Study On The Dynamic Characteristic Of Aphis Gossypii And Natrual Enemies In Different Irrigated Ways And Nitrogen Fetilizer Levels

A systematic investigation was made of the dynamic characteristic of Aphis gossypii and natural enemies in different irrigated ways between furrow and drip irrigation , the different irrigation quota and different periods of irrigation with the same irrigation quota under the conditions of drip irrigation., and nitrogen fertilizer quota under the conditions of drip irrigation.The results showed: during the cotton bugs stage, the occurrence degree of A. gossypii under mulched drip irrigation was lighter than the normal furrows irrigation method, the difference is significant. The occurrence degree of A. gossypii was different during different irrigation quota, the low water quantity was favorable to the occurrence of A. gossypii, but the higher water quantity wasn't, both of these have significant difference to the normal dripping area. There was also not significant difference to the occurrence of aphis between advanced one week for irrigation to pushing one week for irrigation based on the middle irrigation quota in budding stage. The dynamic characteristic of winged aphid in different irrigated ways didn't have the same way, but the differences were not significant.The results of experiment showed:the different levels of nitrogen application have an effect to the occurrence low of the aphis. More nitrogen is helpful to the occurrence of the aphis in budding and flowering boll period, but the difference is not significant. The difference between the low and high nitrogen was the biggest, the difference is significant. The winged aphis also have no significant difference in all nitrogen area.The grey system analysis on dominant natural enemies influencing A. gosspyii population showed that: nature enemies have different influence to the cotton aphis in different treatment area. During the normal irrigation ,low irrigation quota and to pushing one week for irrigation based on the middle irrigation quota in budding stage, parasitoids has the most influence to the aphis, next is lady beetles,the third is green lacewings; but in the advancing one week for irrigation based on the middle irrigation quota in budding stage, green lacewings has the most influence to the aphis, next is parasitoids ,the third is lady beetles; on the middle irrigation quota in budding stage, parasitoids have the most influence to the aphis, next is green lacewings, the third is lady beetles; on the high irrigation quota, lady beetle is the fist, next is green lacewings, the third is parasitoids; on the low and middle nitrogen fertilizer region, green lacewings has the most influence to the aphis, next is lady beetle, the third is parasitoids; on the high nitrogen fertilizer region, lady beetles has the most to the aphis, next is parasitoids, the third is green lacewings.Correlation analyses revealed that, The natural enemies have different influences to the aphis in different treatment regions. The lady beetles had the highest correction to the aphis with significant differences in all regions, was the main enemies to the aphis. The correction between green lacewings and the aphis has significant differences among the high-water region, the low nitrogen and high nitrogen regions. The influence between parasitoids and the aphis has a significant difference in furrow region and the low-water drip region, but in other regions was not significance.