Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Eggplant Insect PestsPredators such as ladybeetles and hoverflies (Syrphids) andparasitoids like the wasp Diaeretiella rapae and Aphidius sp. areimportant natural enemies of the aphid. See chapter 6 for detailson these natural enemies.In wet years, outbreaks of fungi that kill aphids may occur(Entomophthora sp. and Verticillium sp.). This often coincideswith period of high humidity and rain. Dead aphids may be seencovered with white or green colored fungus growth on the body.These fungi can reduce aphid populations rapidly.Ladybeetle larva and adult: importantaphid predatorsDiscovery of an insect-killing fungusDuring a TOT for Eggplant IPM in Bangladesh, 1997, study fields of yardlong bean (grown as secondcrop) were severely infested by aphids. Aphid populations dropped suddenly, and participantsdiscovered this was due to a fungal infection of the aphids. The participants successfully experimentedwith transferring fungus-infected aphids to uninfected aphid colonies in the eggplant crop (FAO-TOTreport Mymensingh, 1997).Management and control practicesPrevention activities:• Aphid infestation often occurs when plant condition is slightly poor, for example just aftertransplanting, or when too much or too little fertilization is added, or when the soil structure is poor.Healthy, quickly growing plants are the best way of preventing many pests and diseases. Start withselecting healthy transplants, free from aphid infestation (or other pest insects or diseasesymptoms!).• Some varietal resistance has been reported. See table in section 3.2.2. However, there is littlechance of producing an eggplant variety with a durable resistance to aphids. This is because thereare many biotypes (individuals with slightly different genetic characteristics) of aphids are present inthe field and new biotypes can form easily. It is very difficult to produce a variety that has aresistance against all these biotypes.• Sanitation: solanaceous plants that remain in the field after harvest are largely responsible for largenumbers of aphids staying over. Therefore, an effective prevention and control measure is toeliminate as many of these sources of infestation as possible to prevent the aphids from spreading tothe new crop. The crop left-overs can be buried into the soil, fed to farm animals, added to a compostheap or collected to a heap, slightly dried and burnt. Removing crop left-overs is also very valuablefor disease prevention.• Intercropping (planting rows of another crop in the eggplant field) or planting a barrier crop (growingaround the eggplant field) may help reducing aphid infestation. See section 3.15.• Trials to test the use of plastic or aluminium foil mulching to repel aphids in chili cultivation have beenconducted in Malaysia. The best repelling material was aluminium painted plastic sheet, followed bysilvery, white, and yellow plastic sheets. This practice is particularly valuable for crops that aresusceptible to virus diseases transmitted by aphids and thrips. See section 3.11.4 and box in section5.6 under prevention activities.Once aphids are present in the field:• Aphid populations build up rapidly but locally. It is important to monitor plants regularly, both inseedbeds and in the field. When aphids are found but the number of infested plants is low and at thesame time there are natural enemies like ladybeetles present, no additional control measures arenecessary. Remember that low pest insect populations are needed to attract and to feed naturalenemies! Monitor the field regularly to check population growth.• On a small scale, aphids can be washed off the plants with water or with a soap solution. See section4.11.6.85Eggplant Ecological Guide