Host plant feeding preferences of the Asiatic garden beetle

The Asiatic garden beetle (AGB), Maladera castanea, is an invasive scarab pest of turfgrass, crops, and ornamentals. The beetle has been minimally studied, and is resistant to many traditional controls. 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.

Field and laboratory experiments were conducted to investigate AGB feeding preferences. The field experiments 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 in 2011 and 2012.

The laboratory experiments estimated concrete feeding preferences, using a no-choice format where change in mass and area of leaf pieces represented willingness to feed. These tests included the basil, beet, and kohlrabi varieties used in the field experiments, and, in 2012, also included six ornamental landscape plants: elderberry, viburnum, green ash, red maple, sugar maple, and American sweetgum.

The 2011 and 2012 field experiments indicated a strong preference for basil over other crop plants. This was supported by the 2012 lab leaf area change data. Statistically significant differences were not discernable among other edible plant varieties. The 2012 laboratory no-choice tests indicated that sugar maple was significantly less likely to be eaten than the other landscape plants tested, which were not significantly different from one another in terms of AGB feeding.