Natural Pest Resistance of Prunus Taxa to Feeding by Adult Japanese Beetles: Role of Endogenous Allelochemicals in Host Plant Resistance

Abstract

Feeding intensity of adult Japanese beetle ( Popillia japonica Newm.) was compared among 27 taxa of Prunus host plants during 24-hour no-choice feeding trials conducted on individual leaves. Fecal dry mass per beetle, a measure of feeding intensity, varied from 0 mg·d -1 for Prunus padus L. to 20.4 mg·d -1 for P. sargentii Rehd. and P. tomentosa Thunb. Prunus padus, P. laurocerasus L., P. mahaleb L., P. serotina Ehrh., P. virginiana L., P. americana Marsh., P. ×yedoensis Matsum., and P. besseyi Bailey were resistant based on feeding intensities of <4.3 mg·d -1 (levels not significantly different from zero). Feeding intensity decreased exponentially as endogenous foliar cyanide potential increased. Evaluation of the cyanogenic glucoside prunasin in artificial diets showed a similar relationship with feeding being reduced by 50% (ED 50 ) at 4.9 mmol·kg -1 in the diet. Prunus mahaleb was highly resistant to Japanese beetles despite having low cyanide potential. Two coumarin compounds known to exist in P. mahaleb , herniarin and coumarin, were tested in artificial diets and were effective feeding deterrents with ED 50 values of 5.9 and 2.5 mmol·kg -1 in the diet, respectively. This research demonstrated a wide range of host plant resistance to feeding by adult Japanese beetles and further indicates that prunasin, herniarin, and coumarin are important factors in host plant resistance to this pest.