Population dynamics of Bactrocera dorsalis and the damage caused by this pest in citrus orchards

Author of the article:WANG Ming-Zhao** YANG Ting-Mi*** LI Xian-Liang LOU Bing-Hai HUANG Hui-Ying ZHAO Xiao-Long ZHANG

Author's Workplace：(Guangxi Academy of Specialty Crops, Guangxi Key Laboratory of Citrus Biology, Guilin 541004, China)

Key Words：Bactrocera dorsalis; citrus; increase and decline; damage

Abstract： [Objectives]  To investigate the population dynamics of Bactrocera dorsalis in citrus orchards in the eastern suburbs of Guilin, and improve techniques to control the degree of damage inflicted on different citrus varieties by this pest. [Methods]  Numbers of B. dorsalis in orchards were monitored using sex pheromone traps from 2012 to 2013. Seasonal fluctuations in abundance were analyzed and the number of damaged fruit on different citrus varieties, including early-maturing, middle-maturing and late-maturing, varieties was compared before, and after, ripening. [Results]  B. dorsalis began to appear in May, reached peak abundance between late September and early October, and declined or disappeared from orchards in mid to late December. Damage to early and middle maturing varieties was 26.73%-73.19% whereas damage to late-maturing varieties was below 16.08%. Damage to loose-skin mandarin varieties was above 15.23% whereas damage to orange and hybrid varieties was below 10.81%. Fruit of early-maturing varieties was damaged from July or August until they were ripe, and the degree of damage gradually increased during this period. Damage to middle and late-maturing varieties began to appear from mid to late October, had 1 or 2 peaks between early November and early December, then decreased from mid to late December. The beginning, peak, and low damage periods in the same variety were not identical in different years. [Conclusion]  B. dorsalis becomes active in spring when conditions are suitable, reaches peak activity in autumn, and decreases or ceases activity under adverse conditions such as falling temperatures. Damage to early and middle-maturing varieties was higher than to late-maturing varieties, and damage to loose-skin mandarin varieties was higher than to orange varieties. During the process of fruit growth and development, the proportion of damaged fruit on early-maturing varieties increased as fruit matured; peak damage to middle and late-maturing varieties first appeared as early maturing fruit ripened, or during the middle period of fruit development. The increase and decline in the number of damaged fruit that ripened at the same time of year was basically the same within the same year, but the increase and decline in the number of damaged fruits in the same citrus variety was not the same in different years.