Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Diseases of Eggplant3-A.6. Use of subsoil to manage leaf spot diseases in the nursery3-A.7. Soil solarization to manage leaf spot diseases in the nursery3-A.8. Steam sterilization to manage leaf spot diseases in the nursery3-A.9. Test effect of infected crop debris in the field3-A.10. Effect of rain on the spread of leaf spot3-A.12. Test different cultivars for resistance to leaf spot3-A.13. Pruning and plant compensation study3-A.14. Restricted fungicide use to manage leaf spots3-C.1. Symptom development of fruit diseases: classroom exercise3-C.2. Symptom development of fruit diseases: field exercise3-C.3. Use of healthy seed3-C.4. Test of seed health8.2.3 Little leafCausal organism: a mycoplasma-like organism (phytoplasma)Signs and symptomsThe main symptom of this disease is the production of very short leaves. The petioles (leaf stems) are soreduced in size that the leaves appear sticking to the stem. Leaves are very small, thin and pale green.Newly formed leaves are further reduced in size. Shoots of affected eggplant are shorter than normal. Alarge number of buds are stimulated to grow into short branches with small leaves. This gives the wholeplant a bushy appearance. Especially when infection occurs during the early growth stages, plantdevelopment is very much reduced. Usually affected plants do not form flowers.When infection occurs later in the season, the growth of the fruits after infection is restricted or stoppedand the fruits become hard and fail to mature. Seed production is negligible.Source and spreadLittle leaf disease of eggplants is caused by a phytoplasma, a mycoplasma-like organism.This is a tiny organism that lives inside a plant and cannot be seen with the naked eyes.The organism is transmitted by a jassid called Cestius phycitis (previously calledHishimonus phycitis). This jassid is called a vector for this reason. Probably, during the offseasonof eggplant, the mycoplasma survives on weed hosts and from there it istransmitted to a new eggplant crop by insect vectors.In pot tests the vector showed a preference for mycoplasma-diseased leaves, which contained higheramounts of moisture, total carbohydrates, sugars and organic acids than healthy ones. The structure andarrangement of cells in infected leaves apparently favor vector feeding. Also, the bushy growth ofinfected plants favor vector survival and reproduction.Role of environmental factorsUnknown. The disease seems to appear especially late in the season. Probably related to seasonalbehavior of insect vectors.Importance, physiological impact, plant compensationThis disease can be very destructive, affecting large portions of a field.Mycoplasma-diseased leaves contain higher amounts of moisture, carbohydrates, sugars and organicacids (e.g. auxin IAA and cytokinin) than healthy ones. More P and K but less Ca, Mg, total chlorophyland phenols were present in diseased leaves.Root development is also reduced in infected plants. The extent of reduction varies with the eggplantvariety.Natural enemies/antagonistsUnknown.Management and control practicesPrevention activities:• Some varietal resistance has been reported. See table in section 3.2.2. Research is ongoing toselect genotypes with resistance to little leaf disease. Field studies done in New Delhi, India (Das,143Eggplant Ecological Guide