Flavonol glycosides from four pine species that inhibit early instar gypsy moth (Lepidoptera: Lymantriidae) development

Abstract

Early instars of gypsy moth (Lymantria dispar L.) generally do not feed on pine (Pinus) species, perhaps due to secondary compounds found in pines. To test this hypothesis, ethanolic extracts from jack pine (Pinus banksiana Lamb), red pine (Pinus resinosa Ait.), scotch pine (Pinus sylvestris L.) and white pine (Pinus strobus L.) (Pinaceae) needles were prepared. Extracts from all four pine species, when incorporated into artificial diet, significantly reduced weight and increased mortality for 2nd instars. A purified ethanolic fraction from jack pine (fractionated on a polyvinylpolypyrrolidine (PVPP) column with a 100% water to 100% ethanol gradient), containing phenolics and flavonol glycosides significantly reduced growth and increased mortality of gypsy moth 2nd instars. Eight flavonol glycosides were isolated from the four pine species, two of which (rutin and quercetin-3-0-glucoside) were common to all four species. These two compounds, and the aglycone quercetin, when incorporated into diet, significantly reduced growth of gypsy moth 2nd instars. These results suggest that early instars of gypsy moth are sensitive to pine flavonols, and the presence of these compounds may be one reason they do not generally feed on pines until later instars.