Screening Of Attractant For Harmonia Axyridis And Control Of Four Functional Plants On Main Pests In Peanut Field

Peanut’s above-ground pests thrips and aphids have increased significantly in recent years,not only directly harming crops but also transmitting a variety of viral diseases,which often cause huge economic losses.Traditional chemical control causes a series of problems such as "3R" problem and killing natural enemies,which affect the environment and agricultural product safety.So it is urgent to seek green and harmonious control approaches.Plant volatiles and insect pheromones can be used as attractants to attract natural enemies of the habitat around the crops.Function plants provide food,habitat and shelter to natural enemies.Harmonia axyridis,an important predator of aphids and thrips,was selected as the research object;the compound formula with higher attractant activity was screened by behavior experiment and field trapping test.Planting four functional plants next to peanuts to form three treatments of functional plants,Veronica persica(May 30-June 15)+Helianthus tuberosus(June 15-September 7)+ peanut,Cichorium intybus + peanut and Zinnia elegans + peanut.The microlandscapes constituted of peanut and functional plants were considered as research systems.The occurrence dynamics of four major natural enemies(Syrphidae,Coccinellidae,Anthocoridae and Aphidiidae),thrips and aphids in these microlandscapes were studied.The main results are as follows:1.Screening for formulas in laboratory and evaluation of attractant effect in the field for H.axyridisY-tube olfactometers were used to conduct olfactory tests on females and males of H.axyridis,respectively.The optimum attractant concentrations of 8 compounds were obtained.The dosage of each monomer compound in the compound formula was determined,and the formulas with strong activity to the test insects were further screened with different combinations.The results showed that four formulas,(E)-β-Farnesene + Indole,(E)-β-Farnesene + Methyl anthranilate,(-)-β-Caryophyllene +(E)-β-Farnesene + Methyl anthranilate,(-)-β-Caryophyllene +(E)-β-Farnesene + Indole showed significant activity on male and female adults,with the choice reaction rates above 90%.2.Effects of functional plants on the occurrence and dynamics of natural enemies in peanut fieldsThe results showed that the four main families of natural enemies in peanut fields were Syrphidae,Coccinellidae,Anthocoridae and Aphidiidae.The total amount and occurrence dynamics of four natural enemies in the whole area of functional plants +peanut were investigated at 10 time points.The results showed that the treatment of V.persica +H.tuberosus had a significant attraction effect on Syrphids and the total amount of occurrence was 1.85 times higher than that of peanut monocrop plots.From July 21 to August 2,H.tuberosus attracted significantly more Coccinellids compared with Z.elegans treatment plot,C.intybus treatment plot and peanut monocrop plots,and the numbers of lured insects were 1.65,0.31,0.97 and 0.13 heads,respectively.From July 12 to August 22,the attraction effect of Z.elegans treatment on the natural enemies of Syphoridae was significantly higher than that of C.intybus treatment plot,V.persica+ H.tuberosus treatment plot and peanut monocrop plot,and the numbers of lured insects were 0.55,0.16,0.09 and 0.09 heads,respectively.In addition,the total number of Coccinellids,Anthocorids and Aphidiids in Z.elegans treatment plot were 2.44,3.02 and 2.34 times higher than those in peanut monoctrop plot,respectively.The total number of Coccinellids and Aphidiids in C.intybus treatment plot were 3.35 and 2.73 times higher than that of peanut monocrop plot,respectively.3.Effects of three functional plant treatments on population dynamics of thrips and aphids in peanut fieldsField investigation showed that the main species of thrips in peanut field were Frankliniella intonsa,Haplothrips aculeatus and Anaphothrips obscurus and the main aphids were Aphis craccivora.The sum of the 10 investigation results showed that the total number of F.intonsa on peanut in each of the three groups of functional plant treatment area was significantly lower than that in the peanut monocrop plots.The decrease rate of F.intonsa on peanut after planting V.persica or H.tuberosus alone was7.32% and 27.97%,respectively.The decrease rates of F.intonsa on peanuts in C.intybus treatment plot and Z.elegans treatments plot were 14.06% and 11.67%,respectively.The number of H.aculeatus in peanut in each of the three groups of functional plant treatment plot was significantly lower than that in the peanut monocrop plots and the decrease rate of H.aculeatus in peanut area after planting V.persica or H.tuberosus alone was 82.86% and 19.32%,respectively.The decrease rates of H.aculeatus on peanuts in C.intybus treatment plot and Z.elegans treatment plots were64.77% and 43.18%,respectively.Except for C.intybus treatment plot,the total numbers of A.obscurus on peanuts in V.persica + H.tuberosus treatment plot and Z.elegans treatment plot were significantly lower than that in peanut monocrop plots,and the decrease rate of A.obscurus on peanuts after plating V.persica or H.tuberosus alone was 24.33% and 35.33%,respectively;In the Z.elegans treated plot,the decrease rate of A.obscurus on peanuts was 23.37%.Field investigation showed that the peak of A.craccivora occurred before May 30.There was no significant difference between the number of functional treatment areas and the peanut monoculture plot,which may be related to the low amount of occurrence.To sum up,The laboratory and field tests of the combination of attractants for H.axyridis showed that: two formulas,(E)-β-Farnesene + Methyl anthranilate,(-)-β-Caryophyllene +(E)-β-Farnesene + Methyl anthranilate showed significant attractant effect and had the potential to develop attractants.Based on field investigation of the impact of four functional plants on the four families of natural enemies and thrips,V.persica has attractant effect on Syrphids;C.intybus has attraction effect on both Coccinellids and Aphidiida;H.tuberosus has attraction effect on Coccinellids;Z.elegans has attraction effect on all the four families of natural enemies.All the three treatments of functional plants had control effects on T.tabaci and H.aculeatus on peanut.The treatments of V.persica + H.tuberosus and Z.elegans had control effects on A.obscurus on peanut.The results provided a theoretical basis for establishing the control system of functional plants combined with attractants.