Interactions Between Diaphorina Citi Kuwayana And Its Two Species Of Host Plants

Morphology,bionomics and population dynamics of Diaphorina citri on its two species of host plants , tangerine (Citrus reticulata) and murraya (Murraya paniculata) , were comparatively studied. The biological activity of protection enzymes,detoxification enzymes and target enzymes in the pest were determined after the pest fed on tangerine and murraya. The susceptibility of the pest to two insecticides and the influence of different insecticides on enzyme activity of the pest feeding the two host plants were also researched. This paper also discussed the interactions among host plant, pest and insecticides. All the studies will lay theoretical foundation for the integrated control of Diaphorina citri and the breeding of the resistant varieties. The main results are as follows:1. The morphology and bionomics of Diaphorina citri on two host plantsMicroscopic observations and studies were conducted on the morphological characteristics of eggs, nymph and adult of Diaphorina citri and the mating,ovipositing,emerging , feeding and honeydew-secreting behavior of its adult, verifying some morphological characteristics and biological behavior of the pest. The female and male adults usually mated at noon and afternoon with strong sunlight,and the female laid their eggs after two to five days following mating. Unlike mating,the impact of sunlight on its oviposition was not obvious. The sooty diseases induced by Diaphorina citri feeding in lab occurred more easily and more seriously than in the open field.2. The population dynamics of Diaphorina citri on two host plantsThe overwintering adults began to damage aggregatively in mid-April,then from mid-April to the end of May and from early July to the end of September, 6 peaks of the adults occurred. Different host plants exerted significant effect on the generation durations of natural population of the pest and weak effect on the fecundity of natural population, but obvious influence on the growth, development and fecundity of Diaphorina citri lab population.3. Enzyme Activity of Diaphorina citri on two host plantsThe specific activity of the protective enzymes,GST and AChE of the 3rd nymph, the 5th nymph and adult of Diaphorina citri were tested after feeding on tangerine and murraya. The results indicated that different host plants had significantly influence on protective enzyme activities of Diaphorina citri;the effects on the GST activity of the nymphs was significant,but effects on adults was not;the effect on difference of the AChE activity between nymphs and adults was not significant.4. The sensitivity of Diaphorina citri to insecticides and GST activity on two host plantsWhen Diaphorina citri was treated with two kinds of insecticides,methomyl and quinalphos,the GST activity of the pest feeding on two host plants was significantly different. Methomyl obviously inhibited GST of Diaphorina citri on tangerine and with a strong inhibitory effect in low concentration of methomyl. At the beginning methomyl suppressed GST of Diaphorina citri on murraya,but in the late stage the GST activity obviously rose. Quinalphos displayed a clear induction effect on GST of Diaphorina citri on tangerine,and the higher the concentration,the stronger induction;but it presented an induction on GST of Diaphorina citri on murraya in low concentration,while high concentration of quinalphos showed an obvious inhibiting effect.5. Effect of Diaphorina citri feeding to some substances in two host plantsCompared with that in healthy leaves,the soluble protein contents of tangerine and murraya damaged by Diaphorina citri were significantly lower,tangerines decreasing 12.58% and murraya 10.33%;three protection enzymes in murraya,SOD,POD and CAT,activity decreased 13.07%,16.47%,and 1.94%,respectively,and the activity in tangerine fell 15.24%,19.06%,and 17.46%,respectively;Contents of non-enzymatic substances decreased at different levels, GSH and Vc in murraya significantly decreased 12.99% and 20.45%,especially the decrease of Vc was extremely remarkable,while in tangerine significantly dropped 14.65% and 16.41%;Contents of chlorophyll a,chlorophyll b,total chlorophyll and carotenoids also showed a decreasing tendency,they fell 14.26%,3.25%,13.36% and 10.12% in murraya,respectively,among them the decrease of chlorophyll a and carotenoids reached an significant level while chlorophyll b and total chlorophyll was not significant,while the four kinds of substances fell 13.44%,14.28%,13.59% and 9.76% in tangerine,respectively,among them chlorophyll a,total chlorophyll and carotenoids decreased extremely significantly , and chlorophyll significantly; Contents of MDA in murraya and tangerine significantly increaced 10.96% and 9.47%,respectively. All the data suggested that the effect of Diaphorina citri feeding on different host plants and the resistance of different host plants to Diaphorina citri are significantly different.