The Effect Of Slow-Release Carriers And Background Odors On The Attraction Of Five Semiochemicals To Bactrocera Correcta

The guava fruit fly Bactrocera correcta(Bezzi)(Diptera: Tephritidae)is an economically important insect pest infesting fruits in tropical and subtropical regions.The primary studies of our team showed that d-limonene,β-caryophyllene,ethyl tetradecanoate,n-(3-methylbutyl)acetamide and octanal was attractive to female B.correcta individually in lab,but field trial had not been conducted to confirm their attractive effect.The attract of semichemicals identified in lab,were probably influenced by background odors and slow-release carriers in filed.In this research,the compounds in different carriers were extracted by the solvent extract and dynamic headspace absorption methods,and their quantity were measure by gas chromatography and ultraviolet spectrophotometer,then their outdoor release lifetime and release rates were compared.The orientation responses of female B.correcta to the compounds with and without background odors(odor form mature mango,guava,jujube,and peach,respectively)were measured in a wind tunnel.The catches of the female flies by d-limonene,ethyl tetradecanoate and n-(3-methylbutyl)acetamide with and without guava,mango and peach,respectively were evaluated in field cages.The study will provide basis for development of effective and safe attractant to B.correcta,and will provide important information for control this pest by semichemcials.The main results are showed as follows:(1)Except d-limonene and β-caryophyllene and n-(3-methylbutyl)acetamide in rubber septum(14.56 ± 0.38% and 44.60 ± 1.86% and 41.04 ± 3.23%,respectively),the entrapped rates of three compounds in different slow-release carriers were higher than 60%.The outdoor release lifetime of five compounds in liquid paraffin+centrifuge and silica sol-gel was not less than 28 d.The outdoor release lifetime of ethyl tetradecanoate,octanal,n-(3-methylbutyl)acetamide in rubber septum was more than 28 d,and that of d-limonene and β-caryophyllene in rubber septum was 19 d and 25 d,respectively.The outdoor release rates of d-limonene,n-(3-methylbutyl)acetamide and octanal in liquid paraffin+centrifuge tube,β-caryophyllene in silica sol-gel and ethyl tetradecanoate in rubber septum were stable and reasonable((249.35 ± 33.26)-(31.66 ± 0.71)μg/d and(78.26 ± 14.27)-(61.29 ±5.8)μg/d and(403.45 ± 10.28)-(5.87 ± 0.06)μg/d and(384.28 ± 71.56)-(9.33 ± 7.08)μg/d and(82.72 ± 4.28)-(14.81 ± 23.39)μg/d,respectively),and those of β-caryophyllene and ethyl tetradecanoate in liquid paraffin+centrifuge tube were also stable but too low((7.05±0.13)-(1.56±0.17)μg/d and(7.94±1.62)-(2.54±0.05)μg/d,respectively).Good volatile dispensers were of high entrapped rate,stable and reasonable release rates,long release lifetimes.Therefore,it suggested that liquid paraffin+centrifuge tube was the best slow-release dispenser for d-limonene,n-(3-methylbutyl)acetamide and octanal,rubber septum and silica sol-gel was best for ethyl tetradecanoate and β-caryophyllene respectively.(2)The wind-tunnel bioassays showed that the landing rate of mature virgin females onβ-caryophyllene and octanal with guava odor was significantly lower than that without guava odor(P<0.05),and there was no difference between the landing rate on other compounds with or without fruit odor(P>0.05).It suggested that guava odor decreased the attraction of β-caryophyllene and octanal to the mature virgin females,and other fruit odor did not affect the attraction of the compounds to them.The landing rate of mated females on five compounds with or without odors from 4 speices of fruits did not differ significantly(P>0.05),which suggested that the fruit odors could not influence the attraction of these compounds to them.The landing rate of mated females on the odor from mango,guava,jujube and peach was significantly higher than that of mature virgin females(P<0.05).The landing rate of mated females was higher than that of mature virgin females when they were exposed with ethyl tetradecanoate with mango odor,β-caryophyllene and octanal with guava odor,β-caryophyllene and n-(3-methylbutyl)acetamide with jujube odor,and d-limonene,β-caryophyllene and n-(3-methylbutyl)acetamide with peach odor,respectively(P<0.05).(3)The field cage experiment showed that the catches of female flies by d-limonene,n-(3-methylbutyl)acetamide and ethyl tetradecanoate with guava fruit was significantly higher that without fruit(P<0.05).The catches by d-limonene and n-(3-methylbutyl)acetamide with mango,as well as d-limonene and n-(3-methylbutyl)acetamide with peach did not differ from that by the individual compound(P>0.05).