The Study Of The Food Chain Of "Cotton-Aphis Gossypii-Propylaea Japonica" And The Ecological Management On Cotton Aphid

The application of plant resistance has been an item of great concern for the scientific community. Plant resistance not only affected the development of herbivores, but also changes the composed and content of chemical substances in herbivores, witch indirect impacts the natural enemies by food chain. In this study, we carried a series of researches to study the system of "resistance cotton cultivar- Aphis gossypii-Propylaea japonica". The results as follows:1. Development and Reproduction of Propylaea japonica (Coleoptera: Coccinellidae) fed on Aphis gossypii (Homoptera: Aphididae)A laboratory experiment was designed to evaluate the effects of Bacillus thuringiensis (Berliner) Cry1Ab toxin on the survival, development and fecundity of predatory lady beetle, Propylaea japonica (Thunberg) through a food chain using cotton aphid, Aphis gossypii Glover as herbivore prey. No significant differences were observed in total survival from hatch to adult, in larval and pupal durations of Propylaea japonica (Thunberg) supplied with aphids fed on transgenic and nontransgenic cottons. Similarly, no significant differences in longevity, reproduction, weights and fatty acid contents of the adult beetles were detected. Our results suggested that transgenic cotton may not have any effects on survival, development and fecundity of P. japonica through food chain.2. Effect of cotton cultivar on development and reproduction of Aphis gossypi (Homoptera: Aphididae) and its predator Propylaea japonica (Coleoptera: Coccinellidae)The effects of three cotton cultivars with low ('ZMZ13'), medium ('HZ401'), and high gossypol content ('M9101') on the development, reproduction, and survival of Aphis gossypii and its predator, Propylaea japonica were investigated. Developmental duration and immature survivorship did not vary between aphids on the three cultivars. Whereas A. gossypii feeding on M9101 (high gossypol cultivar) displayed significantly shorter adult longevity and lower fecundity than aphids fed on 'ZMS13' and 'HZ401'. Free fatty acid content in cotton aphids reared on 'M910F was greater than in those reared on 'HZ401' and 'ZMS13'. No significant differences in survival and lifetime fecundity of P. japonica were observed between P. japonica fed cotton aphids reared on the three different cultivars. P. japonica fed aphids from 'M9101' showed a significantly shorter developmental period and greater adult weight than those fed aphids from the other twocultivars. The decreased larval developmental duration and increased adult weight of P. japonica fed cotton aphids reared on the high gossypol-containing cultivar might have been caused by the high fatty acid content of the prey aphids. Our results indicate that high gossypol in host plant had an antibiotic effect on A. gossypii and showed a positive effect on growth and development of P. Japonica at the third trophic level. This suggests compatibility between one form of host plant resistance and biological control by predators. The allelochemical contents should be taken into account in integrated pest management for their effects on both herbivores and entomophagous insects.3. Searching and foraging behavior of Propylaea japonica (Coleoptera: Coccinellidae) towards Aphis gossypii (Coleoptera: Coccinellidae) on the CottonThe studied on the searching and foraging behavior of Propylaea japonica towards Aphis gossypii, when the aphids were different densities, different spatial distribution and from different cotton on the cotton, the result show: the searching of Propylaea japonica on cotton aphid changed down gradually when aphid densities from low to high. The searching and foraging trended to the top of the cotton, Propylaea japonica will be fond of searching and foraging aphids on the top of cotton when cotton aphids was at a certain density, preyed a few cotton aphids on the middle part, and preyed few on the bottom part. The predation of Propylaea japonica has no difference on different part of cotton to aphids from different cotton, the searching times of Propylaea japonica descended when it preyed mostly on aphids from cotton M9101 than another treatment.4. Predation ofPropylaea japonica (Coleoptera: Coccinellidae) on aphid from different cotton cultivarsThe predation of Propylaea japonica adult on Aphis gossypii Glover reared on 3 different cotton cultivars with low gossypol content (ZMS13), middle gossypol content (HZ401) and high gossypol content (M9101) was investigated. Preying capacity of adult P. japonica fed aphis from cotton with different gossypol on aphids from same gossypol cotton cultivar was significant greater than aphid from other cotton cultivar treatments. Adult ladybirds prefer to predation aphid from high gossypol cotton cultivar. No significant differences of preying capacity of adult P . japonica to cotton aphid when development with aphids from different cotton. There was interaction response of two factors of different ladybirds type and aphids from different cotton. Our result clearly...