Carrot Beetle: Pest Status and Bionomics on Cultivated Sunflower123

Abstract

Bothynus gibbosus (De Geer) is a serious pest of cultivated sunflowers in the High Plains area of Texas, It recently has destroyed small experimental plantings of sunflower in this area and has caused severe damage to the limited commercial acreage. Commercial production of the crop currently is not feasible in the High Plains, since measures are not available for control of the pest. Light-trap records showed 2 major seasonal population peaks which corresponded to emergence of over wintering adults in the spring and flight of 1st-generation adults. Damage to sunflowers by 1st-generation adults increased in late August. Sunflowers planted June 17 or earlier received less damage than sunflowers planted at a later date, hut even earlier plantings were damaged severely. Adults showed a preference to attack young immature plants. Adults of B. gibbosus entered plots of sunflower at night, burrowed to the plants’ root zone, and fed on the lateral roots at a mean depth in the soil of 355 cm. The adults left the soil after a mean period of 3.64 days following entry. An adult apparently will attack only 1 plant during the feeding period. Reproduction was not observed to occur in sunflower fields. Hibernating adults were found in early spring in a field of sunflowers that was not harvested the preceding fall. Response by B. gibbousus and plant damage was not different among 7 sunflower varieties and 1 hybrid tested in the field.