The host acceptance of neonate Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) larvae to Bt cotton plants exerts a strong influence on the potential risk that this pest will develop resistance to Bt cotton. This will also determine the efficiency of management strategies to prevent its resistance such as the “refuge-in-the-bag” strategy. In this study, we assessed the acceptance of neonate A. argillacea larvae to Bt and non-Bt cotton plants at different temperatures during the first 24 h after hatching. Two cotton cultivars were used in the study, one a Bt DP 404 BG (Bollgard) cultivar, and the other, an untransformed isoline, DP 4049 cultivar. There was a greater acceptance by live neonate A. argillacea larvae for the non-Bt cotton plants compared with the Bt cotton plants, especially in the time interval between 18 and 24 h. The percentages of neonate A. argillacea larvae found on Bt or non-Bt plants were lower when exposed to temperatures of 31 and 34°C. The low acceptance of A. argillacea larvae for Bt cotton plants at high temperatures stimulated the dispersion of A. argillacea larvae. Our results support the hypothesis that the dispersion and/or feeding behavior of neonate A. argillacea larvae is different between Bt and non-Bt cotton. The presence of the Cry1Ac toxin in Bt cotton plants, and its probable detection by the A. argillacea larvae tasting or eating it, increases the probability of dispersion from the plant where the larvae began. These findings may help to understand how the A. argillacea larvae detect the Cry1Ac toxin in Bt cotton and how the toxin affects the dispersion behavior of the larvae over time. Therefore, our results are extremely important for the management of resistance in populations of A. argillacea on Bt cotton.

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Intercropping is a traditional agronomic practice, and when properly managed, it can significantly contribute to pest control. The current study investigates the severity of plant damage related to infestation by the cotton aphid, Aphis gossypii Glover (Hemiptera: Heteroptera: Aphididae) and its predation by spotless ladybird beetle, Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae) and green lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) and parasitism by Lysiphlebus testaceipes (Cresson) (Hymenoptera: Aphidiidae) in sole cotton plots and in plots of cotton intercropped with fennel. Cotton aphid populations were significantly higher in sole cotton plots than in intercropping plots for plots that were not treated with insecticide. The percentages of losses in cotton seed yield were higher in the sole cotton plots than in the four intercropping systems (one row of cotton for two rows of fennel, one row of cotton for three rows of fennel, two rows of cotton for one row of fennel, and three rows of cotton for two rows of fennel). The losses in cotton seed yield were significantly lower in the intercropping system with three rows of cotton interspersed with two rows of fennel than in the other intercropping systems. Spotless ladybird beetle and green lacewing densities were significantly higher in the intercropping system with three rows of cotton interspersed with two rows of fennel than in the other intercropping systems. These results are of practical significance in designing appropriate strategies for cotton aphid control in cotton-fennel intercropping systems.

Studies on insect food intake and utilization are important for determining the degree of insect/plant association and host species’ resistance, and also for helping design pest management programs by providing estimates of potential economic losses, techniques for mass breeding of insects, and identifying physiological differences between species. We studied the feeding and development of fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), on transgenic (Bt) and non‐transgenic (non‐Bt) cotton. The larvae of S. frugiperda fed on Bt cotton had a longer development period (23.0 days) than those fed on non‐Bt cotton (20.2 days). Survivorship of S. frugiperda larvae fed on Bt cotton (74.1%) was lower than that of larvae fed on non‐Bt cotton (96.7%). Pupal weight of larvae fed on Bt cotton (0.042 g) was lower than that of larvae fed on non‐Bt cotton (0.061 g). The cotton cultivar significantly affected food intake, feces production, metabolization, and food assimilation by S. frugiperda larvae. However, it did not affect their weight gain. Intake of Bt‐cotton leaf (0.53 g dry weight) per S. frugiperda larva was lower than the intake of non‐Bt‐cotton leaf (0.61 g dry weight). Larvae fed on Bt‐cotton leaves produced less feces (0.25 g dry weight) than those fed on non‐Bt‐cotton leaves (0.37 g dry weight). Weight gain per S. frugiperda larva fed on Bt‐cotton leaves (0.058 g dry weight) was similar to the weight gain for larvae fed on non‐Bt‐cotton leaves (0.056 g dry weight). The cotton cultivar significantly affected the relative growth, consumption, and metabolic rates, as well as other nutritional indices: the figures were lower for larvae fed on Bt‐cotton leaves than for larvae fed on non‐transgenic cotton leaves.

In agroecosystems, parasitoids and predators may exert top-down regulation and predators for different reasons may avoid or give preference to parasitised prey, i.e., become an intraguild predator. The success of pest suppression with multiple natural enemies depends essentially on predator-prey dynamics and how this is affected by the interplay between predation and parasitism. We conducted a simple laboratory experiment to test whether predators distinguished parasitised prey from nonparasitised prey and to study how parasitism influenced predation. We used a host-parasitoid system, Spodoptera frugiperda and one of its generalist parasitoids, Campoletis flavicincta, and included two predators, the stinkbug Podisus nigrispinus and the earwig Euborellia annulipes. In the experiment, predators were offered a choice between non-parasitised and parasitised larvae. We observed how long it took for the predator to attack a larva, which prey was attacked first, and whether predators opted to consume the other prey after their initial attack. Our results suggest that, in general, female predators are less selective than males and predators are more likely to consume non-parasitised prey with this likelihood being directly proportional to the time taken until the first prey attack. We used statistical models to show that males opted to consume the other prey with a significantly higher probability if they attacked a parasitised larva first, while females did so with the same probability irrespective of which one they attacked first. These results highlight the importance of studies on predator-parasitoid interactions, as well as on coexistence mechanisms in agroecosystems. When parasitism mediates predator choice so that intraguild predation is avoided, natural enemy populations may be larger, thus increasing the probability of more successful biological control. Zusammenfassung In Agrarökosystemen können Parasitoide und Prädatoren 'top-down'-Kontrolle ausüben. Aus unterschiedlichen Gründen können Prädatoren parasitierte Beutetiere meiden oder präferieren. Der Erfolg der Schädlingskontrolle mit mehreren Antagonisten hängt entscheidend von der Räuber-Beute-Dynamik ab und davon, wie diese vom Wechselspiel zwischen Prädation und Parasitismus beeinflusst wird. Wir führten ein einfaches Laborexperiment durch, um zu prüfen, ob Räuber zwischen parasitierten und nicht parasitierten Beutetieren unterschieden und um zu untersuchen, wie Parasitierung die Prädation beeinflusste.