Mortality of Carpophilus hemipterus eggs and larvae under the influence of thermal disinfestations

Abstract: The dry date cultivars grown in Israel pests may become infested in the orchard. Where pest management is insufficient, dates are brought to the warehouses with some Nitidulidae beetles and Phycitidae moths infestation. Therefore, to prevent further damage during storage within the warehouses and to remove the insects from the dates, insect control should be carried out by disinfesting the dates as they reach the packing stations. Thermal disinfestation technology has been successfully implemented by the transfer of hot air through a channel where dates are placed on trays. In earlier laboratory and commercial thermal disinfestation trials the effectiveness in disinfesting dates from larvae and adults was demonstrated. Exposure of dates to 50 °C for 3 h exposure was shown to be the most effective treatment for removing the insects from the dates and to control them. The present investigation was carried out during the development of the thermal disinfestation technology and addressed to examine the effectiveness of heat on eggs and larvae stage of Carpophilus hemipterus. In laboratory studies, the influence of 50 °C on the levels of mortality of C. hemipterus eggs was examined over a 3 h exposure period at r.h. of 20% to simulate commercial disinfestation treatments. Complete egg mortality was achieved after 3 h exposure. Since dates are disinfested at various moisture contents, the effect of r.h. on the effectiveness of the treatment was questioned. Therefore, on a separate laboratory experiment, survival of the larva stage of same species exposed to 50 °C at 15, 65 and 95% r.h. for 5, 30, 60, 90 and 120 min was examined. Complete mortality was achieved in all r.h. at a period above 60 minutes. There was no dependence of mortality on the r.h. level within the larva’s micro-environment.