Studies On Host And Migration Biotypes Of Aphis Gossypii Glover

The cotton aphid, Aphis gossypii Glover, is a worldwide and polyphagous pest. The host plants are more than 300 species in various botanical families, and it cause direct and indirect damage (virus transmission) for some economic crops and horticultural plants, such as cotton, cucurbits vegetable, flower and so on. The aphid species which had formed high specialization to one or two host plant, were found in some countries or regions, and some were formed host race. But the special host-biotypes of cotton aphid have not been identified in Nanjing, Jiangsu province. On the other hand, the cotton aphid is a kind of alternative host aphid species, which can migrate or spread between host plants or habitat in summer and autumn. So the migration may cause the change of diet spectrum. Now, the adaptation and the specialization of cotton aphid to host plants have not been studied, and their flight capacity and migration rule also been measured scarcely. So. it is valuable to study on the adaptation of cotton aphid to some crop plants and the migration behavior and capacity. In this paper, the selectivity and adaptation of cotton aphid to different host plants, the survival rate, reproduction capability, feeding behavior, the formation causes, flight capacity, population differentiation and heredity in flight were studied, and the results were summarized as follows:1. The host biotype of cotton aphidThe selectivity and orientation for host plant were studied by selecting method on single leaf or live plant, the results showed that the aphids originally feeding on cotton preferred cotton, summer squash and water melon leaves to cucumber and pumpkin leaves. While the aphids on the water-melon, pumpkin and cucumber had a preference for their original host plants to cotton leaves. The selecting rates of cotton aphid originally feeding on water melon, pumpkin and cucumber leaves to cotton leaves were 34.3%. 38.5% and 29.8%. respectively, but they were 53.8%. 52.1% and 56.9%, respectively on their original host plants. The alater aphids living on hibiscus preferred cotton plant greatly to cucumber. Few aphids was colonized on cucumber after transplanted 110 min and no offspring were reproduced during 24 h. The host plant of cucumber and cotton biotype aphids reared under laboratory conditions was exchanged between cotton and cucumber, and after exchanged 60min the aphids colonized were less than half. But 24 h after all aphids left and no offspring were found. So the fidelity of cotton aphid to cucumber or cotton plant was great.The strains of cotton and cucumber aphids were tested after rearing 1-3 years by comparing the adaptation of two biotypes to different host plants. The results showed that the specialization of the two host biotypes persisted very well. The cotton and cucumber strain could survive, reproduce offspring and build population on spring hibiscus, but the intrinsic increase rate of cotton strain was significant higher than that of cucumber strain. The pre-production period was longer of cucumber strain and the longest life-span was shorter than that of cotton strain. The cotton biotype aphids transplanted to cucumber or cucurit biotype aphids to cotton still could not survived and reproduced normally. The two bio-types could not established population on the egg-plant and amaranth plant. The cucurits biotype aphids could survive and reproduce on the cowpea and cucurits plants, but the cotton biotype aphids couldn't. The adaptation of cotton biotypes aphids to the cucumber plant or the cucurits biotype to cotton plant did not change when the cucumber or cotton was pre-damaged by cucurits or cotton biotype aphids, respectively. The aphids also could establish population on the pre-damaged host plant.The population characteristics of cotton aphid were studied by host transplantation method. The results showed that the transplanted cotton aphid and its offspring could survive 1 -4 and 1 -3 days, respectively, after transplanting among the cotton and cucurbits (cucumber, water melon and muskmelon)...