| Laodelphax striatellus(Fallen)is a kind of important rice pest,which does harm to rice plants through piercing and sucking,and also is the carrier of Rice stripe virus(RSV),causing severely affection to rice production.Up to now,the chemical insecticide is still the main method to control L.striatellus,while many studies have shown that applications of some pesticides could induce the resistance and resurgence of L.striatellus.Previous study about inducing resistances of L.striatellus are mainly concentrated on insect itself,whlie few researches related to how pesticide affects L.striatellus on transmitting RSV.The impact of triazophos and validamycin on experimental population growth of L.striatellus with RSV and without RSV,and the transmission virus rate of L.Striatellus were investigated in this study.The results are as follows:(1)With the soaking seedling method,the sensitivity of triazophos to L.striatellus with and without RSV was tested.The results showed that L.striatellus in the 3rd instar nymphs without RSV was more sensitive to pesticides than those with RSV.Treated nymphs without RSV with triazophos for 72 hours,the LC10,LC20 and LC30 is 2.14mg·L-1,5.73mg·L-1 and 11.65mg·L-1,respectively;Treated nymphs with RSV with triazophos for 72 hours,the LCio,LC20 and LC30 is respectively 6.24mg·L-1,13.41mg·L-1 and 23.30mg·L-1,respectively.The effective fecundity of L.striatellus with and without RSV treated with triazophos and validamycin has increased,L.striatellus treated with triazophos increased more remarkably.Additionally,treated with validamycin at 200mg L-1 and triazophos at LC20 concentration caused the most significant impact on the population growth of L.striatellus.(2)With the soaking seedling method,the changes of vertical transmission and horizontal transmission treated with triazophos at LC20 and validamycin at 200mg·L-1 to L.striatellus with and without RSV were studied.The results showed that the viruliferous percent of the offspring of L.striatellus with RSV has significantly increased with the treatment of triazophos.The toxicant transmitting capacity on rice seedling of second generation of L.striatellus with RSV treated with two pesticides did not changed statistically significant.However,the acquired insects of L.striatellus without RSV to rice seedlings with RSV significantly improved after treated with validamycin 200mg·L-1,while there was no significant difference in triazophos.The results indicated that triazophos and validamycin could affect the propagation velocity of RSV between L.striatellus and host plants.(3)With the method of electrical penetration graph(EPG),changes of feeding behavior of L.striatellus without RSV treated with validamycin at 200mg·L-1 were assayed.The results showed that,after treated with validamycin,the time((0.71±1.85)min)of L.striatellus nymphs without RSV spend on xylem was significantly lower than those in control group,and the time((145.22±12.17)min)of nymphs salivating increased by 16%,and also increased in ingestion in the phloem((212.36±22.83)min);The time((0.31±0.60)min)of L.striatellus adult female without RSV spend on the phloem was significantly lower than those in control group,and the time((136.65±12.51)min)of that nymphs salivating,the time((277.99±23.72)min)for ingestion in the phloem is no significant difference with the control group.The results showed that the increasing of acquired insects of L.striatellus without RSV caused by validamycin was not significantly associated with its feeding behavior. |
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