Investigation on sugarcane borer egg parasitism by parasitoid wasp, Telenomus busseolae in plant and ratoon crops

The egg parasitoid wasp, Telenomus busseolae Gahan (Hym.: Platygastridae) is the most important natural enemy of sugarcane stem borers in sugarcane growing area of Khuzestan province. In order to know the parasitism rate of T. busseolae in plant crops compared with first ratoon crops an investigation was carried out in Amir-Kabir Agro-industry in southern Khuzestan. In this study six plant and six ratoon cane fields of commercial sugarcane cultivar, CP69-1062 was selected and sampling of sugarcane borers (Sesamia spp.) egg batches was made monthly from April to November. The results indicated that field age and sampling time has a significant effect on egg batch densities of sugarcane borers and parasitism of eggs by T. busseolae. The lowest egg batch density was observed in April and the highest was recorded in September both in plant crops and first ratoon crops. In plant crops the lowest egg parasitism rate (43.5 %) was observed in July, whereas the highest rate (84.4 %) was observed in April.  In the first ratoon crops the lowest rate of parasitism (38.8 %) was observed in June and then increased to 87.3 % in November. The percentage of adult emergence of T. busseolae was not significantly influenced by crop age and sampling time.There was no significant difference of progeny sex ratio in the two investigated crop ages, but sampling time significantly influenced on progeny sex ratio. The results of this study provide useful information on the population fluctuations of T. busseolae in plant and ratoon crops of sugarcane.