant vigor and minimizing injury to plants. Plantvigor is influenced by several factors including adequate fertilization and proper moisture contents ofthe soil during transplanting and growing. Increase the organic matter in the soil as much aspossible, especially by using well decomposed manure. This will increase fertility. The use ofnitrogen fixing legumes in the crop rotation scheme can also increase the fertility of the land andeliminate some of the inoculum.• When possible, limit leaf wetness period, which promotes sporulation and infection, by not usingoverhead irrigation or irrigating early in the morning to allow quick drying of the leaves. Also avoidgrowing eggplant in shady areas or areas with little wind as this will increase leaf wetness period.Once disease symptoms are found:• Fungicides can reduce the rate of infection. The need for fungicides depends on the time of diseaseappearance and the rate of disease spread. Sometimes, pruning of the older leaves (and removingthese from the field!) may already reduce a good portion of the infection. Usually, fungicideapplications should begin when early symptoms of early blight are detected. Most fungicides willprovide a layer on the leaves to prevent spores from germinating. As new leaves form regularly andrain may wash the protective fungicide coating off the leaves, the fungicide need to be appliedregularly. How often depends on disease incidence, growth stage and weather conditions.Sometimes, 7- day intervals are used when the weather is cool and damp, and up to 10-day intervalswhen the weather is dry. Regular monitoring of the field is very important to establish such aschedule! Trials can be set up to check the importance of early blight and the efficiency of such aspraying schedule. It might be worth trying to establish some kind of spraying threshold: e.g. when acertain number of lesions appear, then a spraying schedule of different interval can be tested.Disease-forecasting programs have been developed to predict the rate of early blight developmentbased on weather patterns. Such programs could enable farmers to better time their fungicideapplications but the success of forecasting programs varies.• Ratoon crop: cutting the plants back and allowing regrowth may also be worth trying when blightinfestation is severe. See section 3.12. It is important to remove all plant material from the field anddestroy it. Old leaves may still be a massive source of infection for the new shoots.Points to remember about early blight:1. Early blight is a serious disease that can cause death of plants and severe loss of fruits.2. Most management practices focus on prevention or delay of infection.3. Sanitation, such as pruning infected leaves is a good control method and it prevents spread ofthe fungus. However, too much pruning results in lower yields.4. Once early blight infection occurs and environmental conditions are favorable for its spread,the disease is hard to control by just sanitation. Fungicide application may be needed.However, the timing and number of fungicides applications can be changed by studying thedisease in the field.5. When severe infection reduces yield, it may be worth cutting the whole plant back and allowregrowth (ratooning).Related exercises from CABI Bioscience/FAO Vegetable IPM Exercise Manual:3-A.1. Study of symptom development of leaf spots: classroom exercise3-A.2. Study of symptom development of leaf spots: field exercise3-A.3. Effect of infection of the seed bed3-A.4. Effect of the use of infected planting material3-A.5. Test effect of hot water seed treatment142Eggplant Ecological Guide