The Diurnal Flight Activities And Tropism Of Two Thrips To Host Volatile Compounds

Western flower thrips, Frankliniella occidentalis Pergande is an invasive alien specie found in China recently, and it is one of the most dangerous pests in 4500 thrips. Onion thrips, Thrips tabaci Lindeman is an important pest on onion and garlic damaged plants in all regions of our country.They cause of injury to the main marketable parts of plants, leaves, flowers and fruits, and also could transmit tomato spotted wilt virus (TSWV).The crops infested can not grow and yield losses recorded on vegetables, flowers and fruit attacked by thrips increase year by year. Therefore, the behavioral responses of thrips to host volatile compounds were examined in a controlled environment, then the effects of key volatile chemicals on the sticky cards were explored in a greenhouse and a efficient attractive card to thrips were developed. In addition, thrips'daily flights were monitored in greenhouse and the influences of 4 factors on flight activity of thrips were determined in a laboratory-controlled environment. The major results are listed as follows:The daily flight activities of thrips were examined in the greenhouse. It was found that the flight activities of western flower thrips were just the same at there different weathers, and the flying thrips were most abundant between hours 08:00–10:00, declined at mid-day, then slightly increased during hours 14:00–16:00, however they decreased to a very low level at 18:00. The use of light traps showed no thrips flight activity during the night. The total number of thrips that flew onto cards on rainy or cloudy days was higher than that on sunny days. The flight activities of onion thrips were as same as the western flower thrips. The daily flight curve also indistinctly kept two peaks during 08:00-10:00 and 14:00-16:00, but flying thrips were more abundant between hours 14:00-16:00 in sunny days and less in rainy day or cloudy days.Under laboratory controlled conditions, thrip flight activity was highest under light intensity between 4 000 and 6 000 lux, air temperature of 27oC, and RH of 70%. In addition, starved thrips flew more readily than non-starved thrips.Effect of different plants leaves, extractions and volatile compounds on the behavior of the adult thrips were tested with a Y-tube olfactometer. It was found that different behavior of thrips to different plants leaves. White radish and cabbage have significant attraction for F.occidentalis. The effect of celery, chili, eggplant, tomato and carrot on the behavior of thrips was no significant to the control. Cherry tomato leaves have some repellent action to adult thrips, but there was no significant difference. The extractions of plants leaves have obvious temping function to the adult thrips, and the order from high to low is eggplant≥cherry tomato≥tomato≥carrot≥cabbage≥bean≥chili. The extrations of white radish leaves have obvious repellent effect to the thrips, and the cucumber leaves have no significant action. The volatile chemicals have the different effect to the adult thrips, even a same compound at different concentration has different action. The compound B and B+G have the significant attraction for thrips at concentration 10% and 1%. The best colour was yellow, the best combination method of attractant and card was direct painting, the best Control release agent was CR01, the best attractant was compound B, the best concentration was 10%. The average total numbers of western flower thrips and onion thrips caught by the best attractive cards was about 7.6 and 10.5 times more than the sticky cards. The best attractive cards was not only more attractive than common sticky cards, but also added Control release agents for long lasting and less effective attractant, which reduce the cost of the attractive card and make its promotion and application more easily.