NATURAL PEST RESISTANCE OF PRUNUS TAXA TO FEEDING BY ADULT JAPANESE-BEETLES - ROLE OF ENDOGENOUS ALLELOCHEMICALS IN HOST-PLANT RESISTANCE

Feeding intensity of adult Japanese beetle (Popillia Japonica Newm.) w as compared among 27 taxa of Prunus host plants during 24-hour no-choi ce feeding trials conducted on individual leaves. Fecal dry mass per b eetle, a measure of feeding intensity, varied from 0 mg.d(-1) for Prun us padus L. to 20.4 mg.d(-1) for P. sargentii Rehd, and P. tomentosa T hunb. Prunus padus, P. laurocerasus L., P. mahaleb L., P. serotia Ehrh ., P. virginiana L., P. americana Marsh., P. xyedoensis Matsum., and P . besseyi Bailey were resistant based on feeding intensities of <4.3 m g.d(-1) (levels not significantly different from zero), Feeding intens ity decreased exponentially as endogenous foliar cyanide potential inc reased. Evaluation of the cyanogenic glucoside prunasin in artificial diets showed a similar relationship with feeding being reduced by 50% (ED,,) at 4.9 mmol.kg(-1) in the diet. Prunus mahaleb was highly resis tant to Japanese beetles despite having low cyanide potential, Two cou marin compounds known to exist in P. mahaleb, herniarin acid coumarin, mere tested in artificial diets and mere effective feeding deterrents with ED50 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 resistanc e to this pest.