May June Beetle

Symptom

The caterpillars feed on all parts of the grapevine, including leaves and shoots. Their feeding activity usually begins in the evening, shortly after sunset, and continues throughout the night. Infestations are more severe during years with an early monsoon. The initial rainfall triggers rapid larval development, leading to heavy feeding damage. After pruning, vineyards are often observed to be densely covered with fresh shoots, which attract large numbers of larvae. When rainfall occurs during this period, caterpillar outbreaks typically appear the following night. The peak feeding activity takes place in the early hours of the night, when thousands of larvae gather in groups and cause extensive defoliation. Because the pest feeds mainly at night, it is difficult to control using conventional methods.