Many soybean fields have yet to be planted across Iowa or have not emerged because of the cold, wet soils. So how does this situation affect the bean leaf beetle? Delayed soybean emergence is unlikely to greatly affect the survival of overwintered beetles. Bean leaf beetles can sustain themselves on alfalfa and other legumes before soybean is available. Females do not lay eggs in alfalfa and will wait until soybean emerges from the soil. Therefore, delayed soybean emergence can diminish both the number of beetle eggs laid in a field (thereby decreasing the next population) and the incidence of bean pod mottle virus. Each day that soybean emergence is delayed is another day in which beetles are not laying eggs or spreading bean pod mottle virus among seedling plants. From the standpoint of integrated pest management, delayed soybean emergence thus aids in suppressing the damage caused by the beetle and the virus.
This article originally appeared on pages 74-75 of the IC-490 (9) -- May 19, 2003 issue.