Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

__________________________________________________________________________________Major Eggplant Insect PestsThe fully grown caterpillars come down from the plant for pupation. They hang on a silken threat andpupate on the first surface they touch. This occurs on stems, under dried leaves or debris in soil. Thepupal period varies from 7 to 10 days.Fruit and shoot borer insects are active in summer months, especially during the rainy season. Peakpopulations are often reported in June-August. They are less active during November to February. Thetotal life cycle varies from 22 to 55 days. Development of the different stages of the insect takes longerduring the winter months. FSB populations are reported to increase with average temperature, relativehumidity and rainfall.Host rangeThe FSB feeds on solanaceous plants such as eggplant, tomato and potato and solanaceous weedssuch as Solanum nigrum (e.g. Isahaque, 1983; Das, 1970). FSB has also been reported on othervegetables such as peas but these observations are not confirmed by research.Plant damage and compensationFSB larvae bore into a shoot. While they eat inside of the shoot, the top of the shoot dies. When theshoot dies, the leaves wilt. The rest of the plant may still be healthy. Plants may be able to compensatefor loss of a shoot by producing another shoot but it may take longer before the plant starts to flower andbear fruits. Larvae also feed on flowers, reducing fruit set and yield.FSB larvae prefer fruits to shoots. When fruits areavailable, larvae bore into fruits and start eating the fruitfrom inside. There may be small darkened holessurrounded with brownish areas on fruit surface and/orfruit stalks. The inside of the fruit is hollow and filled withfrass. The fruit is not marketable or fetches a lower price.FSB infestation can be very serious with up to 75% of thefruits being damaged.For sale: FSB Fruits….!In Bangladesh general prices (1997) foreggplant:2 Taka/kg for FSB damaged fruits,10 Taka/kg for undamaged fruits.The problem with FSB is that damage to fruits is irreversible. Once larvae are inside the fruit, damage isdone even when they can be controlled while inside the fruit. Management practices would be mosteffective when focusing on prevention of FSB damage to fruits. For practical reasons, most FSBmanagement is directed towards lowering populations.Natural enemies• Trathala flavor-orbitalis, an ichneumonid wasp, is a frequently reported parasitoid of FSB, for examplein India, Bangladesh and Sri Lanka. It can attack all larval instars (1 st -5 th ) of FSB but prefers the later,3 rd - to 5 th -instar, larvae. One adult parasitoid emerges from one FSB larva. This parasitoid is notspecific to FSB but can also attack the larvae of a number of other insect species like rice leaf folder(Cnaphalocrocis medinalis), the cabbage webworm (Hellula undalis), the sesame pest Antigastracatalaunalis and even a pear pest Numonia pyrivorella. The total time for development of theparasitoid is about 20-24 days. This parasitoid is an important asset to management of FSB becauseit occurs naturally in many areas in SE Asia. In Bangladesh for example, parasitism under naturalconditions was 5% (pers. comm. Md. Atiur Rahman, May 2001). It is unclear whether pesticide useinfluences this figure.☺ Free help for your field work…!?During studies in Bangladesh, parasitoids occurring naturally in the field were studied. Two FSBparasitoids: Trathala sp. and Cotesia sp. were found. The parasitism percentages however, werenot very high: on a 30-day sampling period, an average of 5.8% parasitized larvae per day wasfound in the plot where no pesticides were used, as opposed to 1,3% in the Farmer Practice field(with use of pesticides) (Kumar, 1998).• In Mymensingh, Bangladesh, the parasitoid Cotesia sp. was found in pupa of FSB. Many parasitoidsemerged from a FSB pupa. Unfortunately, also the hyperparasitoids Aphanogmus were found in thesample. These hyperparasitoids parasitize the Cotesia parasitoid! This would reduce theeffectiveness of Cotesia in controlling FSB in that area.71Eggplant Ecological Guide