Population Parameters Of Two Fruit Fly Species (Diptera: Tephritidae) Attacking Mango

ABSTRACT

Fruit flies (Diptera: Tephritidae) are among the most notorious pests damaging fruit crops

grown in Tanzania. Demographic and life history parameters of Ceratitis cosyra (Walker)

and Bactrocera invadens (Drew, Tsuruta and White) reared on artificial diet were

investigated at Sokoine University of Agriculture laboratory in 2010. Demographic and

life history parameters of C. cosyra and B. invadens were measured in an environmental

chamber at 250C and 300C with 75% RH to determine pre-adult survival and development

rates, adult survival and fecundity and life history parameters such as the intrinsic rate of

increase, the mean generation time and stable age distribution. The design of the

experiment was split plot arranged in a Complete Randomized Design (CRD) with three

replications. There were two sources of variations: Fruit fly species (being the mainfactor)

and temperatures (being the sub-factor). The effect of temperature and species on

eggs laying and survival were tested by two-way analysis of variance (ANOVA). The

Least significance difference (LSD) test was used to identify significant main effects. The

analyses were performed using GenStat package. The results show that B. invadens had

shorter egg incubation time than C. cosyra in all the temperatures tested. Larval and pupal

development rates of B. invadens were significantly faster than those of C. cosyra

independent of temperatures. Life expectancy of male B. invadens was significantly longer

than that of C. cosyra while life expectancy of female B. invadens was higher than that of

C. cosyra, however, the difference was not significant. The average net fecundity was

higher for B. invadens than was for C. cosyra. Both species attained their highest intrinsic

rate of increase and net reproductive rate at 30°C. Furthermore, B. invadens exhibited

higher intrinsic rate of increase and net reproductive rate than C. cosyra at all the

temperatures tested. These findings are useful for improving laboratory-rearing methods,

predicting the fly’s population dynamics, with a view to developing appropriate fly control

and management strategies.