The cowpea weevil, Callosobruchus maculatus F. (Coleoptera: Bruchidae), is an important pest of stored cowpea, Vigna ungiculata (L.) Walpers (Fabales: Fabaceae), with ample distribution in tropical and subtropical regions. Many plant essential oils have a broad-spectrum activity against pest insects, and these oils traditionally have been used in the protection of stored products. In this study, the lethal and sublethal effects of essential oils from Eucalyptus camaldulensis Dehnh. (Myrtales: Myrtaceae) and Heracleum persicum Desf. (Apiales: Apiaceae) were evaluated on the adults of C. maculatus at 26 ± 1° C, 70 ± 5% RH, and a photoperiod of 16:8 L:D. The LC50 values of E. camaldulensis and H. persicum were 56.7 and 219.4 µL/L air after 12 hr and 26.1 and 136.4 µL/L air after 24 hr of exposure, respectively. The LT50 values of E. camaldulensis and H.persicum were 6.3 and 10.9 hr, respectively. The results showed that low lethal concentration (LC20) of essential oils negatively affected the longevity, fecundity, and fertility of female adults. The sex ratio of C. maculatus offspring was not significantly affected by essential oils. Therefore, these essential oils can be suggested for controlling C. maculatus in storage systems. The introduction of essential oils into storage systems could potentially decrease seed losses.

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Abstract:Habrobracon hebetor Say is one of the most important natural enemies of the Helicoverpa armigera Hübner (Lep.: Noctuidae). In this study, the sublethal effects of LC 30 concentration of azadirachtin, cypermethrin, methoxyfenozide and pyridalil on the functional response of H. hebetor to different densities of 5th instars larvae of Ephestia kuehniella Zeller were evaluated. Young females were exposed to LC 30 of the insecticides for an appropriate time of exposure. Then, six randomly selected alive females were transferred individually to plastic Petri dishes (10 cm in diameter) and supplied with the following densities: 2, 4, 8, 16, 32 and 64 of 5th instars of E. kuehniella for 24 h. Eight replicates were considered for each insecticide treatment and the control. The results revealed a type II functional response in the control, and all of the insecticide treatments. This study showed that the control and the cypermethrin treatment had the shortest (0.4143 h) and longest (0.624 h) handling time, respectively. The highest (0.0035 per hour) and lowest (0.0029 per hour) attack rate was observed in pyridalil and cypermethrin treatments, respectively. Based on values of handling time, cypermethrin had the highest adverse effect on host-finding in H. hebetor.

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Habrobracon hebetor Say is one of the most important ectoparasitoids of the larval stage of many invasive agricultural pests such as noctuid and pyralid moths. Lethal and sublethal effects of carbaryl and abamectin were assessed on the ectoparasitoid H. hebetor in laboratory conditions. Dose-response bioassays were carried out on immature and adult stages by using dipping and contact residue methods, respectively. LC 50 (lethal concentration for 50%) values of carbaryl and abamectin were 31.19 and 4.16 mg a.i. l -1 on larval stage and 12.6 and 4.42 mg a.i. l -1 on adults, respectively. In order to assess the sublethal effects, adult wasps were exposed to an LC 30 of each insecticide and then the demographic parameters of live wasps were studied. The results showed that the intrinsic rate of increase (r m ), finite rate of increase (k), net reproductive rate (R 0 ) and gross reproductive rate (GRR) were significantly affected by the insecticides. The highest and the lowest r m values were 0.23 and 0.17 in control and carbaryl-treated insects, respectively. The sex ratio of H. hebetor offspring was not significantly affected by either insecticide. The results showed that carbaryl had more adverse effects on population parameters of the parasitoid compared to abamectin. Field studies are needed to determine the total effects of the pesticides on H. hebetor.