RESUMO Este trabalho teve por objetivo verificar o efeito do manejo da irrigação e da população de plantas
Euschistus heros (Fabricius, 1798) and Dichelops furcatus (Fabricius, 1775) are key pests of agricultural crops in Brazil. Chemical insecticides are the main control tactic used against these species. Here, we investigated the susceptibility of E. heros and D. furcatus from distinct regions to the mains insecticides used to stink bugs control in Brazil. Field populations of these species were collected throughout the 2017–2019 crop seasons and insects were exposed to insecticides in dip-test bioassays using fresh green bean pods. Populations of E. heros exhibited low variation in the susceptibility to acephate (LC50 = 172.2 to 1,008 µg a.i. per ml), and thiamethoxam (LC50 = 28.8 to 433.9 µg a.i. per ml); resistance ratios were less than 5.9- and 15.1-fold, respectively. In contrast, these populations had higher variation in the susceptibility to bifenthrin (LC50 = 26.7 to 636.1 µg a.i. per ml) and lambda-cyhalothrin (LC50 = 10.0 to 636.1 µg a.i. per ml); resistance ratios reaching 23.8- and 63.6-fold, respectively. Susceptibility monitoring data indicated a higher susceptibility of E. heros to the manufacturers field-recommended rates of acephate, lambda-cyhalothrin + thiamethoxam, and bifenthrin + acetamiprid than lambda-cyhalothrin. Populations of D. furcatus exhibited low variation in the susceptibility to acephate (LC50 = 219.2 to 614.1 µg a.i. per ml), bifenthrin (LC50 = 62.8 to 197.4 µg a.i. per ml), and lambda-cyhalothrin (LC50 = 189.5 to 2,538 µg a.i. per ml); resistance ratios were less than 13.4-fold. In summary, populations of E. heros are less susceptible to pyrethroids, while populations of D. furcatus have similar susceptibility to the insecticides evaluated.
Normalmente, a aplicação de inseticidas para o controle de Anticarsia gemmatalis na cultura da soja é realizada com bicos hidráulicos. Dentre outras possibilidades se destacam a assistência de ar junto à barra de pulverização e a aplicação de baixo volume oleoso por atomizadores rotativos de discos. Em um experimento realizado na cultura da soja, na safra 2009/10, avaliou-se a eficiência de controle de A. gemmatalis utilizando-se sistemas de aplicação e inseticidas. O delineamento utilizado foi bifatorial com o fator A constituído por sistemas de aplicação, sendo: A1 - pulverização com atomizadores rotativos de discos; A2 - pulverização com bicos hidráulicos; A3 - pulverização com assistência de ar e o fator D, constituído por inseticidas, sendo: D1 - Cipermetrina e D2 - Lufenurom + profenofós. Não houve interação do inseticida com o sistema de aplicação; além disso, a mistura de inseticidas Lufenurom + Profenofós apresentou efeito residual superior a Cipermetrina. O sistema de aplicação baixo volume oleoso com atomizadores rotativos de discos e o sistema de bicos hidráulicos com assistência de ar junto à barra de pulverização são mais eficientes que a pulverização com bicos hidráulicos no controle de Anticarsia gemmatalis na cultura da soja.
It is important to quantify the population of stink bugs in the soybean, in order to determine the actions which are necessary for their control to protect the crop from losses in production, together with a reduction in cost and less environmental impact. The objectives of this study were to determine the sample size (the number of sampling points) needed to estimate the average population density of the bugs, and to verify the variability in sample size for the phases and species of the bugs and the phenological stages of the plants. In an area of 6.16 ha of soybeans, a grid of 154 sampling points, spaced 20 × 20 m apart, was laid out. Population-density data were collected for nymphs and adults of the species Dichelops furcatus (Fabricius, 1775), Piezodorus guildinii (Westwood, 1873), Edessa meditabunda (Fabricius, 1794), Nezara viridula (Linnaeus, 1758), Euschistus heros (Fabricius, 1794) and Chinavia sp. (Say, 1832) employing a vertical beat sheet at 14 different phenological stages. Measurements of central tendency and variability, the Morisita index and the k parameter of negative binomial distribution were all calculated. Homogeneity of variances was verified and the sample size calculated. There is variability in the sample size when estimating the average population density of bugs across the phases and species of bug and the phenological stages of the soybean. Smaller sample sizes are necessary for the nymphs of P. guildinii and the final phenological stages (R6, R7.1, R7.3 and R8.2). Thirty-six sampling sites are enough to estimate the average population density of bugs in the final phenological stages (R6, R7.1, R7 .3 and R8.2) at an error of estimation equal to 30% of the estimated mean and at a level of confidence of 95%.
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