Feeding preferences of the Asiatic garden beetle

The Asiatic garden beetle (AGB), Maladera castanea, is an invasive scarab native to China and Japan. In the U.S., it is a pest of turfgrass, crops, and ornamentals. The larva, a white grub, damages roots as it feeds. The nocturnal adult beetle consumes foliage and blossoms, and has been minimally studied. Many traditional white grub controls have limited effectiveness against AGBs. A better understanding of adult habits, which influence larval location and adult damage, could suggest better management strategies, for example selecting plants less palatable to adult AGBs.

A field and a laboratory experiment were conducted to investigate AGB feeding preferences. The field experiment used beetle counts to indicate comparative preference for three cultivars each of nine edible plants: basil, beet, carrot, eggplant, kohlrabi, parsnip, hot pepper, sweet pepper, and turnip. AGBs were counted in a common garden with a randomized complete block design on six nights in July and August, 2012.

The laboratory experiment estimated concrete feeding preferences, using a no-choice format where change in mass and area of leaf pieces represented willingness to feed. Individual, starved beetles were each presented with one circular, 2.2 mm diameter leaf cutting for 48 hours. These tests included the basil, beet, and kohlrabi varieties in the field experiment, and six ornamental landscape plants: elderberry, viburnum, green ash, red maple, sugar maple, and American sweetgum.

The field experiment indicates a strong preference for basil, supported to a lesser extent by the lab experiment. Viburnum also appears to be favored.