The marked adoption of bioinsecticides in Brazilian agriculture in recent years is, at least partially, explained by the increasingly higher levels of insect pest resistance to synthetic insecticides. In particular, several baculovirus-based products have been registered in the last 5 years, including Helicoverpa armigera nucleopolyhedrovirus (HearNPV: Baculoviridae: Alphabaculovirus (Armigen^®)). Understanding the susceptibility of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) to HearNPV is an important step toward development of robust Integrated Pest Management (IPM) and Insect Resistance Management programs (IRM) aimed at managing this serious insect pest. In this study, droplet feeding bioassays were used to characterize the baseline susceptibility to HearNPV (Armigen^®) in H. armigera populations collected from major soybean and cotton-growing regions in Brazil. We defined and validated a diagnostic concentration for susceptibility monitoring of H. armigera populations to HearNPV. Additionally, cross-resistance between HearNPV and the insecticides flubendiamide and indoxacarb was evaluated by testing HearNPV in a susceptible strain and in resistant strains of H. armigera to these insecticides. A low interpopulation variation of H. armigera to HearNPV was detected. The LC₅₀ values ranged from 1.5 × 10⁵ to 1.1 × 10⁶ occlusion bodies (OBs) per mL (7.3-fold variation). The mortality rate at the identified diagnostic concentration of 6.3 × 10⁸ OBs/mL, based on the calculated LC₉₉, ranged from 98.6 to 100% in populations of H. armigera collected from 2018 to 2020. No cross-resistance was detected between HearNPV and flubendiamide or indoxacarb. These results suggest that HearNPV (Armigen^®) can be an effective tool in IPM and IRM programs to control H. armigera in Brazil.

Helicoverpa armigera caterpillars are polyphagous and exhibit high migratory potential. Given the traits of this pest, alternative hosts located in or near the crop stand may support the survival and permanence of H. armigera in the field. The aim of this study was to investigate Conyza sp. as a food source for H. armigera caterpillars in scenarios with conventional and Bt soybean. Two experiments were conducted in biochemical oxygen demand incubators. The first assessed consumption of conventional soybean, Bt soybean and Conyza sp. leaves by 3rd and 5th instar caterpillars, with no choice given (no-choice test). The second test evaluated the food preference of 3rd instar H. armigera larvae, with two choices given (dual-choice test). Fifth instar larvae favored Conyza sp. leaves to Bt soybean, but preferred conventional soybean to both of these options. The survival of 3rd instar caterpillars did not differ statistically regardless of the plant species used as a food source. Fifth instar larvae fed Bt soybean exhibited lower survival rates when compared to Conyza sp. and conventional soybean. In dual-choice test arenas, soybean leaf consumption was superior to Conyza sp. Conventional soybean consumption was also greater when offered in conjunction with Bt soybean. Caterpillars offered Conyza sp. and Bt soybean leaves only consumed the weed species. Conyza sp. plants can serve as a food source for H. armigera larvae, which showed a preference for Conyza sp. leaves to Bt soybean.

This study aimed to evaluate the effect of different managements with pig slurry (PS) and cattle slurry (CS) on wheat dry matter and grain yields, and the potential to estimate this variation with the NDVI (normalized difference vegetation index) and NDRE (normalized difference red edge index) vegetation indices. The experiment was conducted in Frederico Westphalen-RS, Brazil, in a randomized block experimental design, in a 2 x 7 factorial scheme with four replicates and seven forms of surface and subsurface application, with and without the use of the dicyandiamide (DCD) nitrification inhibitor, distributed as follows: control without application of slurry and DCD; control without application of slurry and DCD, but scarified only with the injection machine; surface application; surface application with DCD; subsurface injection; subsurface injection with DCD; and application of NPK in mineral form. At flowering of the wheat crop, dry matter was collected and readings of NDVI and NDRE were taken, and finally grain yield was quantified. For PS and CS, best results of dry matter and grain yields were found in managements with subsurface injection and subsurface injection with DCD, respectively. Among the vegetation indices, only NDVI was efficient to estimate variations in the management using CS for wheat dry matter and grain yields.

The objective of this study was to evaluate the influence of adjuvants associated with the spray mixture of insecticides aimed at the control of Euschistus heros in the soybean crop. First the treatments were applied and later the cages were assembled, being artificially infested 10 insects per cage. The treatments were composed of the insecticide Engeo Pleno® in combination with different adjuvants. The surface tension was reduced in all the treatments that contained the addition of adjuvants, and the treatments with organosilicone were the ones that resulted in the lower levels. The treatments did not present a significant difference, however, a superior efficiency of the insecticide was observed in association with adjuvants. The addition of Assist®, Break Thru® S240 and TA35® adjuvants to the thiamethoxam + lambda-cyhalothrin insecticide improves the control of Euschistus heros, showing an agronomic efficiency superior to the insecticide applied alone.

Entre os diversos testes de controle de qualidade de sementes, o de condutividade elétrica tem grande potencial para determinar a qualidade delas com rapidez e confiabilidade. Devido à escassez de informações na literatura referentes à metodologia do teste de condutividade elétrica para sementes de painço, neste trabalho o objetivo foi avaliar o teste de condutividade elétrica, considerando períodos de embebição, volumes de água e número de sementes, buscando estabelecer a metodologia mais adequada para a estratificação de lotes. O trabalho envolveu três experimentos: caracterização dos lotes; determinação do número de sementes x volumes de água à ser utilizado (25, 50, 75 e 100 sementes e 25, 50, 75 e 100 ml de água) e período de condicionamento (2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 e 24 horas). Na caracterização, os lotes 1 e 4 foram definidos como os mais vigorosos entre todos avaliados. O teste de condutividade elétrica é eficiente para avaliação do potencial fisiológico de lotes de sementes de painço, sendo a estratificação possível utilizando-se 25 sementes, embebidas em 50 ml de água deionizada, por um período de 14 horas.