Integration Of Sterile Insect Technique And Egg Parasitization (Trichogramma Chilonis) For The Eco-friendly Management Of Helicoverpa Assulta (Lepidoptera: Noctuidae)

Oriental tobacco budworm (OTB), Helicoverpa assulta, is a serious pest of tobacco and vegetables in China, results in huge economic losses annually. In order to exploit new and effective environment friendly methods to control OTBs, sterile insect techniques were integrated with parasitoids (Trichogramma chilonis). The main results were as follows:1. Mass-rearing of insect pest is the pre-requisite for the sterile insect techniques (SIT). Applications of cell-unit techniques improved the efficiency and lowered the cost of production.2. Doses (⁶⁰Co-γ ray) ranging from 150 to 300Gy were applied to treat pupae of the OTBs, Helicoverpa assulta. There was no significant difference between treated and normal adults in flight distance, flight speed, adult longevity, mating ratio and mating number. However, the fecundity and egg hatching rate of irradiated adults decreased significantly. In F, generation, sex ratio (male: female), mortality rate and total development time increased. Adult longevity of F₁ adults reduced. When the pupae were treated with 150Gy, the egg hatching rate reduced significantly with the increase in overflowing rate of irradiated tobacco budworm in mating competition trials.3. Parasitization of treated and normal eggs of OTB by T. chilonis did not differ significantly. When the parasitoid rate was 0 % to normal eggs, parasitoid rate was still high on the treated eggs. At treatment of low doses (from 50mGy to 300mGy), there were no significant difference in the number of parasitoid per egg and female longevity. But the sex ratio (female: male) and parasitoid rate increased with the increase in radiation doses.4. T. chilonis was integated with different overflowing rate (OTBs were treated with dose 150Gy). The overflowing rate 6:1of OTB (treated: normal) resulted into high (88.40%) mortality of the host eggs if parasitoid was also applied in the trial.As the results illuminated that there was no significant difference in parasitization of T. chilonis between treated and normal eggs. The results may be attributed to the incomplete development of treated eggs that were therefore more suitable for the parasitoid. Based on the current studies, the synergistic effect from the integration of SIT and parasitoid can be successfully exploited for the environment friendly management of OTBs.