EFFECT OF IRRADIATION ON DEVELOPMENT AND PROPAGATION OF LARCH BARK BEETLE（Coleoptera：Scolytoidea）

The developing stages of larvae,pupae and adult of the Larch Bark Beetle(Ips subelongatus Mots.),which was rearing on the fresh trunk of the Prince Ruppricht's Larch in laboratory after collecting from Weichang County,Hebei province,were irradiated by 60Co γ-rays or X-rays(9MeV),and the irradiation impact on the development and propagation was investigated through continuous rearing.There were adults emerged from the irradiated trunks and F1 generation larvae founded in new trunks when the trunks contains all the larvae stage of I.subelongatus and irradiated at the dose of 20 to 60Gy.But there were no F1 generation larvae founded while irradiated over 80Gy;While the trunks contains most pupae and newly developed adults and then irradiated,adults and F1 larvae could develop at the dose of 20 to 100Gy,but no F1 larvae developed when the dose was higher than 120Gy.According to results of adults irradiated by X-rays,F1 larvae or adults developed after irradiation of 40 to 120Gy,and no F1 larvae found in the treatments of the dose higher than 140Gy.Thus,the sterile doses which could prevent F1 larvae emergence be set as 80Gy for larvae,120Gy for pupae,and 140Gy for adults,respectively,and which could be used as effective dose for the quarantine treatment of imported timber.