and Integrated Pest Management - part - usaid

78 PI"S'I1CIDF MANAGEMENI' AND IPM INSOUI IEAST ASIA
The impact of the large numbers of beneficial organisms, although minimal
in controlling the leaffolder infestation, was critical in suppressing the
potentially dangerous hopper population (Fig. 2). The hopper population was
made up of the brown planthopper, whitebacked planthopper Sogatellafurcifera,
and the green leafhopper Nephoiteix virescens. The primary beneficial
organisms observed and counted weekly were Lycosa sp. (spider), Cyrtorhinus
sp. (mirid), Metioche vittaticolis (sword-tailed), and Microspis crocea
(coccinellid), and there was no difference in the numbers of these beneficials in
tile Bt and untreated plots. As demonstrated in Fig. 2, the planthopper
population has never reached the insecticide treatment level (threshold) of 1
hopper/tiller despite an early infestation (20-30 DT). There are numerous
reports of the importance of these beneficial spiders and insects in controlling
these hoppers (Chiu 1987, Heinrichs et al. 1978, Vorley 1985). Severe hopper
outbreaks and resurgence resulting in hopperburn and complete yield loss are a
direct result of the indiscriminate use of broad-spectrum insecticides that are
extremely toxic to these piedatory insects and spiders.
Number of insects/m
35
z
30 UNTREATED
25
20
15
0