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esidues on fresh and cooked vegetables, indicating that consumers are also
exposed (UPLB 1990).
In the town of Calamba, situated in the lowlands of Laguna Province, Philippines,
vegetables (tomato, eggplant, string beans, and cucurbits) are grown
for market and local consumption. In response to requests from farmers,
research into integrated pest management (1PM) strategies has been carried
out on several farms. The research described here was carried out on eggplants,
but the approach is applicable to pest management in other crops.
The most serious pest in the cultivation of eggplant is the eggplant shoot borer,
Leucinodes orbonalis Guenée (Pyralidae), which kills young shoots and bores
into fruit rendering it unmarketable. Although recorded in the Philippines as
early as 1948 (Capps 1948), Leucinodes achieved pest status only in the 1970s.
Its outbreak at that time may have been sparked by environmental changes
resulting from increased pesticide use (Navasero 1983). Today, Filipino farmers
rely almost exclusively on pesticides to control the eggplant shoot borer,
which can damage 20-92% of a crop (Esguerra and Barroga 1982; Saavedra
1987).
Minor damage to eggplants is also caused by mites, cutworms, leaf hoppers,
scarab beetles, aphids, and mealybugs. In the dry season, thrips (Thrips palmi)
can cause loss of vigour, leaf yellowing, and eventual defoliation by sucking
plant juices. A complicating factor is that pesticides used on shoot borer can
actually increase the population of thrips (E.N. Bernardo, University of the
Philippines, Los Baños, Philippines, personal communication).
Generally, plant diseases have not been a problem for eggplant farmers and
weeds are controlled by hand. Farmers occasionally clear damaged fruit and
shoots to reduce the population of Leucinodes in the field. Although, Saavedra
(1987) has suggested such manual "cleaning" as a control method, to date
there has been no thorough assessment of its efficacy.
An 1PM strategy for eggplant cultivation must concentrate on insect control
methods that do not cause an increase in the number of weeds or diseases.
Because thrips causes only minor damage in the absence of insecticides, an
inexpensive, nonchemical control package for Leucinodes formed the focus for
this research study.
Several nonchemical alternatives for the control of Leucinodes have been
proposed. For example, Trichograrnma chilonis wasps, which are egg parasites,
have proved to be effective biological control agents of many pests. Baltazar
(1989) recommended regular releases of T. chilonis for control of shoot borer.
Navasero (1983) identified earwigs as a promising predator of larval
Leucinodes. Similarly, Javier (1989) showed that the earwig Euborellia annulata
was an effective biological control agent for another pyralid, the Asian corn
borer.
Both Euborellia and Trichogramma attack only one stage of a pest's life cycle;
thus, employing them in a control strategy requires detailed knowledge of the
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