| In recent years,Shandong Province has become an important tea producing area in China,which has created more economic benefits,but Aleurocanthus spiniferus Quaintance was a kind of piercing-sucking mouthpart insects in tea plantations and had seriously restricted the development of tea industry.At present,in order to achieve the control effect,chemical pesticides were sprayed on tea leaves,this method was quick effect,but farmers usually only used several kinds of insecticides,reduced the effect on the pests,that caused farmers increase the dosage and the spraying times,which resulted in the increase of pesticide residues and environmental risk problems,and against the sustainable development policy.This study has screened out high toxicity chemicals for A.spiniferus nymphs from 16 kinds of common or new pesticides;and the field experiments were carried out to clear and definite the efficiency of insecticides;while the residue of 6 kinds of insecticides were studied,the Gas Chromatography-Mass Spectrometry（GC-MS/MS）method for the detection of 6 insecticides in tea was established,and the residual quantity of7d,14d and 21d after the insecticides applied was determined;and determined the toxicity of 6 insecticides on natural enemies Coccinella septempunctata.The main results are as follows:1.The toxicities of 16 insecticides to second instars nymphs of A.spiniferus were measured by insects and leaves dipping method.The toxicity of bifenthrin andβ-cypermethrin were at last of all insecticides,and the 24h LC50 value of bifenthrin was only190.29 mg·L-1.The highest and the second toxicities were shown by the anthranilic diamide insecticide cyantraniliprole and chlorantraniliprole,the 24h LC50 values were 0.15 and 0.26mg·L-1 respectively,and reached 1268.60 times and 731.88 times of bifenthrin,respectively.Thiamide,chlorpyrifos,λ-cyhalothrin and spierothrin also showed high toxicities to nymphs of A.spiniferus,their LC500 values were all below 1 mg·L-1,and were 0.41,0.55,0.60,0.66mg·L-1 of each.The 24h LC50 values of imidacloprid,thiamethazine and tolfenpyrad were1.34,3.88 and 7.66 mg·L-1 respectively,and their toxities were more than 24 times of bifenthrin.And the LC50 of emamectin benzoate,indoxacarb,chlorfenapyr,flonicamid,dinotefuran were all above 20 mg·L-1,no more than 10 times of bifenthrin.2.In the field efficacy trials of the control of A.spiniferu,spirotetramat and cyantraniliprole in the dosage of 120 g（a.i.）·ha-1 had a good control,the correcting control efficiency to adults reached 70%,and to nymphs reached 90%.The control effects of pyrethroid insecticides,bifenthrin andλ-cyhalothrin,on adults and nymphs of A.spiniferu were 70%and 90%respectively.Neonicotinoid insecticides clothianidin’s control effect on A.spiniferu adults was low at lower dosages,even if at the dosage of 120 g（a.i.）·ha-1,the control effect was also less than 70%;lower dosages of clothianidin applied on nymphs showed high control effect,but the duration period were short;and when the spraying dosage was 120 g（a.i.）·ha-1,the control effect on nymphs was better,and ensure there were long duration period,the control effect after 7 days was reached 85.41%still.The control effect of chlorantraniliprole in the field is not good,at the third day,reached the highest control effect 64.14%;the control effect on nymphs was above 80%at the highest dosage of120 g（a.i.）·ha-1,while the control effect was lower when at the lower level of dosage.3.A method of Gas Chromatography-Mass Spectrometry（GC-MS/MS）was established to detect 6 insecticides in tea leaf samples.The QuEChERS method was modified to detect the residue of tea samples after field application.The degradation rate of thiamamine was the fastest,and the residual quantity of 120 g（a.i.）·ha-1 dose treated had been lower to 0.8398 mg·kg-1 at the seventh day,and the degradation rate of bifenthrin andλ-cyhalothrin,cyantraniliprole,chlorantraniliprole,spierothrin were also fast,but the maximum residue limit（MRL）of cyantraniliprole,chlorantraniliprole and spierothrin in EU were below 0.1mg·kg-1,and it may restrict tea export of China;while the MRL were lax of bifenthrin andλ-cyhalothrin in China,the residual quantity ofλ-cyhalothrin was under the MRL in the 120 g（a.i.）·ha-1 after applied in field 7 days,and bifenthrin was after 14 days,so their were all safe to use in the tea garden.4.Spirotetramat,cyantraniliprole,clothianidin,λ-cyhalothrin,bifenthrin,and chlorantraniliprole were the most efficient insecticides to A.spiniferus nymphs,the 48h acute toxicity of chlorantraniliprole,spirotetramat,cyantraniliprole,clothianidin on C.septempunctata larvae were lower;and the 24h LC50 value of bifenthrin andλ-cyhalothrin on C.septempunctata larvae reached 0.22 and 0.18 mg·L-1 respectively,which had a higher risk of predatory ladybirds. |
