تاثیر حشره‌کش آزادیراختین روی شاخص‌های تغذیه‌ای Plodia interpunctella (Lepidoptera: Pyralidae) روی میوه‌های مختلف خرما

One of the important storage pests of dates is the Indianmeal moth, Plodia interpunctella Hubner (Lep.: Pyralidae). Indianmeal moth is a polyphagous insect that causes serious damage to various food products in warehouses. In this experiment, nutritional indicators of fourth instar larvae of P. interpunctella were investigated on date varieties treated with 4 ppm of azadirachtin insecticide and control (distilled water). The experiment was performed in 10 replicates, and one fourth-instar larva was released in each dish. The weight of larvae before and after of feeding, the feces weight, the weight of given and remained food was counted daily until the emergence of the pre-pupae based on dry weight. In the control, the highest digestibility index (AD) was calculated in Zahedi variety, 78.20% and the lowest was calculated in Estemaran, 53.70%. In Dayri, Halavi and Zahedi varieties, azadirachtin significantly reduced AD and its values were 49.21, 66.85 and 74.29%, respectively. The high digestibility and growth rate of an insect indicates the appropriateness of feeding the host plant by that insect. The high digestibility index in Zahedi variety can be a proof of desirability of the host plant for its feeding by the pest. The highest conversion efficiency of food (ECI) in the control was calculated as 1.7 and 1.68% respectively in Estemaran and Zahedi varieties and the lowest was in Dayri and Halavi, 1.29 and 1.31%, respectively. In all tested varieties, azadirachtin significantly reduced ECI. In the control, the highest conversion efficiency of digested food (ECD) was found on Estemaran variety, 3.25% and the lowest on Halavi variety, 1.76%. In Fersi and Halavi varieties, azadirachtin decreased ECD, which were 1.83 and 1.42%, respectively. In the control, the highest relative growth rate (RGR) was observed in Zahedi, Halavi and Dayri varieties. In all date varieties, except for Estemaran, the relative growth rate (RGR) in larvae fed with azadirachtin was significantly lower than the control. In the control, the highest relative consumption rate (RCR) was reported in the larvae fed on Zahedi, Estemaran and Fersi varieties. In Dayri, Halavi and Zahedi varieties, the RCR rate of P. interpunctella larvae treated with azadirachtin showed a significant decrease. The higher ECI of the larvae fed with Estamaran, Zahedi and Fersi can indicate the high rate of conversion of food of these varieties to body biomass compared to Dayri and Halavi varieties. In this study, the highest RCR and RGR were observed in the larvae fed with Zahedi variety, which indicates the high quality of this variety for feeding and growth of P. interpunctella. The low nutritional indices of the larvae treated with azadirachtin can be attributed to the anti-nutritional property of azadirachtin, which reduces the digestibility of food.