Resumen Las chinches son consideradas importantes plagas de la soya al causar daños que afectan su producción y comercialización. La determinación de los umbrales de acción para el control de estas plagas garantiza una mayor seguridad en el uso de insecticidas. El objetivo de este estudio fue evaluar el umbral de acción en el manejo de las chinches de la soya y su influencia en los parámetros fitotécnicos y fisiológicos y en el parasitismo de huevos de las chinches. El experimento se instaló en campo, en bloques al azar, utilizando el cultivar Anta 82 RR. Los tratamientos tuvieron cinco umbrales de acción para las chinches fitófagas: 0,5 chinches/m, 1,0 chinche/m, 2,0 chinches/m, 4,0 chinches/m y el control (sin aplicación de insecticidas), con cuatro repeticiones. El muestreo de las chinches se llevó a cabo a través del método del paño vertical y para evaluar el parasitismo se realizaron muestreos semanales de los huevos de las chinches. Los parámetros fisiológicos y fitotécnicos que se evaluaron fueron los siguientes: productividad (kg/ha), peso de 100 semillas, índice de daño a las vainas (%), retención de la hoja, vigor, viabilidad y daño en las semillas. Se observó que los niveles de acción más severos contra chinches influenciaron positivamente en los parámetros fitotécnicos y fisiológicos de la soya, así como el número de semillas por vaina, semillas por planta y vainas por planta. Además el nivel de acción de 1,0 chinche/m es el más indicado para el tratamiento de los chinches de la soya; sin embargo, el parasitismo en este nivel de acción tiende a ser bajo.

Abstract Stink bugs are major soybean pests, causing damage that affects grain production and marketing. Determining action thresholds for pest control can improve the proper use of insecticides on these pests. This study aimed to evaluate five action thresholds for the management of stink bugs on soybeans, as well as their influence on phytotechnical and physiological parameters as well as on parasitism of stink bug eggs. This study was conducted in the field utilizing a completely randomized block design, using the soybean cultivar ‘Anta 82 RR’. Insecticide application treatments consisted of five action thresholds used against phytophagous stink bugs: half stink bug.m-1, one stink bug.m-1, two stink bugs.m-1, four stink bugs.m-1 and control (no insecticide sprayed), and four replications. Insect sampling was carried out using the beat cloth method, and parasitism evaluations were also taken weekly by conducting stink bug egg samplings. Soybean physiological and phytotechnical parameters, including crop yield (kg.ha-1), 100-seed weight, pod damage index PDI (%), leaf retention, plant vigor, seed viability and damage, number of seeds per pod, seeds per plant, and pods per plant were also assessed. It was observed that the most severe action thresholds used on stink bugs most positively influenced crop phytotechnical and physiological parameters. Moreover, it was noted that one stink bug.m-1 is the optimal action threshold for stink bug management on soybeans, even though egg parasitism at this level tended to be lower.

ABSTRACT The soybean looper Chrysodeixis includens is one of the main defoliating pests of soybean cultures in Brazil. This work aimed to evaluate the effect of offering different soybean genotypes to this insect to verify the occurrence of antixenosis. In a greenhouse, assays were carried out to determine the attractiveness of C. includens adults given free-choice tests. This experiment used a randomized block design with five replicates. A second experiment assessed oviposition preference using no-choice tests, employing a completely randomized design with five replicates. Seventeen soybean cultivars were used; several of these had previously been reported as carriers of resistance to more than one species of insect. In the laboratory, a morphological analysis was carried out by quantifying the number of trichomes on leaf surfaces and evaluating the color of the leaf blade of the germplasm. In the attractiveness assay, genotypes ‘IAC 19’, ‘IAC 18’, ‘IAC 23’, L1-1-01, PI 274453, PI 229358, PI 171451, ‘IAC 100’, ‘IAC 24’, ‘IAC 17’ and IAC 74-2832 were classified as repellents. In the oviposition preference experiment, PI 171451, PI 274453, ‘IAC 18’, L1-1-01 and ‘IAC 23’ showed the fewest eggs. The high density of trichomes presented by the genotypes PI 227687 and PI 274453 stand out as a possible C. includens resistance factor. The genotype L1-1-01 presented intermediate luminosity (L*) and more intense green (a*) and yellow (b*) colors compared to other genotypes. There was no correlation between oviposition and trichome density or leaf coloration.

O objetivo deste trabalho foi avaliar genótipos de feijoeiro quanto à resistência a lagarta-falsa-medideira (Chrysodeixis includens). Inicialmente, foram realizados testes com chance de escolha com 59 genótipos, divididos em três grupos, de acordo com a intensidade de coloração das folhas (verde-escura, verde-clara e verde-médio), para avaliar a preferência quanto à oviposição. Em seguida, selecionaram-se 12 genótipos com grande potencial de resistência, assim como dois padrões comerciais suscetíveis. Com estes genótipos, realizaram-se novos ensaios de oviposição, em casa de vegetação, além de testes de atratividade e consumo, em condições de laboratório (26±2ºC, 65±10% UR e fotófase de 14 h luz: 10 h escuro). No teste sem chance de escolha, com adultos, em casa de vegetação, os genótipos 'IAC Jabola', Arcelina 1, 'IAC Boreal', 'Flor de Mayo' e 'IAC Formoso' foram os menos ovipositados, tendo apresentado resistência do tipo antixenose à oviposição. No teste com chance de escolha, com larvas, Arcelina 4, 'BRS Horizonte', 'Pérola', H96A102-1-1-1-52, 'IAC Boreal', 'IAC Harmonia' e 'IAC Formoso' foram os genótipos menos consumidos, o que indica antixenose à alimentação. No teste sem chance de escolha, todos os genótipos (exceto 'IAPAR 57') expressaram níveis moderados de antixenose à alimentação de larvas de C. includens.

The objective of this work was to evaluate bean genotypes for resistance to soybean looper (Chrysodeixis includens). Initially, free-choice tests were carried out with 59 genotypes, divided into three groups according to leaf color intensity (dark green, light green, and medium green), in order to evaluate oviposition preference. Subsequently, 12 genotypes with high potential for resistance were selected, as well as two susceptible commercial standards. With these genotypes, new tests were performed for oviposition in a greenhouse, besides tests for attractiveness and consumption under laboratory conditions (26±2ºC, 65±10% RH, and 14 h light: 10 h dark photophase). In the no-choice test with adults, in the greenhouse, the 'IAC Jabola', Arcelina 1, 'IAC Boreal', 'Flor de Mayo', and 'IAC Formoso' genotypes were the least oviposited, showing antixenosis-type resistance for oviposition. In the free-choice test with larvae, Arcelina 4, 'BRS Horizonte', 'Pérola', H96A102-1-1-1-52, 'IAC Boreal', 'IAC Harmonia', and 'IAC Formoso' were the less consumed genotypes, which indicates antixenosis to feeding. In the no-choice test, all genotypes (except for 'IAPAR 57') expressed moderate levels of antixenosis to feeding against C. includens larvae.