Population Dynamics Of Aphis Gossypii On Prickly Ash And Effect Of Prickly Ash Coumarin On Biochemical Characteristics Of Aphis Gossypii

The main production base of Green Prickley ash in China is Chongqing,of which planting area has already amount to 760,000 mu.However,with the continuous development of Prickley ash production,the harms of pests and diseases are prone to be more and more serious,especially,Aphis gossypii.In this study,we investigated the annual population dynamics of Aphis gossypii in Prickly ash orchard,the growth-and-development of Aphis gossypii on Prickley ash under different temperatures and the resistance of secondary metabolites from Prickly ash to Aphis gossypii. Forthmore,we analyzed the effect of Prickly ash coumarin on the sugar invert enzymes and detoxification enzymes of Aphis gossypii.The main results were as follows:1.The natural population dynamics of Aphis gossypiiSystematic investigations were carried out on the dynamics of natural population of Aphis gossypii in Prickly ash orchard.The result indicated that the population quantity of the insect was obviously increased from the early May to the late June,then decreased till September,and increased again,the densities of adult and larva at the position in South direction were markedly higher than other directions.Spatial distribution information showed that the population was uniform pattern during the winter,but aggregate pattern at other times,the individual group was 4.5 per leaf,and the aphid population traded off during the growth period of Prickly ash.The most suitable theoretical sampling quantity at different densities and the sequential sampling model were presented:T_n= 5n±4.5709n^1/2(Spring Aphids),T_n= 50n±24.8412n^1/2(Summer Aphids),n was the sequential sampling quantity.2.The influence of temperature on the growth-and-development of Aphis gossypiiAnalyzing the survival rate,mean longevity and fecundity of Aphis gossypii on Prickley ash at 6 constant temperatures 14℃,18℃,21℃,24℃,27℃and 30℃,we found:At 14℃,the survival rate of larva and the reproduction rate of adult were 66.94%and 13.5687 respecively,the reproductive rate(R₀).the intrinsic rate of increase(r_m)and the finite rate of increase(λ)were the lowest.At 18℃,the mean longevity of adult was the longest,and the date of maxiun mortality was the latest among these six temperatures.As the temperature increasing,the date of maxiun mortality was advanced,the shortest date of maxiun mortality was 5.28d at 30℃.At 18℃～21℃,the fecundities of cotton aphid were the highest on Prickley ash,and the reproduction quantities per female were 35.8216 and 35.0802 respecively.The survival rate of larva(92.33%and 90.14%)at 21℃and 24℃were significantly greater than those at other temperatures.The developmental duration was shortened at high temperature(27～30℃),but r_m increased significantly at 30℃ (0.3364),which implied that high temperature can cause the population increasing observably in short times.According to R₀,21.7℃was considered to be the most suitable temperature for Aphis gossypii.3.The anti-cotton aphid fiction of secondary metabolites from prickly ashBy using the artificial rearing technique of aphids,we evaluated the resistance of a-pinene,β-pinene and coumarin from prickly ash to Aphis gossypii.The result suggested that they all had anti-cotton aphid action.Among the three kinds of secondary metabolites,theβ-pinene's resistance was the weakest.The a-pinene had strong repellent and antifeed action when its concentration was low(0.015%to 0.045%),while the concentration increased to 0.060%,the anti-cotton aphid action of a-pinene decreased on the contrary.Resistance of coumarin to Aphis gossypii was not obvious in low concentration,but in high concentration(＞0.060%)the resistance increased significantly, mainly represented toxic effects.4.The influence of prickly ash coumarin to the sugar invert enzymes of Aphis gossypiiTo further understand resistant mechanism of prickly ash coumarin to aphid,the activities of sugar invert enzymes of Aphis gossypii were detected with microtiter plate reader after adding different dosage of coumarin.The result showed there was no marked difference in the activities of amylase,sucrase and trehalase.It indicated that coumarin had not obvious effect on the transition of sugar and energy of Aphis gossypii.5.The influence of prickly ash coumarin to the detoxification enzymes of Aphis gossypiiThe impact of coumarin on the activity of carboxylesterase(CarE),acid phosphatase(ACP), alkaline phosphatase(ALP)and glutathione S-transferase(GST)in Aphis gossypii was measured. The result revealed that coumarin strongly inhibited the activity of CarE when its concentration was 0.06%,the inhibition rate was 52.55%,but the inhibition decreased when its concentration incresed. The inhibition of coumarin to ACP and ALP was not great,and the activities all decreased as the concentration of coumarin increased.The inhibition of coumarin to GST was the strongest of all,the inhibition rate was 31.1%when its concentration was 0.02%,and the inhibition rate was the highest (78.76%)when its concentration was 0.1%.The results implied that coumarin could reduce the antidotal ability of Aphis gossypii by inhibiting the activity of detoxification enzymes.