A feeding deterrent from Persicaria lapathifolia (Polygonaceae) leaves to larvae of Gallerucida bifasciata (Coleoptera: Chrysomelidae)

Among three species of polygonaceous feeding leaf beetle, Galerucella grisescens, Gallerucida bifasciata, and Gastrophysa atrocyanea, only Gall. bifasciata did not use a polygonaceous plant, Persicaria lapathifolia, as a food. 2nd and 3rd instar larvae and adults of Gall. bifasciata fed on the leaves, however, the feeding amount decreased day by day and all died. The 1st instar larvae hardly fed on the leaves and all larvae died. Biological tests and chemical analysis revealed that feeding deterrents were present in P. lapathifolia leaves. A feeding deterrent was isolated and identified as 3-hydroxy-5-methoxy-6,7-methylenedioxy flavanone. The compound deterred 1st instar larvae of Gall. bifaciata from feeding and significantly lessened the survival rate of the larvae at concentrations higher than 1.0 mg/ml. Larvae of Gal. grisescens were not deterred from feeding by the compound at the concentration of 5 mg/ml. The presence of other fractions increased the feeding deterrent activity of the compound to 1st instar larvae of Gall. bifasciata. These results revealed that P. lapathifolia leaves contain multiple feeding deterrents to Gall. bifasciata.