The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a widespread pest species of various cultivated plants. The pest status of FAW in cotton in the Cerrado region of Brazil has increased with the recent changes in cotton crop systems, such as double cropping and the use of cover or winter crops with non‐tillage cropping systems. In this study we investigated the performance of FAW on three major crops cultivated in the Cerrado – soybean, corn, and cotton – and millet which has been integrated into the landscape as a cover crop. Further, the damage to various reproductive structures of cotton plants by FAW larvae was determined. Both studies were conducted under field conditions. Survival of FAW larvae caged on millet plants was higher than on other hosts. The FAW reared on millet also exhibited a net reproductive rate similar to that observed on corn, which was considered the best host for FAW, and the highest intrinsic rate of increase and lowest mean generation time compared to all other hosts. In cotton, the low availability of bolls during the plant’s blooming stage resulted in higher square feeding, whereas infestation during the plant’s boll stage resulted in higher loss of bolls and lower attack on squares. The number of adults produced in a generation was higher when plants were infested in the boll stage. The results indicated that FAW is a threat to cotton when bolls are available and can cause significant loss of reproductive structures. In addition, based on the FAW performance feeding on millet, this cover crop can be among the reasons of FAW increasing pest status in subsequent crops.

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Tritrophic interactions (plant-herbivorenatural enemy) are basic components of nearly all ecosystems, and are often heavily shaped by bottom-up forces. Numerous factors influence plants' growth, defense, reproduction, and survival. One critical factor in plant life histories and subsequent trophic levels is nitrogen (N). Because of its importance to plant productivity, N is one of the most frequently used anthropogenic fertilizers in agricultural production and can exert a variety of bottom-up effects and potentially significantly alter tritrophic interactions through various mechanisms. In this paper, the potential effects of N on tritrophic interactions are reviewed. First, in plant-herbivore interactions, N availability can alter quality of the plant (from the herbivore's nutritional perspective) as food by various means. Second, nitrogen effects can extend directly to natural enemies through herbivores by changes in herbivore quality vis-à-vis the natural enemy, and may even provide herbivores with a defense against natural enemies. Nitrogen also may affect the plant's indirect defenses, namely the efficacy of natural enemies that kill herbivores attacking the plant. The effects may be expressed via (1) quantitatively and/or qualitatively changing herbivore-induced plant volatiles or other plant features that are crucial for foraging and attack success of natural enemies, (2) modifying plant architecture that might affect natural enemy function, and (3) altering the quality of plant-associated food and shelter for natural enemies. These effects, and their interactive topdown and bottom-up influences, have received limited attention to date, but are of growing significance with the need for expanding global food production (with accompanying use of fertilizer amendments), the widening risks of fertilizer pollution, and the continued increase in atmospheric CO 2 .

A number of cotton varieties have been genetically transformed with genes from Bacillus thuringiensis (Bt) to continuously produce Bt endotoxins, offering whole plant and season-long protection against many lepidopteran larvae. Constant whole-plant toxin expression creates a significant opportunity for non-target herbivores to acquire and bio-accumulate the toxin for higher trophic levels. In the present study we investigated movement of Cry1Ac toxin from the transgenic cotton plant through specific predator-prey pairings, using omnivorous predators with common cotton pests as prey: (1) the beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), with the predator Podisus maculiventris (Heteroptera: Pentatomidae); (2) the two-spotted spider mite, Tetranychus urticae (Acarina: Tetranychidae), with the predatory big-eyed bug Geocoris punctipes (Heteroptera: Geocoridae) and (3) with the predatory damsel bug Nabis roseipennis (Heteropera: Nabidae); and (4) the thrips Frankliniella occidentalis (Thysanoptera: Thripidae) with the predatory pirate bug Orius insidiosus (Heteroptera: Anthocoridae). We quantified Cry1Ac toxin in the cotton plants, and in the pests and predators, and the effects of continuous feeding on S. exigua larvae fed either Bt or non-Bt cotton on life history traits of P. maculiventris. All three herbivores were able to convey Cry1Ac toxin to their respective predators. Among the herbivores, T. urticae exhibited 16.8 times more toxin in their bodies than that expressed in Bt-cotton plant, followed by S. exigua (1.05 times), and F. occidentalis immatures and adults (0.63 and 0.73 times, respectively). Of the toxin in the respective herbivorous prey, 4, 40, 17 and 14% of that amount was measured in the predators G. punctipes, P. maculiventris, O. insidiosus, and N. roseipennis, respectively. The predator P. maculiventris exhibited similar life history characteristics (developmental time, survival, longevity, and fecundity) regardless of the prey's food source. Thus, Cry1Ac toxin is conveyed through non-target herbivores to natural enemies at different levels depending on the herbivore species, but continuous lifetime contact with the toxin by the predator P. maculiventris through its prey had no effect on the predator's life history. The results found here, supplemented with others already published, suggest that feeding on Cry1Ac contaminated non-target herbivores does not harm predatory heteropterans and, therefore, cultivation of Bt cotton may provide an opportunity for conservation of these predators in cotton ecosystems by reducing insecticide use.

1 Studies have shown that Cry proteins of the bacterium Bacillus thuringiensis expressed in transgenic plants can be acquired by nontarget herbivores and predators. A series of studies under field and controlled conditions was conducted to investigate the extent to which Cry1Ac protein from Bt transgenic cotton reaches the third trophic level and to measure the amount of protein that herbivores can acquire and expose to predators. 2 Levels of Cry1Ac in Bt cotton leaves decreased over the season. Among herbivores (four species), Cry1Ac was detected in lepidopteran larvae and the amount varied between species. Among predators (seven species), Cry1Ac was detected in Podisus maculiventris and Chrysoperla rufilabris . 3 In the greenhouse, only 14% of the Cry1Ac detected in the prey ( Spodoptera exigua larvae) was subsequently found in the predator P. maculiventris. Detection of Cry1Ac protein in Orius insidiosus , Geocoris punctipes and Nabis roseipennis was probably limited by the amount of prey consumed that had fed on Bt cotton. 4 Purified Cry1Ac was acquired by the small predatory bug G. punctipes but at much higher concentration than found in plants or in lepidopteran larvae. 5 Bt protein was shown to move through prey to the third trophic level. Predatory heteropterans acquired Cry1Ac from prey fed Bt cotton, but acquisition was dependent on the concentration of Cry1Ac conveyed by the prey and the amount of prey consumed. The type and availability of prey capable of acquiring the protein, coupled with the generalist feeding behaviour of the most common predators in the cotton ecosystem, probably constrain the flow of Cry1Ac through trophic levels.In the laboratory, a study of ingestion of various dosages of Bt protein was conducted using adult G. punctipes to verify the ability of this predatory heteropteran to ingest Cry1Ac 194 J. B. Torres et al.

The kudzu bug or bean plataspid, Megacopta cribraria (Fabricius), is native to Asia where it appears to be widely distributed (although the taxonomy is not entirely clear), but is Hemisphere. Other natural enemies may eventually emerge as good candidates for importation, but at present P. saccharalis appears to be most promising.

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Nitrogen (N) is one of the most critical chemical elements for plant and animal growth, exerting a variety of bottom‐up effects. Development and oviposition of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), were studied in relation to varying N fertilization levels (42, 112, 196, and 280 p.p.m.) in cotton [Gossypium hirsutum L. (Malvaceae)]. Low N fertilization of cotton plants led to reduced plant biomass and a lower percentage of N in leaf blades and in leaf petioles. Development of S. exigua larvae fed with plants with reduced N applications (42 and 112 p.p.m.) was prolonged relative to treatments receiving higher N fertilization. Almost all larvae reared on artificial diets underwent only five instars before pupation. However, most larvae reared on cotton plants, irrespective of N levels, experienced a supernumerary sixth larval instar. Furthermore, significantly more larvae reared on lower N cotton plants underwent supernumerary development compared to larvae reared on higher N cotton plants. Life‐time feeding damage per larva ranged from 55 to 65 cm2, depending on the nutritional quality of the food plant, although the differences were not statistically significant. Larvae distinguished between cotton plants with various nutritional qualities and fed preferentially on higher N plants. Female moth oviposition choice was also affected by host plant nutritional quality: cotton plants with higher N levels were preferentially chosen by S. exigua females for oviposition. The mechanisms of these effects are unclear, but they can have important implications for population dynamics and pest status of beet armyworms in the field.