The Attract And Kill Technique For The Control Of Bactrocera Minax (Enderlein)

The Chinese citrus fruit fly, Bactrocera minax (Enderlein) is a serious tephritidae pest that infests Citrus genus. It is mainly distributed in Hubei, Hunan, Sichuan, Guizhou, and Chongqing of China. The occurrence of B. minax is getting more and more serious in recent years in China due to climate change, adjustment of the plantation structure and frequent trade contacts. However, the management against B. minax was still restricted in traditional methods, such as agricultural sanatition, chemical control with a mixture of brown sugar and vinegar. Thus, the development of effective techniques for suppressing populations of B. minax is necessary. In this study, we focus on attract and kill techniques against B. minax. First, the mouthpart structure of B. minax adults was observed by scanning electron microscope. Second, protein baits were developed and implemented to attract and kill the Chinese citrus fruit fly both under laboratory conditions and in the field. In addition, a kind of self-made fruit-mimicking model especially for B. minax was established and tested in the field. The main results are as follows:1. The mouthparts of B. minax were observed with scanning electron microscope. The results suggest that there are many prestomal spines between labella, which can interlock across the oral opening; the labellum has a series of fine tube-like structures, called pseudotracheae, on its inner surface. These pseudotracheae contain fine micropores formed by a series of opposing rings. Mouthparts of B. minax are similar in general structure to other Bactrocera species; thereby they have the same labellar filtering mechanism. These specific structures and feeding mechanism determine that adult flies can ingest food particles and liquids which were ingested only through fine micropores on the pseudotracheae.2. Based on the above results, the protein bait is made of an enzymatically hydrolyzed protein that is produced to small molecular from the industrial processing of beer yeast. Small molecular protein hydrolysate is produced from brewst yeast with protein enzyme. Protein bait is prepared using the hydrolyzed protein; other additives include ammonia acetate, brown sugar and orange juice. The protein bait is tested in laboratory bioassay and field evaluation.Laboratory bioassay results showed that:(1) The protein bait showed the best average attractive rate of 63.33% to 7-day-old B. minax adults when the test was studied with 3 to 10-day-old adults; the best attractive rates for 3 to 10-day-old females and males were 7-day-old of 66.67% and 8-day-old of 61.67%, respectively. (2) The relative attractive rate of protein bait was 4.76 and 7.5 times respectively when comparing with torula yeast and sugar-vinegar-wine mixture for B. minax.Field test results suggested that:(1) All treatments differed significantly from each other both in females and males catch when comparison of attractiveness tests were conducted among aqueous solutions of protein bait, sugar-vinegar-wine mixture, torula yeast and Jufeng attractant in traps. Traps baited with protein bait caught significantly more females and males than other lures. (2) In spot spray test, protein bait killed significantly more females and males within 40 mins than treatments of sugar-vinegar-wine mixture, GF-120, Jufeng attractant and water (blank control). Total number within persistent duration for each treatment differed significantly in function of treatments. Protein bait caught significantly more females and males than Jufeng attractant and control, whereas marginally more than GF-120. All results indicated that protein bait showed a better attractiveness for B. minax.3. Three sizes of plastic spheres (8,14, and 18 cm diameter) combined 3 colors (orange, green and green-yellow) were evaluated as unbaited sticky-coated traps for attracting B. minax in field. There were significant differences among these 9 treatments for attractiveness of adults.14 cm green-yellow trapped more females and males than other spheres. Moreover, this fruit-mimicking sphere showed great and stable attractiveness for both females and males in field tests. It can be used as a trapping device for B. minax in the future.The protein bait and self-made fruit-mimicking trap especially for B. minax were all proved very well in our test. These attract and kill techniques provide powerful tools for sustainable management of B. minax.