RESUMO: Avaliamos em condições de campo a toxicidade de inseticidas previamente identificados como nocivos em bioensaios de laboratório e semicampo sobre o parasitóide Trichogramma pretiosum (Hymenoptera: Trichogrammatidae). Os experimentos foram conduzidos durante as safras 2019/20 e 2020/21 em lavouras de arroz. Seguindo as recomendações da International Organization for Biological and Integrated Control (IOBC), quatro inseticidas foram aplicados em parcelas experimentais de 64 m2. Posteriormente, realizou-se uma liberação inundativa de T. pretiosum. Para verificar as taxas de parasitismo, aos 1, 2, 4 e 6 dias após a liberação (DAR) dos parasitoides, ovos do hospedeiro Ephestia kuehniella (Lepidoptera: Pyralidae) foram ofertados. Após a determinação do número de ovos parasitados, os dados foram agrupados em um coeficiente de redução (Ex) para fornecer um resultado único para os efeitos dos inseticidas sobre o parasitoide. Tanto para as safras 2019/20 quanto 2020/21, verificou-se que em 2 DAR, ocorreram as maiores taxas de parasitismo. Em contraste, aos 6 DAR, não foram observadas taxas de parasitismo. Lambda-cialotrina, tiametoxam e zeta-cipermetrina foram classificados como moderadamente nocivos; tiametoxam + lambda-cialotrina foi classificado como prejudicial. Seguindo as diretrizes da IOBC, a toxicidade desses produtos em condições de campo é inferior à obtida em laboratório ou semi-campo para o T. pretiosum. Entretanto, esses inseticidas devem ser evitados, ou utilizados em momentos que não coincidam com a liberação ou presença do parasitoide a campo.

ABSTRACT: We evaluated under field conditions the toxicity of insecticides previously identified as harmful in laboratory and semifield bioassays on the parasitoid Trichogramma pretiosum (Hymenoptera: Trichogrammatidae). The experiments were conducted during the 2019/20 and 2020/21 harvests in rice fields. Following the recommendations of the International Organization for Biological and Integrated Control (IOBC), four insecticides were applied in 64 m2 experimental plots. Subsequently, T. pretiosum was released inundatively. To verify parasitism rates, at 1, 2, 4 and 6 days after release (DAR) of the parasitoids, eggs from the host Ephestia kuehniella (Lepidoptera: Pyralidae) were offered. After determining the number of parasitized eggs, the data were grouped into a reduction coefficient (Ex) to provide a single result for the effects of the insecticides on parasitoid. For both the 2019/20 and 2020/21 evaluated crops, it was found that at 2 DAR, the highest parasitism rates occurred. In contrast, in 6 DAR, no parasitism rates were observed. Lambda-cyhalothrin, thiamethoxam, and zeta-cypermethrin were classified as moderately harmful; thiamethoxam + lambda-cyhalothrin was classified as harmful. Following IOBC guidelines, the toxicity of these products under field conditions is lower than that obtained in the laboratory or semi-field for the T. pretiosum. However, these insecticides should be avoided, or used at times that do not coincide with the release or presence of the parasitoid in the field.

Abstract In addition to destroying the leaves, stems, pods, and grains of soybean (Glycine max), Spodoptera frugiperda larvae may also have the cut off behavior in the seedlings close to the ground, harming the establishment of the soybean crop. Therefore, this study aimed to evaluate the consequences of the fall armyworm attack by adopting the cut off behavior, which has been similarly documented for black cutworm (Agrotis ipsilon) in newly emerged soybean plants. The treatments were five levels of infestation with 0, 5, 10, 20 and 40 larvae per m2. Three variables were assessed: (1) stand (relationship between attacked and initial number of plants), (2) types and amounts of injured structures, such as hypocotyl (embryonic shoot), and the cotyledons (seed leaves), and (3) level of defoliation. The variables were collected every 24 hours until the pupal stage. Additionally, the final stand of the seedlings was quantified, with the highest injury intensity observed in the plots that contained the highest number of larvae. In the second experiment, the dynamics of movement and attacks of plants by S. frugiperda larvae at the following times of the day: 07:00, 10:00, 13:00, 16:00, 19:00 and 21:00 were analyzed with supervised machine learning models. The injury caused by S. frugiperda with the behavior of the cut off and the voracity of the larvae were evident in the structures (hypocotyl and cotyledons) of the evaluated plants. The results of the present study emphasize the need to manage S. frugiperda during the preplanting phase of soybean.

La fertilidad del suelo con fuentes de azufre se presenta como una herramienta importante para ser incorporada en el manejo de las plagas. Este mineral puede conferir tolerancia o mortalidad a los insectos. En este estudio se evaluaron fuentes de azufre sobre la dinámica poblacional de Scaptocoris castanea (Hemiptera: Cydnidae) y sus efectos en las plantas de algodón. El experimento tuvo un diseño factorial resultante de la combinación de cuatro dosis de sulfato de calcio (CaSO4) y cuatro dosis de sulfato de amonio [(NH4)2SO4)]. No hubo correlación entre la humedad del suelo (%) y la infestación de insectos (%) (ninfas + adultos), excepto para el tratamiento sin sulfato de calcio (0 kg/ha) con 208 kg/ha de sulfato de amonio. Hubo una diferencia significativa entre la infestación media y anterior de S. castanea con la aplicación de sólo 1.500 kg/ha de sulfato de calcio. La relación entre el rendimiento de algodón (kg/ha) y sulfato de amonio fue mejor descrita por una función cúbica a las concentraciones 750, 1.125 y 1.500 kg/ha de sulfato de calcio.Para esta relación, sólo en ausencia de sulfato de calcio, se describe una función lineal de mejor ajuste. Las fuentes de azufre influyeron en la apariencia visual de las plantas dado que se encontró una cantidad más grande de plantas con lesiones y/o reducción del tamaño en los tratamientos control (sin fuentes de azufre). Los resultados de esta investigación refuerzan el planteamiento de que las fuentes de azufre pueden ser útiles en la implementación de programas de control de S. castanea en algodón.

Soil fertility with sulphur sources is an important tool that can be used in the management of pests. Sulphur can induce tolerance or even cause mortality to insect pests. This study evaluated the application of sulphur sources on the population dynamics of Scaptocoris castanea (Hemiptera: Cydnidae) and its effects on cotton plants. The experiment had a factorial design consisting of a combination of four concentrations of calcium sulfate (CaSO4) and four concentrations of ammonium sulphate [(NH4)2SO4]. There was no correlation between soil humidity (%) and insect infestation (%) (nymphs + adults), except for the treatment without calcium sulfate (0 kg/ha) along with 208 kg/ha of ammonium sulfate. There was a significant difference between average and previous infestation of S. castanea with the application of only 1,500 kg/ha of calcium sulfate. The relationship between cotton yield (kg/ha) and ammonium sulfate was best described by a cubic function at concentrations of 750, 1,125 and 1,500 kg/ha of calcium sulfate; on the other hand, a linear function was best adjusted in the absence of calcium sulfate. Sulphur sources influenced the visual appearance of the plants as many plants were found with injuries and/or were reduced in size in those treatments without application of any sulphur sources. These results reinforce the idea that suphur sources may be useful in the management of S. castanea on cotton.

O efeito de diferentes densidades (1, 3, 5, 7 e 9) de 3º lagartas do instar de Alabama argillacea (Huebner) no consumo de alimento por machos de Podisus nigrispinus (Dallas) foi avaliado em condições de laboratório. As densidades utilizadas foram convertidas a peso de presa oferecida: 13,40 mg (1 lagarta), 33.30 mg (3 lagartas), 54,30 mg (5 lagartas), 81,80 mg (7 lagartas) e 110,34 mg (9 lagartas). A quantidade de alimento consumido pelo macho de P. nigrispinus aumentou com a densidade da presa. A densidade da presa não afetou o tempo gasto pelo predador para ingerir o alimento. A quantidade de alimento extraído por minuto pelo predador foi sempre maior nas mais baixas densidades e menores nas mais altas densidades. O peso corpóreo médio dos machos de P. nigrispinus não difereriu entre os tratamentos testados e o seu ganho de peso foi menor nas duas primeiras densidades testadas. As taxas de consumo relativo aumentaram com a quantidade de lagartas oferecidas. Os machos de P. nigrispinus podem mudar seu comportamento predatório em função da quantidade de presas disponíveis.

In this work, the effect of different densities (1, 3, 5, 7 and 9) of 3rd instar Alabama argillacea (Huebner) larvae on food consumption by Podisus nigrispinus (Dallas) males was evaluated. The densities established were converted to weight of prey offered: 13.4 mg (one larva), 33.3 mg (three larvae), 54.3 mg (five larvae), 81.8 mg (seven larvae), and 110.34 mg (nine larvae). The quantity of food consumed by P. nigrispinus increased with the prey density. The density of preys did not affect the time spent by the predator to ingest the food. The quantity of food extracted per minute was always higher in smaller densities and lower in higher densities. Males mean body weight did not differ statistically between the treatments tested, and weight gain was smaller in the first two densities tested. Relative consumption rates increased with the quantity of larvae offered. P. nigrispinus males might change its predatory behavior as a function of the quantity of prey available.

Estudou-se o efeito estimulatório de baixas concentrações de gamacihalotrin sobre Podisus nigrispinus (Dallas)(Heteroptera: Pentatomidae). As doses de gamacihalotrin estudadas foram: 23,4375, 11,7188, 5,8594, 2,9297, 1,4648, 0,7324 mg.litro-1 e água (controle). Todas as doses estudadas de gamacihalotrin reduziram o período de desenvolvimento do 3º, 4º e 5º ínstares de P. nigrispinus. A sobrevivência e a longevidade do predador foram mais altas quando foi exposto a baixas doses. O período de oviposição de P. nigrispinus reduziu á medida que foram aumentadas as doses de gamacihalotrin. A dose de 11,7188 mg.litro-1 de gamacihalotrin causou os mais curtos períodos de pré-oviposição e pós-oviposição. O intervalo entre posturas aumentou com a dose de 0,7324 mg.litro-1 de gamacihalotrin. A viabilidade de ovos não foi afetada pelo piretróide. O número de ovos por postura, posturas por fêmea, período de incubação e peso corpóreo de fêmea não foram afetados pelas doses testadas de gamacyhalotrin.

Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) was exposed to gammacyhalothrin to study the stimulatory effect of low concentrations of this pyrethroid. The doses studied were 23.4375, 11.7188, 5.8594, 2.9297, 1.4648, 0.7324 mg.litre-1 and water, as control. The third, fourth, and fifth instars of P. nigrispinus were shorter with all the doses of this insecticide. The survival and longevity of this predator was highest with the lowest doses. The oviposition period of P. nigrispinus decreased as the doses increased. The lowest pre-and postoviposition periods were found with 11.7188 mg.litre-1 of gammacyhalothrin. The dose 0.7324 mg.litre-1 increased the clutch interval. The egg viability was similar between the treatments. The number of eggs per clutch, clutches per female, incubation period, and female body weight were not affected. The hormesis response could be used as a tool for IPM programs, allowing the manipulating parameters of this predator in synergism with this insecticide.