Study On The Inter-species Competition Of Aphis Gossypii Glover And Tetranychus Cinnabarinus In Transgenic Cotton Field

With the large scale cultivation of transgenic insect-resistant cotton in Xinjiang,cotton bollworm is not the major pest of cotton any more.The number of piercing-sucking insects,such as cotton aphids and cotton mites,is increasing year by year,causing serious losses to Xinjiang cotton production.There is a fierce inter-species competition of replacement between cotton aphids and cotton leaf mites in the transgenic cotton,this kind of competition will not appear in the same area or the same cotton field at the same time as serious phenomenon.This paper focus on studying the function of cotton aphid and cotton leaf mite’s growth trend,the proportion of the initial competition,the sensitivity difference of chemical pesticides during the competition to replace process,with the clue of inter-species competition between cotton aphid and cotton leaf mites and the metabolites of transgenic cotton as the starting point,thus it can reveal the ecological mechanism of cotton aphid and cotton leaf mite on insect-resistant cotton.1.Studies on the inter-species competition between Tetranychus truncatus Ehara and Tetranychus urticae showed that the population growth rate of the mixed population was higher than that of the single species,the population growth rate of the mixed population of Tetranychus truncatus Ehara is less than its individual population,and its innate capacity of increase（rm）is 0.0474.For Tetranychus urticae,its innate capacity of increase（rm）is 0.0793.The growth rate of SOD,POD and CAT,these three protective enzymes in Tetranychus urticae were higher than that of the Tetranychus truncatus Ehara before and after competition.Tetranychus urticae has a stronger ability to compete.2.The chlorophyll content of cotton aphids and cotton leaf mites has significantly decreased after feeding on cotton leaves,and the chlorophyll reduction of mixed populations was between the them.The soluble sugar content of cotton aphid has decreased significantly since feeding on cotton leave,but the soluble sugar content of cotton leave mites has increased.The content of soluble protein has increased after cotton aphid feeding on cotton leaves,the soluble protein of cotton leaf mites decreased and the protein content of mixed population changed little.3.Aphis gossypii Glover and Tetranychus cinnabarinus in cotton leaves after feeding in cotton defense enzymes（CAT,POD,PPO,LOX）changed the activity,the first of the cotton leaf mite make defensive reaction then a mixed population,finally the aphid population;induced defense enzyme is the largest mixed population is at least the aphid population.The growth rate of SOD,POD and CAT,these three protective enzymes in Aphis gossypii Gloverwere higher than that of the Tetranychus cinnabarinus before and after competition.Aphis gossypii Glover has a stronger ability to compete.4.The population with the damage-first and the dominant initial density will be at an advantage in the competition.The opposite will at a disadvantage.And two population with same density will interfere with each other,which may affect each population quantity.5.The population of cotton aphid will rapidly increase at 20 ℃,and the population of cotton leaf mite will be inhibited.At 34 ℃,the population of cotton leaf mite will increase rapidly,while the population of cotton aphid will be inhibited.When it is 26 ℃,both population won’t change a lot.6.The effect of aphid on the fecundity of spider mites shows that a small amount of cotton aphid has a promoting effect on the amount of spawned egg of cotton leaf mite.When the number of cotton aphid has increased,they will have inhibitory effect on cotton leaf mite.The study of cotton leaf mite’s effect on cotton aphid’s amount of spawned egg shows that few cotton leaf mite will have a promoting effect on cotton aphid’s amount of spawned egg.Although the increase of cotton leaf mite population will have inhibitory effect on the increase of population of cotton aphid,but the impact will not be that obvious.7.After being sprayed by LD₅₀,the number of cotton aphid population has been increasing,while the number of cotton leaf mite population and the control group didn’t change.After dealing with the LD₅₀,the initial density of cotton aphid won’t have inhibitory effect to the number of cotton leaf mite population,instead,it will increase because of the decrease of the number of cotton aphid population.