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in the field. These pests were the main cause of lower yields during the dry
season in sprayed experimental plots and in the adjacent farmer's field compared
with unsprayed plots. The best control for thrips and mites seems to be
avoiding the use of insecticides.
Light traps and sticky traps used in this study failed to catch any Leuci nodes.
This species may not be attracted by visual stimuli, but inadequacy of trap
design may be the problem. A pheromone trap with live female bait was most
effective for catching adult Leuci nodes. During 41 nonconsecutive nights of
trapping, this trap caught an average of 35 males/night, with a peak catch of
282.
Adult female Leucinodes are short-lived (2-3 days in a trap) and the tendency
toward synchronous populations makes it difficult to rear a continuous supply.
An attempt was made to extract the female sex pheromone to prolong its
use in the field. Early results indicate that the extracted pheromone is not as
attractive as live females, but with better understanding of Leucinodes mating
behaviour, pheromone trapping may prove to be useful in controlling this
pest. It will at least provide a valuable tool for monitoring purposes.
Earwigs were collected from the natural population in the eggplant field. In
the dry season, an unidentified species was found in low numbers. In the wet
season, Euborellia annulata was abundant. Only E. annulata was found inside
eggplant fruit, in an empty Leucinodes tunnel. E. annulata is probably the
species that preys on Leucinodes and was the species observed by Navasero
(1983).
The total yield of class A and B fruit from February to June differed by only
4% between the experimental field and the farmer's field. The yield from the
experimental field was higher on most harvest days in the dry season (until
mid-May), but the yield from the farmer's field was usually higher in the wet
season (Fig. 2). In the dry season, the yield from the farmer's field was reduced
and plant growth was stunted by thrips and mites. Because the experimental
field plants were taller, they suffered more damage from wind and rain later
in the year. Fallen plants were more susceptible to plant pathogens, so marketable
yield from the experimental field was reduced. Staking proved to be
too labour-intensive and not very effective.
Unsprayed eggplants were sold at UPLB nine times between 14 March and
19 April. The price was set 10-50% higher than Los Banos market prices to test
whether consumers placed a higher value on pesticide-free produce. Sales
were promoted by posters, telephone, and word of mouth. Response was
positive, with weekly sales averaging 61 kg; many customers inquired about
the availability of other unsprayed vegetables.
The costs of spraying and individual treatments (Table 3) were deducted from
the gross income generated from the farmer's field and experimental field.
With these adjustments, together with the higher prices paid for unsprayed
eggplants, the income from the experimental field was 24% higher (Fig. 3):
324