The effect of different soybean varieties (Glycine max 356, M4, M7, M9, Clark, Sahar, JK, BP, Williams, L17, Zane, Gorgan3 and DPX) on the life history and fecundity of the gram pod borer Helicoverpa armigera (Hubner) (synonym Heliothis armigera (Hubner), also known as the American or African bollworm) was determined at 25 Ϯ 1°C, 65 Ϯ 5% r.h. and a light : dark cycle of 16:8 h. The larval period ranged 17.30 to 26.20 days on M7 and L17, respectively. The longest development time was on L17, BP and Sahar (42.71, 40.29 and 39.20 days, respectively) and the shortest was on M7, M9, Williams and Clark (34.21, 36.06, 36.60 and 36.82 days, respectively). The development index of overall immature stages varied from 1.39 to 2.41, with the minimum on L17 and BP and the maximum on M7. The highest daily fecundity and total fecundity (118.92 and 582.70 eggs, respectively) and the lowest (37.88 and 177.10 eggs, respectively) were observed on DPX and 356, respectively. Cluster analysis of the biological parameters of H. armigera on different soybean varieties demonstrated that BP, Sahar and L17 were partially resistant to H. armigera. Knowledge of the extent of susceptibility or resistance of crop varieties and biology of a pest on that crop are fundamental components of integrated pest management (IPM) programs for many crops. Such information can help to detect and monitor pest infestation, variety selection and crop breeding.

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Nutritional indices of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on different host plants including chickpea (cultivars Arman, Hashem, Azad, and Binivich), common bean (cultivar Khomein), white kidney bean (cultivar Dehghan), red kidney bean (cultivar Goli), cowpea (cultivar Mashhad), tomato (cultivar Meshkin) and potato (cultivars Agria and Satina) were studied under laboratory conditions (25 ± 1 °C, 65 ± 5% RH, 16:8 L:D). Third instar larvae reared on potato Agria showed the highest efficiency of conversion of digested food (ECD) and efficiency of conversion of ingested food (ECI) (50.800 é 0.104% and 13.630 ± 0.016%, respectively). Approximate digestibility (AD) values of the fourth instar larvae were highest (92.651 ± 0.004%) and lowest (57.140 — 0.049%) on chickpea Azad and potato Agria, respectively. The fifth instar larvae fed on tomato Meshkin and white kidney bean Dehghan had the highest consumption index (CI) (3.717 ± 0.091) and relative consumption rate (RCR) (1.620 ± 0.074), respectively. Whole larval instars showed the highest ECI and ECD values on potatoes Satina (14.640 ± 0.014%) and Agria (21.380 ± 0.015%), respectively, and the lowest of both values on tomato Meshkin (ECI: 5.748 ± 0.002% and ECD: 7.341 ± 0.002%). The results of nutritional indices and the cluster analysis indicated that tomato Meshkin was an unsuitable host for feeding of H. armigera.

The insect immune system is comprised of both humoral and cellular components that are mobilized in response to parasitic or pathogenic infections. Activation of the immune response implies a considerable expenditure of energy and that is why insects rely on inducible pathways that are activated after coming into contact with the pathogenic agent. Known as immune priming, insects can prolong the activation of the immune response and transmit their immune status to the next generation. Starting from a laboratory colony of the lepidopteran Spodoptera exigua and using the lytic zone assay as a measure of the immune status, we selected for a sub-colony with high levels of immune activity in the absence of external challenging with bacteria. Immune-activated insect showed characteristics that are typical reported for immune primed insects, such as increased tolerance to pathogens (Bacillus thuringiensis in our case), fitness-cost associated to the immune status, and maternal transmission of the immune status. However, additional analysis revealed that the selection for the immune-activated insects was based on the selection of insects carrying a higher bacterial load in the midgut. Our results suggest that activation of the immune system in S. exigua may not only occur as consequence of the immune priming but also from an increase in midgut microbiota load.