Larix gmelinii monoterpene volatiles from slow-release micro-capsules affecting host selection behavior of Dendrolimus superans

Plant terpene volatiles with many monoterpenes are highly volatile and can influence insect behaviors. In order to control the release of such active volatile compounds, and to maintain a certain active duration, three major Larix gmelinii needle related volatiles -pinene, myrcene and camphene were respectively formulated into slow-release microcapsules. The microcapsule suspension of each volatile compound was spayed onto 2-year-old L. gmelinii seedlings in comparison with those spayed with the corresponding solutions made straight from the volatile compounds. The attraction and oviposition behaviors of Dendrolimus superans female adults to and on these volatile treated larch seedlings were studied in an indoor Y-tube olfactometer and an outdoor caging bioassay, respectively, at each day for five days. Our results from lab Y-tube bioassay showed that -pinene at 1 L/mL and myrcene at 1 L/ mL from the solutions were significantly attractive to D. superans female adults (P 0.01) at day one. Seedlings sprayed with the slow-release microcapsule suspensions also showed significant attraction to D. superans female adults for four days. Camphene at 2 L/mL from the synthetic solution showed significant repellency(P 0.01) at day one, and seedlings sprayed with the slow-release microcapsule suspension also showed significant repellency effect for four days. The outdoor caging bioassays showed that microcapsule suspensions of -pinene and myrcene significantly increased female oviposition(number of eggs) whilst the microcapsule suspension of camphene significantly reduced the number of eggs laid on treated seedlings. These effects lasted for three days. Our data suggest that microcapsule of these highly volatile compounds such as monoterpenes with chitosan may provide a feasible control release formulation to extend their effective life-span (duration).