Studies On Spatiotemporal Distribution And Control Of Bactrocera Minax

Bactrocera (Tetradacus) minax is a devastating pest which harms the citrus mainly by the larvae which grow inside the citrus fruit. So it is difficult to control this pest through spraying of pesticide. Trapping and killing in adult life stage is one of the important parts of the IPM of B.minax. Since then, understanding of spatial and temporal distribution of B.minax adults is the important foundation of controlling this pest. In this article, we studied migration of B.minax in citrus orchard and woods after eclosion using geographic information technology. Besides, we also investigated spawning distribution of B.minax adults. Above all this, we tested new lure methods and microbial source baits.In this study, we have got the clear understanding of migration of B.minax after emergence. Spatial and temporal distribution of B.minax in the citrus orchards showed close correlation with changes over time. Emergence peak occurred on June11th with433adults being trapped that day. During eclosion peak of B.minax, from June2nd to June20th, more than60%of flies mainly appeared in the junction area of citrus orchards5m sampling zone and the hybrid woods5m sampling zone. Especially on June2nd, the number of flies caught on this region was significantly higher which accounts for87.5%of the total. In June11th, the numbers of flies trapped in5m sampling zone of citrus orchards were74.7±21.9insects per trap. While the numbers of flies trapped in5m sampling zone of hybrid woods were24±5.6insects per trap. The number of flies caught in the trap decreased with time after eclosion period (June26th). Furthermore, the flies distributed uniformly in the orchards with the exception of hybrid woods100m sampling zone in which no flies were caught.GIS technology was used to analysis of spatial and temporal distribution of B.minax in citrus orchards and its surrounding environment. The results showed that from eclosion began period (June2nd) to the emergence peak period (June11th), B.minax population density expand at the junction region with aggregation phenomenon. With time relapse, the activity of B.minax populations moved inside-wards the citrus orchards, and the population density is drastically reduced. According to the monitoring data of different periods and different monitor points, we use GIS technology to draw the distribution picture of B.minax in eclosion period and post eclosion (egg laying) period. The results showed that during the eclosion peak period, the density of adult flies in the hybrid wood is the highest with120-160insects per monitoring point while the number is smaller in other point as<40or between40and80insects per point. After eclosion peak, the number in each monitoring point dropped drastically while the highest number in>40insects per monitoring point. Besides, most of the monitoring points which have highest numbers were inside the citrus orchards.Investigation of oviposition marks in the fruit surface revealed that the marks were unevenly distributed on the surface of citrus. The numbers of marks were significantly different in different parts of citrus fruit. Numbers were largest in the waist part of fruit with6.4±0.4/fruit. The number is significantly high than in the stem end (0.9±0.1fruit) and in fruit umbilical (1.6±0.2/fruit),4times and7times each. The numbers of oviposition marks in the shady side of the fruit were7times higher than the numbers in the sunny side. These results showed that compared with the stem end and fruit navel, citrus fruit flies prefer to lay eggs in fruit waist. Besides, citrus fruit flies prefer the shady part of the fruit surface. However, the flies showed no preference towards the spatial location of the citrus fruit and no difference could be observed among fruits located in East, West, North and South of the tree. What is more, no significant differences could be observed in oviposition marks on the crown of the upper and the lower part of the tree. At the same time, we analyzed the average number of the oviposition marks in different sampling zone in the citrus orchard. Results showed that there is no siginificant difference of the oviposition marks in different sampling zone.According to the results of the occurrence regularity of B.minax in the orchard, we adopted a series of experiments to compare the controlling effect of different controlling methods. The results showed that B.minax adults trapping work should be done during the period of emergence peak,7.6±1.8insects were trapped per trap per day, while1.8±0.3insects were trapped per trap per day in spawning period. Considering the distribution of traps in citrus orchard, traps should be setting in the junction area of citrus orchards and hybrid woods. The trapping number in junction area was29.0±4.9per trap, which was significantly higher than17.2±2.2per trap in orchard. But in spawning period, prevention in orchard is better than in junction area. The controlling effects about spawning marks and wormed fruits showed that there is no significant difference between trapping during emergence peak period in the junction area and trapping during whole adults hazard period in orchard. But considering about the economic factors, trapping during emergence peak period in the junction area can save human resources and financial supporting. It’s more operable than trapping during whole adult hazard period in orchard which always lasts two months.Through field experiments, we compard the luring effect of six yeast, one Rhizopus and one Aspergillus fermentation broth to B.minax. Finally, two kinds of yeast exhibited a better effect during the experiment. Papain was added to yeast fermentation broth for hydrolysis process. Through this process, we got a microbial source bait that mainly base on JM2hydrolysis fermentation broth. The bait’s lure effect was3.52times compared to the sweet and sour liquid control group and significantly better than other formulations. Different dilutions and the persistence of the optimized formulation were compared. The results showed:In consideration of economy and attracting effect, formula showed better effect when diluted to2times. Bait keeps effect for no more than4days. Finally, we also tested the luring effect of the microbial source bait to Bactrocera dorsails Hendel.