EFFECTS OF CEROTOMA ARCUATA (COLEOPTERA, CHRYSOMELIDAE) ON PREDATION OF NODULES AND ON N-2 FIXATION OF PHASEOLUS-VULGARIS

Damage by Cerotoma arcuate Olivier to Phaseolus vulgaris L. grown in t he greenhouse was evaluated. In 1 experiment, the addition of 2 or 4 p airs of adult C. arcuata at the Ist or end trifoliate growth stage res ulted in approximate to 50% losses in seed yields. By using physical b arriers in a 2nd experiment, the effect of adult feeding on leaves was separated from the effect of larval feeding on nodules and root in th e soil. When C. arcuata larvae were given access to roots and nodules, 2 pairs of adults were sufficient to decrease the numbers, dry weight s and activity of the nodules formed, causing a reduction in yield. Th ere was no decrease in nodulation or yield when access of larvae to th e nodules was impeded. The decrease in N-2 fixation caused by consumpt ion of nodules by C. arcuata larvae was more deleterious to plant grow th and yield than the defoliation imposed by the adults.