Lipid, polyamide, and flavonol phagostimulants for adult western corn rootworm from sunflower (Helianthus annuus L.) pollen

Adult Diabroticites including western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, consume pollen of corn, squash, sunflower, and other species. Short-chain neutral amino acids in methanol-water extracts of pollen have been previously identified in our laboratory as strong phagostimulants for Diabrotica. Bioassay-driven fractionation was used to characterize the interacting lipid and midpolarity phagostimulants for adult WCR in Giant Gray Stripe sunflower, Helianthus annuus L., pollen. Lipids rich in omega 3-linolenic acid including triglycerides, free fatty acids, phosphatidylethanolamines, phosphatidic acids, and phosphatidylcholines were highly phagostimulatory. Other important phagostimulatory components included a hydroxycinnamic acid-polyamine amide, N-1,N-5,N-10-tri[(E)-p-coumaroyl]spermidine and a flavonol, quercetin beta-3-O-glucoside. The structural characteristics of these phagoactive compounds and their role in the pollinivory specialization of rootworm beetles are discussed.