Effects of different food treatments on biological parameters of Bracon hebetor

Adult insects of many parasitoids use carbohydrates to supply their energy. A high-carbohydrate diet increases the efficiency and other biological properties of parasitoids. Bracon hebetor Say (Hym: Braconidae) is one of the most important biological control factors on farms, orchards, and forests of the country, widely perceived to be found in nature, and can be effective in controlling larvae of leprose winged pests at an acceptable economic cost.

Materials and Methods:

 In this study, the effect of four sugar treatments [10% concentration of fructose, glucose, honey, and a mixture of fructose, glucose, and honey (1:1:1)] and distilled water (as a control for sugar treatments) was examined on the biological properties of B. hebetor male and female adults. B. hebetor was reared on fifth instars of Ephestia kuehniella Zeller (Lep: Pyralidae) in a growth chamber at 26±2 ºC‚ 60±5 %RH‚ and photoperiod of 16:8 (L: D) h. Daily observations and records were made for the development period and survival rate. The data were analyzed based on two-sex life table analysis using TWO SEX-MS Chart.

The present study showed a significant improvement in the biological reproductive and stable population parameters in sugar treatment groups compared with the distilled water treatment. The highest value of adult longevity and life expectancy (ex) of the B. hebetor occurred in fructose treatment. Moreover, the highest net reproduction rate(R0), finite rate of increase(λ), and lowest doubling time (DT) were observed in the mixed sugar treatment. On the other hand, the highest gross reproduction rate (GRR) and mean generation time (T) were found in glucose and fructose treatments. The results of study revealed that intrinsic rate of increase (rm) values for distilled water, fructose, glucose, honey, and mixed sugar were 0.257 ± 0.001, 0.272 ± .0011, 0.267 ± 0.033, 0.264 ± 0.007, and 0.291 ± 0.004 (day-1), respectively.

According to the results of the present study, B. hebetor was positively affected by the sugar treatments, and the suitability of sugar diets was ordered as mixed sugar > fructose > glucose and honey. In conclusion, sugar feeding is recommended for the mass rearing program of B. hebetor because suing them could increase the ability of this parasitoid in pest control. The highest rm value for the mixture of the three sugars indicated the importance of sugar-feeding quality in the mass-rearing program of natural enemies.