Demographic Analysis of Sex Ratio on Population Growth of Bactrocera Dorsalis (Diptera: Tephritidae) With Discussion of Control Efficacy Using Male Annihilation

Abstract

The life table data for the oriental fruit fly, Bactrocera dorsalis (Hendel), at different adult sex ratios (1 female: 1 female, 1 female: 50 male, 50 female: 1 female free-choice mating, and 50 female: 1 male no-choice mating) were collected to determine the effects of sex-ratio manipulation on current pest control procedures. At 1 female: 1 male, females mated, on average, 2.3 times during their lifetime with a mean fecundity (F) of 1,122 eggs. The net reproductive rate (R-0), intrinsic rate of increase (r), finite rate (lambda), and mean generation time (T) were 561.0 offspring, 0.1693 d(-1), 1.1844 d(-1), and 37.4 d, respectively. At 50 female: 1 male free-choice mating, males mated 46.7 times during their lifetime, while at 50 female: 1 male no-choice mating, males mated on average 50 times during their lifetime, and all females mating only once in both treatments. The values for F, r, and lambda were significantly lower for both 50 female: 1 male treatments than those in the 1 female: 1 male group; the R-0 values, however, were either equal to or even higher than those in the 1?: 1? treatment. In the male-biased sex ratio (1 female: 50 male), fecundity was the highest (1,610 eggs) and female average life span the longest (166 d), while the R-0 was the lowest (31.6 offspring) among all treatments. Population projections showed that even at a sex ratio of 50 female: 1 male, B. dorsalis could still produce a large number of offspring. These findings demonstrate that management strategies for controlling B. dorsalis could be properly evaluated by using demographic methods. Because female annihilation appears to be a more effective control strategy, it should be considered as a viable alternative.