As a result of the green revolution, the use of yield-increasing inputs
such as fer- tilizer and pesticides became a matter of course in
irrigated rice farming in Southeast Asia. Pesticides were applied
liberally, both as a guarantee against crop failure and as a means of
fully utilizing the existing yield potential of the crops. However,
since outbreaks of pests, such as the brown planthopper (BPH) or the
tungro virus, continued to occur despite the application of chemicals, a
change of approach began to take place. It is now being realized more
and more in Southeast Asia that crop protection problems cannot be
resolved solely by the application of chemicals. In the past several
years, increasing efforts have there- fore been made to introduce, as a
first step, supervised crop protection, leading gradually to integrated
pest management (Kranz, 1982). Although the crop protection problems
naturally differ in the different devel- oping countries in Southeast
Asia, the economic situation prevailing in these countries can
nevertheless be regarded as an important common determinant: pesticide
imports use up scarce foreign currency and thus compete with other
imports essential to development. For the individual rice farmer, the
problem is basically the same: his cash funds are limited and he must
carefully weigh whether to use them for purchas- ing pesticides,
fertilizer or certified seed. In view of this constraint, it is becom-
ing necessary to abandon the purely prophylactic, routine calendar
spraying and instead, employ critically timed and need-based pesticide
applications.