Screen On Female Attractants Of Bactrocera Dorsalis And Its Role In The "Push-Pull" Technology

Bactrocera dorsalis(Hendel) is an important pest of fruits in southern China. Currently, methyl eugenol traps were used commonly to reduce B. dorsalis population in their integrated management. However, only B. dorsalis males were attracted by methyl eugenol traps, not the females. To solve this problem, female attractants were screened by a series of tests, and "push and pull" strategy was also used to improve the efficient of female B. dorsalis attractants. The main results are as follows:1. Nine chemicals were tested on attract efficient of B. dorsalis females. The experiment was conducted in an insect behavior observation chamber, and the nine tested chemicals are anisole, ?-pinene, D-limonene, caryophyllene, ?-pinene, ethyl benzoate,(E)-coniferyl alcohol, 2-allyl 4,5-dimethoxy and(Z)-3,4-methoxy cinnamic alcohol. Caryophyllene have the highest attraction which trapped 12.33 individuals/bottle females and the trapping rate reached 62%. Attraction effect of anisole and(Z)-3,4-methoxy cinnamic alcohol followed, which trapped 11.00 individuals/bottle and 8.33 individuals/bottle females, respectively; and their trapping rate reached 55% and 42%, respectively. Meanwhile, attraction of anisole on males is the same as its attraction on females, the trapped amount of males is 11.00 individuals/bottle, too; the trapping rate reached 55%. The results showed that anisole have strong attraction on females and males of B. dorsalis.2. Nine chemicals were tested on attract efficient of B. dorsalis females in different time period of a day. The results showed that five chemicals trapped more females at 17:01-21:00 period than at 9:00-13:00 period and 13:01-17:00 period. However, there is no significant different on the amount of trapped females of the five chemicals at 9:00-13:00 period and 13:01-17:00 period. The amount of trapped females by caryophyllene are 1.67 individuals/bottle, 3.33 individuals/bottle and 7.33 individuals/bottle at 9:00-13:00 period, 13:01-17:00 period and 17:01-21:00 period, respectively. The amount of trapped females by anisole at 17:00-21:00 period is higher than at 13:01-17:00 period. Behaviors of B. dorsalis and characteristics of these chemicals may contribute to the results.3. Seven common volatiles of B. dorsalis host plant including isobutyl acetate, ethyl acetate, decyl aldehyde, ?-terpinene, camphor, linalool and hexanol, were test on attraction of B. dorsalis. Meanwhile, EAG reaction of B. dorsalis on them were also test. The results showed that the attraction of all seven chemicals is significant higher than control. Decyl aldehyde, isobutyl acetate, ethyl acetate, and hexyl alcohol have best attraction on B. dorsalis females. Amount of trapped females by decyl aldehyde are 5.33 individuals/bottle and trapping rate is 27%. Amount of trapped females by ethyl acetate are 5.00 individuals/bottle and trapping rate is 25%. Meanwhile, all seven chemicals also have strong attraction to males. Amount of trapped males by ethyl acetate are 9.33 individuals/bottle and trapping rate is 47%. Amount of trapped males by hexyl alcohol are 8.67 individuals/bottle and trapping rate is 43%. Results of EAG test showed behavioral responses and electrophysiological activities of B. dorsalis are high to the seven chemicals. Corrected EAG values of B. dorsalis treated by hexyl alcohol, decyl aldehyde, ?- terpinene, and isobutyl acetate are 2.566, 2.365, 2.108, and 1.858, respectively. However, linalool and camphor did not show strong attraction to females. Our results also showed that the results of behavior test may not correspond to the results of EAG test completely.4. The luring effects of different attractants mixture on B. dorsalis. Each two substances of the nine chemicals including anisole, ?-pinene, D-limonene, caryophyllene, ?-pinene, ethyl benzoate and other attractant substances were mixed, and then, their attraction effects were test. The results showed mixture of anisole and caryophyllene in accordance with 6:4 ratios have strongest attraction to females with an average of 14 individuals/bottle and 70% trapping rate. However, after adding several other attractants in the mixture, the attraction was not increased.5. Discussion on the application of B. dorsalis attractants in "push and pull" strategy. The results showed that the existence of repellents have significant effects on the amount of trapped females by attractants. When garlic oil was taken as repellent, the amount of trapped females by attractants were highest, reached 11.00 individuals/bottle. When citronella oil was taken as repellent, amount of trapped females 9.33 ± 0.67 b individuals/bottle by attractant, while amount of trapped females by control was only 5.33 individuals/bottle. The results of orthogonal experiment showed concentration of attractants, ratio of attractants and repellents have significant impact on amount of trapped females in three factors including concentration of attractants, ratio of attractants and repellents, and ratio of two different attractants in the mixture. 50% is most suitable concentration of attractants. The suitable ratio of attractants and repellents is 4:1. The trapping rate of females by the optimal combination(30% attractant and ratio of attractants and repellents is 4:1) can reach 80%. We also investigated the suitable distance between attractants and repellents in the field. Our results showed the attractant trapped more females than other distance when the distance is four meter between attractants and repellents.