Spatio-temporal distribution of Anthonomus grandis grandis Boh. in tropical cotton fields.

BACKGROUND: Knowledge of the spatio-temporal distribution of pests is important for the development of accurate management approaches. The boll weevil, Anthonomus grandis grandis Boh., is a deleterious cotton, Gossypium hirsutum L., pest in the western hemisphere. The spread of boll weevils across cotton fields remains poorly understood. We assessed the dispersal pattern of adult weevils through cotton fields cultivated in a tropical area during dry and wet seasons using geostatistics for the number of adults and infested reproductive structures (buds, bolls and total). RESULTS: Adult weevils and infested reproductive structures increased across both seasons despite the prevailing climatic variables. In both seasons, boll weevil adults and infested reproductive structures followed an aggregated distribution. The distances over which samples maintained spatial dependence varied from 0.7 to 43.4 m in the dry season and from 6.0 to 614.4 m in the wet season. Boll weevil infestations started at field borders and the infested reproductive structures (oviposition and/or feeding punctured) were greater than the adults regardless of cotton growth stage. CONCLUSION: Sampling for boll weevils in cotton fields should start at the field borders and focus on total infested reproductive structures (buds + bolls) and as cotton plants develop, sampling should focus on the field as a whole. Distances among samples will vary from 6 to 470 m. Thus, despite the cotton phenological stage or growing season, monitoring of boll weevil should be done by sampling total infested reproductive structures with a minimum distance of 6 m among samples. © 2022 Society of Chemical Industry.

Cyantraniliprole susceptibility baseline, resistance survey and control failure likelihood in the coffee berry borer Hypothenemus hampei.

Cyantraniliprole was recently registered for controlling the coffee berry borer Hypothenemus hampei, the main coffee pest in the world. In this study, baseline determination and resistance monitoring to cyantraniliprole were carried out in Brazilian populations of H. hampei. Evaluations were carried out for three years with representative field-collected populations from nine coffee-producing states in Brazil, using artificial diet containing the insecticide. The likelihood of control failure due to cyantraniliprole resistance was also determined. Populations from Campo do Meio, Linhares and Jaú were more susceptible (<2-fold resistance) to cyantraniliprole than populations from Patrocínio and Londrina (17-fold). Nonetheless, the frequency of cyantraniliprole resistance insects was low and not significant throughout the regions survey and the likelihood of control failure was negligible. Therefore, cyantraniliprole remains an important management tool against the coffee berry borer without current problems of control failure. However, enough field variation in susceptibility to cyantraniliprole exists justifying attention and careful management of this insecticide to prevent quick development of insecticide resistance in populations of this insect pest species.

Exposure to cyantraniliprole causes mortality and disturbs behavioral and respiratory responses in the coffee berry borer (Hypothenemus hampei).

BACKGROUND: Hypothenemus hampei Ferrari (Coleoptera: Curculionidae) is the main pest of coffee due to the damage caused to coffee berries. Effective management methods and prevention of insecticide resistance are urgently needed against this insect. Bioassays were conducted to assess the effects of the diamide insecticide cyantraniliprole on H. hampei. Cyantraniliprole is the most recent compound registered against this species after the phasing out of endosulfan, the main insecticide historically used against the coffee borer for the past 30 years. Toxicity, survival, progeny production, respiration rate, and behavioral responses to cyantraniliprole were evaluated. RESULTS: Cyantraniliprole was toxic to adult H. hampei (LC50 = 0.67 mg mL-1 and LC90 = 1.71 mg mL-1 ). Adult survival was 95% without exposure to cyantraniliprole, decreasing to 52% in insects exposed to LC50 cyantraniliprole and 27% in insects treated with LC90 cyantraniliprole. Furthermore, H. hampei showed reduced mobility on insecticide-treated surfaces. The insecticide also led to a decrease in the respiration rate of H. hampei for up to 3 h after exposure, altering behavioral responses and locomotor activity. CONCLUSION: Cyantraniliprole exhibits lethal and sublethal effects on H. hampei and can be used in rotation in integrated pest management programs for control of this species in coffee cultivation systems. © 2019 Society of Chemical Industry.

Economic injury levels and economic thresholds for Leptoglossus zonatus (Dallas) (Hemiptera: Coreidae) infesting seed maize.

BACKGROUND: Although Leptoglossus zonatus is considered a secondary pest of maize grown for grain, when grown for seed, this pest can cause significant economic damage. There are no records of management recommendations for this pest. The objectives of this work were to quantify losses caused by L. zonatus to different genotypes used for seed maize production and to estimate the acute toxicity of selected insecticides to L. zonatus using different application technologies. The ultimate goal was to calculate economic injury levels (EILs) and develop economic thresholds (ETs) for L. zonatus infesting seed maize. RESULTS: EILs and ETs varied, respectively, from 3 to 8 and from 2 to 6 adults per 1000 plants, depending on the genotype, insecticide and application technology. Effective control was obtained by using aerial or ground application of λ-cyhalothrin (10.6%) + thiametoxan (14.1%) or permethrin (38.4%) at the rates of 1.48 mL ha-1 and 27.10 mL ha-1 , respectively, or ground application of methomyl (21.5%) at the rate of 244.06 mL ha-1 . CONCLUSION: Maize grown for seed is susceptible to L. zonatus damage during reproductive stages, and the pest densities requiring management vary with genotype, insecticide, and application technology. These results contribute significantly to integrated pest management (IPM) for seed maize. © 2017 Society of Chemical Industry.

Lethal and sublethal effects of seven insecticides on three beneficial insects in laboratory assays and field trials.

Lethal and sublethal effects of insecticides on target and non-target arthropods are a concern of pest management programs. Cycloneda sanguinea, Orius insidiosus and Chauliognathus flavipes are important biological control agents for aphids, whitefly, lepidopterus eggs, thrips and mites. All three test species were subjected to a toxicity study using the insecticides acephate, bifenthrin, chlorantraniliprole, chlorpyrifos, deltamethrin, imidacloprid, and thiamethoxam. Experiments were done in the lab and field. In the laboratory we evaluated the mortality and sublethal effects of the concentration that killed 20% of the population (LC20) on feeding, repellence and reproduction of the species tested. The lethal effects of these insecticides at the recommended doses was evaluated in the field. Concentration-response bioassays indicated chlorantraniliprole had the lowest toxicity, while chlorpyrifos and acephate were the most toxic. Test species exposed to filter paper surfaces treated with pyrethroids, neonicotinoids and organophosphates were repelled. On the other hand, test species were not repelled from surfaces treated with chlorantraniliprole. Chlorantraniliprole therefore seemed to be the least dangerous insecticide for these three beneficial arthropod test species.

Trichomes and hydrocarbons associated with the tomato plant antixenosis to the leafminer.

The objective of this work was to study the density of trichomes and hydrocarbons associated with the resistance by antixenosis of 42 subsamples of tomato plants from the Horticultural Germplasm Bank of the Universidade Federal de Viçosa (HGB-UFV) to Liriomyza trifolii. These subsamples were studied in addition to 'Santa Clara' cultivar, which was used as a standard of susceptibility to leafminers. The evaluated characteristics were the number of mined leaflets per plant, mines per plant, trichome density and chemical compounds in the leaves. Differences were detected among the subsamples in the variables studied. We identified 20 peaks in the chromatograms of leaf hexane extract the subsamples tested. The subsamples HGBs - 216, 813, 985, 987, 991, 992, 993, 1532, 1989, 1991, 2048, 2055, 2064, 2068, 2073, 2075, 2089, 2096 and 2097 were selected as sources of resistance to L. trifolii. The resistance mechanism associated to these subsamples was antixenosis. In addition, the low density of trichomes and the chemical compounds in the subsamples can be possible causes of pest resistance.

[Effects of irrigation, environmental variability and predatory wasp on Leucoptera coffeella (Guérin-Méneville) (Lepidoptera: Lyonetiidae), in coffee plants]. / Efeitos de variáveis ambientais, irrigação e vespas predadoras sobre Leucoptera coffeella (Guérin-Méneville) (Lepidoptera: Lyonetiidae) no cafeeiro.

The population density of the coffee leaf miner Leucoptera coffeella (Guérin-Méneville) can be affected by environmental variables in irrigated agroecosystems and the occurrence of predatory wasps such as Vespidae. In here, we aimed to evaluate the effects of environmental variables, drip irrigation depths and predation by wasps on the population density of L. coffeella. The experiment was carried out during 2004 and 2005 in a Coffea arabica plantation cultivated in the county of Jaboticatubas, Minas Gerais State, Brazil. The different irrigation depths set through drip were established considering the daily depth required by the IRRIPLUS program, which was equal to 100%, and two other lower (51% and 72%) and higher (124% and 145%) values, having the control without irrigation. In order to evaluate the coffee leaf miner population density and predation, the number of active and preyed mines was determined on the fourth pair of leaves in a group of ten plants. For the study of interactions among the environmental variables, irrigation depths with the mine density of L. coffeella and predatory wasps, the following methods were used: multivariated analysis, simple linear regression and trail. We concluded that higher pluvial precipitation, solar radiation and irrigation depths would reduce population density of the coffee leaf miner. Furthermore, the increase in density of the predatory wasps was dependent on the population level of L. coffeella.

Efeitos de variáveis ambientais, irrigação e vespas predadoras sobre Leucoptera coffeella (Guérin-Méneville) (Lepidoptera: Lyonetiidae) no cafeeiro / Effects of irrigation, environmental variability and predatory wasp on Leucoptera coffeella (Guérin-Méneville) (Lepidoptera: Lyonetiidae), in coffee plants

A densidade populacional do bicho-mineiro do cafeeiro Leucoptera coffeella (Guérin-Méneville) pode ser afetada por variáveis ambientais em agroecossistemas irrigados e vespas predadoras tais como Vespidae. Assim, objetivou-se neste trabalho avaliar os efeitos das variáveis ambientais, de lâminas de irrigação via gotejamento, e da predação por vespas na densidade populacional de L. coffeella. O experimento foi conduzido entre os anos de 2004 e 2005, em lavoura de Coffea arabica L. no município de Jaboticatubas, MG, Brasil. As diferentes lâminas de irrigação, aplicadas via gotejamento, foram estabelecidas tomando por referência a lâmina diária requerida pelo programa IRRIPLUS, que foi igual a 100 por cento e, duas outras abaixo, 51 por cento e 72 por cento, e acima, 124 por cento e 145 por cento, com a testemunha sem irrigação. Para a avaliação da densidade populacional do bicho mineiro e da predação determinou-se o número de minas ativas e predadas no quarto par de folhas do ramo mediano em dez plantas. Para estudar as interações entre as variáveis ambientais, lâminas de irrigação com as densidades de minas de L. coffeella e vespas predadoras foram realizadas análise multivariada, análises de regressão linear simples e trilha. Conclui-se que a maior precipitação pluvial, radiação solar e lâminas de irrigação reduzem a densidade populacional do bicho-mineiro. Além disso, o aumento na densidade das vespas predadoras foi dependente dos níveis populacionais de L. coffeella.

The population density of the coffee leaf miner Leucoptera coffeella (Guérin-Méneville) can be affected by environmental variables in irrigated agroecosystems and the occurrence of predatory wasps such as Vespidae. In here, we aimed to evaluate the effects of environmental variables, drip irrigation depths and predation by wasps on the population density of L. coffeella. The experiment was carried out during 2004 and 2005 in a Coffea arabica plantation cultivated in the county of Jaboticatubas, Minas Gerais State, Brazil. The different irrigation depths set through drip were established considering the daily depth required by the IRRIPLUS program, which was equal to 100 percent, and two other lower (51 percent and 72 percent) and higher (124 percent and 145 percent) values, having the control without irrigation. In order to evaluate the coffee leaf miner population density and predation, the number of active and preyed mines was determined on the fourth pair of leaves in a group of ten plants. For the study of interactions among the environmental variables, irrigation depths with the mine density of L. coffeella and predatory wasps, the following methods were used: multivariated analysis, simple linear regression and trail. We concluded that higher pluvial precipitation, solar radiation and irrigation depths would reduce population density of the coffee leaf miner. Furthermore, the increase in density of the predatory wasps was dependent on the population level of L. coffeella.

Sampling plan for Thrips (Thysanoptera: Thripidae) on cucumber.

This work determines the best technique, sampling unit and the number of samples to compose a sampling plan for Frankliniella schultzei (Trybom) and Thrips palmi (Karny) (Thysanoptera: Thripidae) on cucumber. The efficacy of three sampling techniques: leaf beating on a plastic tray, direct counting of insects on the lower leaf surface, and whole leaf collection in bags were compared in nine commercial cucumber crops using three sampling units (a leaf from a branch located in the apical, median or basal third of the canopy). The number of samples was determined based on the relative variance and the economic precision for the best technique and sampling unit. The direct counting of insects on the apical third of the plant canopy was the best sampling technique for F. schultzei based on one leaf surveyed per plant using 38 plants per field. The best sampling technique for T. palmi was the leaf beating on a tray using one leaf of the apical third per plant and 35 plants per field. When joining both species, the best sampling system was the direct counting on the apical third, and it requires sampling one leaf per plant using at least 35 plants per field. These results facilitate the decision-making for the management of thrips on cucumber and aggregate the benefits of the correct decision for the adoption of strategies for population reduction.

Sampling plan for Thrips (Thysanoptera: Thripidae) on cucumber / Plano de amostragem para Tripes (Thysanoptera: Thripidae) em pepino

Este trabalho determina a melhor técnica, unidade amostral e o número de amostras para compor um plano de amostragem para os tripes Frankliniella schultzei (Trybom) e Thrips palmi (Karny) em pepino. A eficácia de três técnicas de amostragem: batida de folhas em bandeja plástica branca, contagem direta de insetos na face inferior das folhas e coleta de folhas em sacola plástica foi comparada em nove cultivos comerciais de pepino, empregando três unidades amostrais (uma folha de ramo localizado nos terços apical, mediano e basal do dossel da planta). Baseado na variância relativa e precisão econômica dos melhores sistemas amostrais (melhores técnicas e unidades amostrais), calculou-se o número de amostras para a composição do plano de amostragem convencional. O sistema mais adequado para a amostragem de F. schultzei em pepino foi a contagem direta de insetos em folha do terço apical do espaldeiramento. Para tanto, deve-se amostrar uma folha por planta em 38 plantas/lavoura. Para a amostragem de T. palmi, o melhor sistema foi a batida de folha do terço apical do espaldeiramento em bandeja plástica. Na amostragem conjunta das duas espécies, o sistema mais adequado foi a contagem direta dos insetos em folha do terço apical do espaldeiramento. Nesse caso, amostra-se uma folha por planta, em 35 plantas/lavoura. Estes resultados facilitam a tomada de decisão no manejo de tripes em pepino, agregando os benefícios da decisão correta para adoção ou não de práticas de redução populacional.

This work determines the best technique, sampling unit and the number of samples to compose a sampling plan for Frankliniella schultzei (Trybom) and Thrips palmi (Karny) (Thysanoptera: Thripidae) on cucumber. The efficacy of three sampling techniques: leaf beating on a plastic tray, direct counting of insects on the lower leaf surface, and whole leaf collection in bags were compared in nine commercial cucumber crops using three sampling units (a leaf from a branch located in the apical, median or basal third of the canopy). The number of samples was determined based on the relative variance and the economic precision for the best technique and sampling unit. The direct counting of insects on the apical third of the plant canopy was the best sampling technique for F. schultzei based on one leaf surveyed per plant using 38 plants per field. The best sampling technique for T. palmi was the leaf beating on a tray using one leaf of the apical third per plant and 35 plants per field. When joining both species, the best sampling system was the direct counting on the apical third, and it requires sampling one leaf per plant using at least 35 plants per field. These results facilitate the decision-making for the management of thrips on cucumber and aggregate the benefits of the correct decision for the adoption of strategies for population reduction.