Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

___________________________________________________________________________________Major Agronomic Practicesregrow. In milder regions of the South of the USA for example, plants are often mowed down to heightsof 15 – 20 cm following the first crop, or the plants are pruned to just above the first side branch. Anadditional dosage of nitrogen and potassium is applied to produce vigorous regrowth and stimulateflowering. This regrowth is often very strong because the roots are already there and can provide thenutrition and water from the soil to feed the new shoots. The second crop is ready to be harvested in 4 to6 weeks. In many parts of Asia, such a second crop is called a ratoon crop.In the Philippines, when severe damage by fruit and shoot borer (Leucinodes orbonalis) occurs, farmerscut back the eggplant crop to about 30 cm from soil level and allow it to regrow. Also when the fruitingstarts to decline and market requirements are high, farmers in Philippines cut back the eggplants in rowsto spread the new production: e.g. by ratooning 4 rows every week. (pers.comm. Julieta Lumogdang,2001). Eggplant in homesteads/kitchen gardens in Lao PDR and Thailand are regularly pruned forprolonged fruit production for home consumption.Ratoon crops in Bangladesh: an example from JessoreAlthough ratooning is not a wide-spread practice in Bangladesh, it can be commonly seen in Jessorearea. In some varieties of eggplant fruiting takes place in flushes. This means fruiting almost stopsafter 2-3 months of the beginning of the fruiting depending on factors like nutrient status, irrigationwater availability etc. After reaching that stage, the farmer cuts down the old foliage of the plant andapplies lots of nitrogen and other fertilizers in rings around the stem and irrigates frequently. Thisresults in new stems and consequentely much earlier fruiting compared to a young crop planted atsame time. This method of ratooning may result in early harvesting. And vegetable prices are directlydependent on the time of availability…!(pers.comm. P.Kumar, April 2001)In summary, reasons for ratooning may include:• Ratooning results in earlier harvesting compared to newly transplanted crops.• Saves costs for seed, and cost for labour like seedbed preparation, raising seedlings, landpreparation, transplanting, etc.• Diseases of seedlings and newly transplanted crops such as damping-off and Phomopsis rot areavoided.• Crops heavily infested with leaf diseases or insects can be cleaned by removing and destroying allfoliage.See also section 4.5 on crop compensation.Staking of plants may be necessary later in the season as the number and size of the fruits increase.Branches should be kept off the ground because fruit touching the ground may spoil. Rain, wind andirrigation can cause the branches to break or droop.Related exercises from CABI Bioscience/FAO Vegetable IPM Exercise Manual:2-C.9. Pruning and crop compensation3.13 GraftingGrafting is forming a union between a shoot (also called scion) and a rootstock of different varieties. Theshoot is joined to a rootstock so that they eventually fuse and grow together. Often, a “wild” cultivar of arootstock which has resistance to certain (soil-borne) diseases is merged with a cultivar which formsgood fruits. With vegetables it is usually done to obtain disease resistance when resistant varieties arenot available. For eggplant, the rootstock Solanum torvum is often used for grafting because it isresistant to Fusarium wilt, bacterial wilt and rootknot nematode. However, there are reports of thebreakdown of the bacterial wilt resistance in S. torvum due to high temperatures (day and night temp.above 30°C) and the occurrence of the virulent group IV strain of bacterial wilt (Date, 1994). Toovercome problems with the soil-borne disease Verticillium wilt (Verticillium dahliae), eggplant can alsobe grafted on a resistant tomato rootstock.41Eggplant Ecological Guide