Biology On Different Tree Species And Cold Hardiness Of Hyphantria Cunea Drury

The fall webworm, Hyphantria cunea Drury (Lepidoptera: Arctidae) is a worldwide insect pest that had caused large lost in its distribution area over the world. It broke out in many provinces and was becoming a dangerous insect pest in forest and garden in China. This paper mainly dealt in details with the effects of host plants and larval density on the development and production, and the pupal cold-hardiness of H. cunea. The main results were summarized as follows:1 The effects of host plants on the basic biology of the experimental population of Hyphantria cuneaHost plants had different effects on the fall webworm. The results were: H. cunea could not complete its life cycle on pagoda tree, but could do on the other three plants. There were different effects of host plants on the breadth of larval head capsule. The choice trials showed that the order of adult oviposition preference on different host plants was chinar>mulberry>willow>pagoda tree, and the order of distribution of newly hatched larvae was mulberry>chinar>willow>pagoda tree. The larval duration sequence was willow>chinar>mulberry. The ratio of pupation and mating were mulberry>chinar>willow. The adult fecundity sequence was chinar>mulberry>willow. The supercooling point (SCP) and freezing point (FP) of the pupae reared from willow were significantly higher than that from the other tested plants; the pupae reared from mulberry and chinar have no difference in SCP and FP.2 The effects of host plants on basic biology of the natural population of Hyphantria cuneaHost plants had different effects on the fall webworm. The results were: H. cunea could not complete its life cycle on pagoda tree, but could do on the other plants. The choice trials showed that the order of adult oviposition preference on different host plants was velvet ash >chinar>mulberry>willow>purple-leaf plum>pagoda tree, and the order of distribution of newly hatched larvae was mulberry>willow>chinar>velvet ash>purple-leaf plum>pagoda tree. The larval duration sequence was mulberrymulberry>velvet ash>willow>purple-leaf plum. The pupae reared from different host plants have no difference in SCP and FP.3 The effects of larval hunger on development and reproduction of Hyphantria cuneaCompared with the contrast, the hunger treatment in the 2nd instar larvae had no significant effects on the development and reproduction of H. cunea. The hunger treatment in the 4th instar larvae showed that: the longer the hungry time, the higher the larval mortality , the longer the duration of larval stage and the lower the ratio of pupation, eclosion, and the fecundity. The hunger treatment in the 6th instar larvae had obvious effects on the development and fecundity of the fall webworm. The larval duration after the hungry treatment was significantly longer than the contrast, and about 34.17% and 71.67% of the larvae advanced their pupation after 8d and 12d hungry treatment, respectively. The ratio of the treated larval survival, eclosion, mating and the fecundity were significantly lower than that of the contrast.4 The effects of larval densities on development and reproduction of Hyphantria cuneaBoth the low (1, 5, 10 larvae) and high (60 larvae) larval density had the adverse effects on the development and reproduction of H. cunea. The survival rate reared at the densities of 30 larvae was the highest among the tested larval densities and the larval duration was the shortest. All of the larvae singly reared were died before the 4th instar larval stage. The ratio of pupation, eclosion, mating and the fecundity reared at the larval density of 5 and 10 were significantly lower than that at the laval density of 30 and 60. There were no significant differences in the ratio of pupation, eclosion, mating and the fecundity reared at the larval density of 30 and 60.5 The cold-hardiness of the overwintering pupae of Hyphantria cunea Experiments were carried out to examine the capability of the pupal cold-hardiness during the overwintering period. The results showed that the cold-hardiness of the female and male pupae gradually strengthened with the winter temperature decreasing and weakened with the temperature increasing in the spring. The SCP and the FP of the female and male pupae changed greatly in the different overwintering periods. The SCPs of the over-wintering female and male pupae during the pre- and mid- over-wintering period were significantly lower than that of other periods. Both the water and the fat content in the pupae at the mid- over-wintering period were significantly higher than that of other periods. The analysis showed that both the water content and the total fat had negative correlation with the SCP of the female and male pupae (P<0.05).