During storage, beans can be infested with many insect-pests including Zabrotes subfasciatus, a key pest of these crops. This study aimed to identify bean genotypes demonstrating antixenosis and/or antibiosis to Z. subfasciatus and to test their integration with chemical control. The ultimate goal of assessment was to distinguish whether genotypic and insecticidal factors can provide effective beetle control. The tested genotypes were (a) Phaseolus vulgaris group: CCB, BSCB, BCB and PCB; (b) Vicia faba group: YBB, WBB and SBB; and (c) Vigna unguiculata group: C and GC. Initial assays were run to select genotypes (without insecticide treatment) that would be further tested with insecticides. Final assays included genotypes with varying degree of antibiosis and antixenosis treated with a neem formulation (Natuneem®) and distilled water (control) plus deltamethrin (Decis®) which latter was used only in the final antibiosis assay. The insecticides were used at the rates of 3 and 0.1 mL of Natuneem® and Decis®, respectively, per 30 mL of distilled water. There were no differences in preference of Z. subfasciatus adults among non-treated genotypes (initial assays), although neem-treated genotypes altered the preference and reduced infestation from 40.54-100% (final assays). In antibiosis tests, oviposition and density of emerged adults were reduced among C and SBB, and SBB also reduced the weight of emerged adults. Insecticides reduced oviposition in 53-100% and yielded half to five-fold fewer emerging insects weighting 35%-40% less in antibiotic genotypes. SBB was the most antibiotic genotype and this and other genotypes possessing antibiosis had a synergistic effect with neem or deltamethrin.

The advent of genetically modified crops expressing insecticidal proteins of the bacterium Bacillus thuringiensis (Bt) revolutionized the management of insect pest species. Nonetheless, such disruption does not come free from controversies and concerns. The quick spread of Bt resistance in targeted pest species is an example, and the impact in non‐targeted arthropod species is another. The former is a continuous focus of attention, while the latter faces knowledge gaps and methodological shortcomings particularly when arthropod communities are concerned. If Bt crops such as cotton are aimed at drastically reducing a key community component, such as targeted caterpillars in the Neotropical region, a significant community‐level impact is expected and deserves assessment. However, the subject is neglected with existing studies focusing on arthropod assemblages or low‐level taxa compromising their resolution. Thus, food web analysis was used here to assess the short‐term impact of Bt cotton on the associated arthropod community in a Neotropical scenario. Bt cotton and related non‐Bt cotton were cultivated for two years, and the arthropods were sampled using sweep net and whole plant collections throughout the cotton phenological cycle. The gathered data were used to build (plant–consumer–predator) trivariate networks using food web analysis. Thirty‐six arthropod species were sampled with the prevalence of whiteflies, cotton aphids, boll weevils and green leafhoppers, the main pest species in the region. Cotton genotype and cultivation year significantly affected the abundance and diversity of the associated arthropod assemblage (Fapp ≥ 2.86, p < 0.01). However, the Bt cotton‐associated food webs were similar to those of the non‐Bt cotton, indicating no significant impact of this technology on arthropod food webs. This result would be welcome, if it not indicating that Bt cotton did not provide a significant control of the main target pest species of the crop raising questions on the usefulness of the technology in the area.

A standardized sampling plan is the starting point for developing a decision‐making system for pest control. Aphis gossypii (Hemiptera: Aphididae) is a destructive sap‐feeding pest on cotton worldwide. However, research addressing cotton cultivar, plant phenology and field size with the aim of developing a sampling plan for A. gossypii has not been done. Therefore, in this study, we developed a standardized sampling for A. gossypii as a function of these factors. To accomplish this, A. gossypii densities in four experimental cotton cultivars were sampled weekly during year one to determine the ideal aphid characteristic to sample (by individual or colony). During year one and two, A. gossypii densities were sampled weekly in the same cultivars to determine sampling unit, sampling technique and the number of samples for an A. gossypii sampling plan. Using the sample number determined, the sampling time was recorded for cotton field size of 1, 5, 10, 50, 100 and 150 ha in order to estimate the sampling cost. In cotton, the count of individuals was the best characteristic for the assessment of A. gossypii. Leaves of the most apical branches for the vegetative and reproductive cotton plant stage were the best sampling units. The best sampling technique was direct counting. The cotton cultivar did not affect the development of the sampling plan. The A. gossypii sampling plan involved the evaluation of 58 samples per zone and required 20 min (<0.35 min/sample) for the evaluation of these samples. However, the walking time between samples was the main factor responsible for the total sampling time and cost in cotton fields, and this factor strongly depends on the size of the cotton field.

Maize is attacked by various pest species, including the key-pest of stored maize, Sitophilus zeamais (Coleoptera: Curculionidae). This study determined the LC50 and LD50 of neem-based insecticides (AzaMax® and Natuneem®) in comparison to a synthetic pyrethroid insecticide (Decis® 25 CE) to S. zeamais. The bioassays consisted of insects’ exposure alone (topical application with microsyringe) and exposure of both insects and seeds treated simultaneously. The final bioassays used four to six concentrations of each formulation per bioassay, diluted in distilled water. The bioassays were run with the use of 10 non-sexed adults of S. zeamais per replication and mortality was assessed after 48 h of exposure. The data regarding concentration and dose-mortality were analyzed by probit analysis. Both LC50 and LD50 were used to calculate LCR and LDR’s and their respective confidence interval (CI). After using topical application, the bioassays yielded LD50-values of 51.32, 76.76 and 42.75 μL of AzaMax, Natuneem and Decis/g of insects, respectively. The bioassays with simultaneous exposure of both insects and seeds yielded LC50-values of 4.01, 4.46 and 0.41 μL of AzaMax, Natuneem and Decis/g of seeds, respectively. Regarding the fact that there were no significant differences between the LC50-values of the botanical insecticides, both of them can be used to manage S. zeamais infesting stored corn. The cost to treat maize and to obtain effective control of S. zeamais is cheapest for Decis<Natuneem<Azamax. The LC50-values found in our study would be equivalent to use 8.02, 8.92 and 0.82 L of AzaMax, Natuneem and Decis/ton of seeds.

The boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), is one of the key pests and limiting factors to cotton production in conventional and organic systems. We assessed the use of resistant and susceptible cotton cultivars, a neem-based insecticide (Natuneem), and trapping with an A. grandis grandis aggregation pheromone as possible control tactics. In the first of two growing seasons we evaluated resistance of colored fiber cotton cultivars BRS 200, BRS Rubi, BRS Safira, and BRS Verde, and white fiber cotton BRS Aroeira, against A. grandis grandis attack. In the second growing season we assessed three colored cotton cultivars grown in and without close association of BRS Aroeira, and two control tactics: the neem-based pesticide and trapping. Because BRS Aroeira showed resistance against A. grandis grandis in the first growing season, it was selected to be planted in close association with more susceptible colored cultivars in the second growing season. Field plots with white and colored cotton cultivars reduced the need to control A. grandis grandis using the neem-based pesticide. Control by the neem-based pesticide and by trapping were of comparable value although the traps provided measurable control during early cotton growth stages and the neem-based pesticide provided measurable control during later cotton growth stages.