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Third instar larvae of the cotton bollworm (Helicoverpa armigera) were reared with artificial diet containing a Bacillus thuringiensis - abamectin (BtA) biopesticide mixture that resulted in 20% mortality (LD20). The adult male survivors from larvae treated with BtA exhibited a higher percentage of “orientation” than control males but lower percentages of “approaching” and “landing” in wind tunnel bioassays. Adult female survivors from larvae treated with BtA produced higher sex pheromone titers and displayed a lower calling percentage than control females. The ratio of Z-11-hexadecenal (Z11–16:Ald) and Z-9-hexadecenal (Z9–16:Ald) in BtA-treated females changed and coefficients of variation (CV) of Z11–16:Ald and Z9–16:Ald were expanded compared to control females. The peak circadian calling time of BtA-treated females occurred later than that of control females. In mating choice experiment, both control males and BtA-treated males preferred to mate with control females and a portion of the Bt-A treated males did not mate whereas all control males did. Our Data support that treatment of larvae with BtA had an effect on the sex pheromone communication system in surviving H.armigera moths that may contribute to assortative mating.

The effects of the mixed biocide Bacillus thuringiensis Berliner with abamectin (BtA) on the development of the parasitoid Microplitis mediator (Haliday) (Hymenoptera: Braconidae) and its cotton bollworm host, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), were evaluated in the laboratory. Weight gain in larvae of H. armigera was initially delayed, but larval developmental period increased and pupal weight increased when they were fed on a diet containing BtA. Due to increased longevity of the host larvae, the susceptible period to parasitization of H. armigera by M. mediator increased when the host larvae were reared on diets containing BtA at concentrations of 0.5, 1, 2, and 4 μg g−1. The longevity of female and male parasitoids significantly decreased when newly emerged wasps were fed a honey solution containing 200 μg ml−1 BtA in comparison with those fed only a honey solution. Mean longevity was significantly prolonged when parasitoids were fed a honey solution and BtA–honey solution in comparison with those fed BtA–distilled water, distilled water, or nothing. There were no significant differences compared with the control in any biological characteristics for the offspring of female parasitoids fed the honey solutions containing BtA at concentrations of 50, 100, and 200 μg ml−1; characteristics measured include the egg‐larval period, pupal weight, male and female pupal periods, adult fresh weight, and adult longevity. When female parasitoids parasitized host larvae that had been fed the diet containing BtA, their male and female pupal periods were significantly prolonged compared with the control (without BtA).

These investigations aimed to determine toxicity and bioefficacy of weed essential oils Bitter bush (Eupatorium odoratum L.), Finger grass (Limnophila aromatica (Lamk.) Merr.), and Vietnamese mint (Polygonum odoratum) derived by hydrodistillation against cowpea bruchids, Callosobruchus maculatus (Fabricius) on stored mungbean. Experiments were assessed under laboratory conditions (30±2°C, 70-80%RH and 16L:8D photoperiods). Results showed that weed essential oils from Bitter bush, Finger grass and Vietamese mint leaves have contact toxicity on cowpea bruchids as shown by the impregnated filter paper test. LC50 values were 137.15, 225.17 and 99.12 ppm at 48 h after exposure, respectively. Fumigant toxicity by the fumigation method on cowpea bruchids showed all weed essential oils had high efficiency against the cowpea bruchids (100% of mortality). Repellency toxicity test showed that weed essential oils from Bitter bush, Finger grass and Vietnamese mint leaves have repellent toxicity on cowpea bruchids as LC50 values were 607.23, 141.93 and 109.81 ppm at 6 h after exposure, respectively. The potential of weed essential oils on reproduction of the cowpea bruchids female adults had strong repellent activity for egg laid on mungbean seeds, were 100% at 48 h. Three weed essential oils did not affect the seed germinating. These results suggested that essential oils from three weed plants could be used as potential control agents for cowpea bruchids, and the database can be used for active ingredient studies to develop commercial products in the future.

Cowpea bruchids is one of the most important insect pests in stored products, especially of whole grains used for breeding or consumption. Currently, synthetic insecticides cause adverse effects to human health and the environment, thus new alternative biopesticides from herb or plant are needed for cowpea bruchids control. The aim of this research was to evaluate insecticidal activities of essential oil from Indian borage, Plectranthus amboinicus. Efficacy of this essential oil against C. maculatus was investigated by impregnated filter paper and vapor-phase tests. Experiments were conducted under Completely Randomized Design (CRD) with 4 replications. Contact activity was considered on essential oil at 6 concentrations of 0 300 600 900 1,200 and 1,500 ppm and fumigant activity was performed at 6 concentrations including 0 3 6 9 12 and 15 µL/L air. All experiments were assessed under laboratory conditions (30±2ºC, 70-80%RH and 16L:8D photoperiods). Data of deaths cowpea bruchids were recorded after treated at 24 to 168 h. Contact activity showed 1,200 ppm of P. amboinicus essential oil at 168 h was the best performance in the contact toxicity on cowpea bruchids and fumigation activity presented 12 µL/L air of P. amboinicus essential oil at 72 h had the highest effectiveness in the fumigation toxicity on cowpea bruchids, with 100% adult mortality. The data pointed that P. amboinicus essential oil showed the high potential for insecticidal activity for cowpea bruchids control. Hence, the essential oil of P. amboinicus might be used as an alternative for grain protection against stored-product insects.