ABSTRACT

Weather is the most important factor that determines the geographical distribution and periodic abundance of crop insect pests and parasites of an­ imals. Weather controls the development rate, survival, fitness, and level of activity of individual insects; the phenology, distribution, size, and continu­ ity of insect populations; migration and their establishment; and the initia­ tion of insect outbreaks (Pedgley, 1990; Drake and Farrow, 1988). Weather influence can be immediate, cumulative, direct, indirect, time lagged, ex­ ported, or imported. Indirect effects arise through host quality and parasite populations. A time-lagged influence is one that occurs at a later stage as a consequence of both past and current weather. Imported/exported influ­ ences arise because insects are highly mobile, and outbreaks may be initi­ ated by windborne migrations (Drake, 1994; Baker et al., 1990).