Biological Control Technologies Of Grapholita Molesta (Lepidoptera: Tortricidae) And Their Effects On Fruit Quality In Pear Orchard With Reduction Of Pesticides And Unbagged

Pear industry in China lies at the top of the world in planting area,output and exports.Grapholita molesta(Busck)(Lepidoptera: Tortricidae)is one of the worldwide boring fruit pests.Larval damage to pear fruits to seriously restricted the economic benefits and industry development.The use of pesticides and fruit baggings have been the main control methods against G.molesta in pear orchard.However,they caused a series of problems,such as declining pear quality,food safety,insecticide resistance,killing natural enemies and pollinators,high labour cost and so on.Recently,insect sex pheromones is widely concerned,because of non-toxicity,high efficiency and specificity,as well as goodness for our environment.In 2016 and 2017,we carried out comparative experiments of control effects among the 6 different combinations,including mass trapping,either tube or bottle of mating disruption,natural enemies,tube of mating disruption + natural enemies and bottle of mating disruption + natural enemies in the different pear orchard with reduction of pesticides and unbagged including Su pear,Yuluxiang pear and Xuehua pear of Qi county,Jinzhong city,Shanxi province.Meanwhile,fruit quality was investigated in these pear orchards where fruit grower used the less pesticides and non-bagging techniques.Through the comparison of control effects and fruit qualities with conventional managements which included more chemical pesticides and fruit bagging.We aimed to determine the green,high-efficient,high-quality,sustainable development and ecological control technology.Our main results were as follows:1)Among different treatments,bottle of mating disruption and bottle of mating disruption + natural enemies had the good control effects on the Xuehua pear.The rate of G.molesta damage to fruits decreased by 78.2 % and 75.8 %,respectively.Bottle of mating disruption + natural enemies had the good control effect on the Su pear.The rate of G.molesta damage to fruits decreased by 64.8%.Natural enemies had the good control effect on Yuluxiang pear,and the rate of G.molesta damage to fruits decreased by 66.3%.There was no significant difference in the rate of G.molesta damage to fruits based on between bological control above and conventional management.2)The appearance quality of non-bagging pear was compared with bagging pear.The clearness index decreased by 35.91%,23.31% and 30.76% on Su pear,Yuluxiang pear and Xuehua pear,respectively.Fruit rust index increased by 4.72% and 7.78% on Su pear and Xuehua pear,respectively,while fruit rust index decreased by 14.31% on Yuluxiang pear.There was no significant difference in fruit shape index and fruit weight between bagging pears and non-bagging pears.Meanwhile,the edible quality of non-bagging pear was compared with bagging pear too.Total sugar content and total acid content increased on the three pear varieties.Total sugar content of Su pear,Yuluxiang pear and Xuehua pear increased by 11.89%,17.84% and 2.35%,respectively,and total acid content increased by 21.11%,29.17% and 17.81%,respectively.Moisture content of Su pear and Yuluxiang pear decreased by 1.18% and 2.37%,respectively.There was no significantly different in hardness,protein content and chewiness.3)Pesticides reduction is defined as the types and times of pesticides application reduction The imidacloprid residues of Su pear and Yuluxiang pear decreased by 100% and 65.52%,respectively.The total arsenic residues of Yuluxiang pear and Xuehua pear reduced by 32.14% and 65.71%,respectively.The cypermethrin was not used on Yuluxiang pear,compared with contrast which had the residual quantity,0.013 mg /kg.The appearance quality of pear with pesticides reduction was compared with more pesticides application.Clearness index of Su pear,Yuluxiang pear and Xuehua pear decreased by 24.61%,6.06% and 10.77%,respectively.Fruit rust index of Su pear and Yuluxiang pear increased by 8.69% and 4.73% respectively,while fruit rust index of Xuehua pear decreased by 4.03%.There was no significant difference in fruit shape index and fruit weight between the two pesticides application.The intrinsic quality of pear was compared too,soluble solids content of three pear varieties were both increased.In particular,soluble solids content of Yuluxiang pear and Xuehua pear significantly increased by 6.49% and 7.82%,respectively.Total acid content of Su pear and Yuluxiang pear significantly increased by 32.34% and 50.19%,respectively.There was no significant difference in hardness,chewiness,total sugar content,protein content,moisture content and vitamin C.Overall,biological control measures,such as bottle of mating disruption control,bottle of mating disruption + natural enemies and natural enemy not only decreased G.molesta populations,but also reduced the pesticides residue and enhanced flavor of pears in pear orchard with non-bagging cultivation and pesticides reduction.The biological control measures have potentials of application and promotion,which can be helpful for the industry supply reform,energy efficient cultivation,safety,high-efficiency,high-quality,green and even the organic ecological modern agriculture development of pear.