WHITEFLY POPULATION FLUCTUATION AND GOLDE N MOSAIC INCIDENCE IN BEAN

Bean golden mosaic (BGMV) is an economically pernicious disease in Lat in America, especially in Brazil. With the objective of studying the f luctuation of the vector population and its relation to the variation of bean golden mosaic incidence and to the climatic conditions (temper ature and rain), this research was carried out from 1994 to 1995. Earl y in September, the whitefly population sizes were small but increased steadily up to February, when the bean golden mosaic incidence was al so at high levels. In March, even with high vector populations moving from soybean fields, there was no increase in this disease incidence, which indicated that a greater proportion of the flies were not virule nt. The decrease in vector population was related to low temperatures, specially to the minimum temperatures in April; nevertheless, the bea n golden mosaic incidence was constant. It was concluded that small wh itefly populations may be sufficient to promote BGMV epidemics, given that the number of virulent whiteflies rise due to successive bean pla ntings in time and to the presence of the virus/vector hosts.