Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Eggplant Insect PestsManagement and control practicesWhitefly management in a crop will depend on the severity of damage caused in that crop, and thenumber of whiteflies required to cause this damage. Very few whiteflies are required to transmit viruses,so where this is the major concern, a farmer will want to avoid even small numbers of whiteflies. Wherelow levels of whiteflies are tolerable, which is the case in most eggplant growing areas, other methodssuch as biological control can be more effective.Prevention activities:• Plant resistant or tolerant eggplant varieties where available. Some resistance has been reportedfrom India. See table in section 3.2.2. Check local seed supplier in areas where whitefly is a seriousproblem.• Proper monitoring of the whitefly population should be done regularly to detect early infestation. Theeasiest method of monitoring for whiteflies is leaf inspection. Sampling 100 leaves per field (one leafon each of 100 randomly selected plants) can provide a very good estimate of the average whiteflypopulation density in the field, but fewer samples are usually all that is needed to make amanagement decision. Check for natural enemies, they may be many of them!• The movement of whitefly adults can be monitored with yellow sticky traps. This method can providea relative measure of general population trends over an extended area. In China for example, thesetraps are widely used in both greenhouses and in the open field. Careful monitoring of the types andnumbers of insects caught on the traps should be done as yellow traps may also attract largenumbers of useful natural enemies! When this happens, the traps are better removed from the field.• Destroy old crop residues that harbor whitefly infestations unless large numbers of natural enemies ofwhitefly are detected. Destroy all crops residues infected with virus.• Susceptible crops should not be grown continuously because whitefly populations expand rapidly ifthere is a continuous supply of food.• Avoid planting next to crops infested with whitefly and avoid carry-over from infested plant material.• To protect seedlings, insect netting or screen cages of very fine wire mesh, placed over nurseries,helps reducing initial whitefly infestation of young plants. This is especially useful to prevent earlyinfection with virus diseases, transmitted by the whitefly. Floating row covers (generally made out of alight fiber mesh and placed over newly planted crops) also exclude whiteflies during the vegetativegrowth of the crop. Screen cages and floating row covers work very well for early-season protection,but can be expensive. For eggplant, it is probably too expensive to consider.• Under field conditions, there are several types of barriers that can reduce whitefly problems. Theseinclude reflective mulches that tend to repel whiteflies, oil-coated yellow mulches that act as a trap forwhiteflies, and intercropping. For example, intercropping tomato with sorghum reduced whiteflypopulation and had the best yields and effects on predators (Tumwine, 1999).• Planting time also can be an effective tool to avoid whiteflies because they reproduce more rapidlyunder hot, dry conditions. Thus, planting during or shortly after rainy season allows crops to beestablished and even mature before conditions are favorable for rapid population increases.• Establishing a host-free period by careful choice of planting site and date is now a commonlyaccepted recommendation for reducing whitefly populations in many areas of the southern U.S.A. thatare severely affected by this pest. This practice requires regional cooperation to be effective.• Avoid unnecessary applications of pesticides to prevent secondary outbreak of whiteflies (due toelimination of natural enemies).93Eggplant Ecological Guide