Renato Suekane

Damage level of the two-spotted spider mite Tetranychus urticae Koch (acari: tetranychidae) in soybeans

Among phytophagous spider mites, the two-spotted spider mite Tetranychus urticae Koch, 1836 is one of the most important agricultural pests, not only because of the damage it causes, but also because it has a wide host range, infesting many commercial crops such as leafy greens, cotton, beans, and soybeans, among others. This study was carried out in a greenhouse of the Faculdade de Ciencias Agrarias (FCA) of the Universidade Federal da Grande Dourados (UFGD), located in the city of Dourados, state of Mato Grosso do Sul. The experiment was arranged in a randomized block design with 5 treatments and 4 replicates. The treatments consisted of 5 levels in percentage of chlorotic symptoms (indicating mite damage): 0%, 25%, 50%, 75%, and 100%. All of the characteristics evaluated, except for number of pods per plant, the number of seeds per plant, the total weight (productivity), and the weight of 1000 seeds, were significantly influenced by the different levels of chlorotic symptoms. The economic damage level for the two-spotted spider mite Tetranychus urticae, according to the equation y = 66.63-0.51 x, based on the price of US

Ataque de lagartas em estilo-estigma e grãos da espiga de diferentes híbridos de milho-Bt

11.00 per bag of soybeans and a control cost of US

Spatial distribution of soybean plants infested with whitefly Bemisia tabaci (Gennadius, 1889) (Hemiptera: Aleyrodidae)

16.00, would be 15.80% chlorotic symptoms. At a price of US

Disposição espacial e injúrias da lagarta-do-cartucho Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) em milho

29.00 per bag with the same control cost, the economic damage level would be 13% of chlorotic symptoms.

Danos da Mosca-Branca Bemisia Tabaci (Genn.) e distribuição vertical das ninfas em cultivares de soja em casa de vegetação

A cultura do milho e atacada por diversas pragas ao longo do seu ciclo e recentemente foi constatada a ocorrencia de Helicoverpa armigera atacando espigas de milho no Brasil. O objetivo do trabalho foi avaliar o ataque de lagartas em estilo-estigma e graos da espiga de diferentes hibridos de milho-Bt. O estudo foi realizado no municipio de Dourados (MS). Avaliaram-se os insetos encontrados nos estilos-estigma presentes em cinco espigas de milho por parcela. Foram realizadas tres avaliacoes dos estilos-estigma e uma quarta avaliacao dos danos nas espigas do milho. Houve diferenca estatistica significativa entre o numero de lagartas de Spodoptera frugiperda encontradas no estilo-estigma dos hibridos estudados. Ocorreu um maior numero de lagartas no hibrido de milho nao-Bt, proximo de 0,5 lagartas/estilo-estigma, seguido do hibrido de milho Cry1Ab, Cry1A.105, Cry2Ab2 e por ultimo o menos infestado, com a proteina VIP3Aa20. O hibrido de milho que expressa a proteina VIP3Aa20 apresentou menor numero de lagartas no estilo-estigma.

SELETIVIDADE DE INSETICIDAS SOBRE O COMPLEXO DE PREDADORES DAS PRAGAS DO ALGODOEIRO

Arq. Inst. Biol., v.85, 1-6, e0642016, 2018 RESUMO: A determinação do arranjo espacial da praga torna-se o primeiro passo para o estabelecimento de um plano de amostragem, pois, conforme o tipo de distribuição espacial da praga específica estudada, será necessário utilizar diferentes métodos de amostragem, variando o número e o tamanho da amostra na área. O presente trabalho objetivou estudar a distribuição espacial das plantas infestadas por Bemisia tabaci em condições de campo, na cultura da soja, por meio da determinação dos índices de agregação e dos testes de qui-quadrado de aderência para os principais tipos de distribuições teóricas de frequência. Os resultados mostraram que a porcentagem média de infestação da mosca-branca (B. tabaci) foi aumentando a partir do estádio V1, atingindo a máxima infestação de 60,3% no estádio R1. A partir do estádio R2, a porcentagem de infestação variou entre 20% e 40%. Os modelos de distribuições teóricas estudados indicam que o modelo poisson é o que melhor define a distribuição da mosca-branca.

Selectivity of pesticides over predators of cotton plant pests.

Spatial arrangement and damage by the fall armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) on maize The knowledge about the population dispersion patterns of Spodoptera frugiperda (J. E. Smith), the most important maize pest in Brazil, is crucial for the development of efficient techniques for its monitoring and management. The spatial distribution was studied in five maize experimental fields, one hectare each, divided in 100 plots, where five or 10 plants were assessed per plot. The adjustment of observed frequencies to the expected ones was tested according to Poisson, Negative and Positive Binomial distributions. Spodoptera frugiperda occurred in high population levels in the sampling field, with significant correlation between the damage score 3 and the number of medium-sized larvae, as well as for the number of infested plants with at least one medium-sized larva. There was not significant correlation between the damage score 3 and the number of small larvae. The model that better fitted to oviposition distribution data was the Positive Binomial, whereas the spatial arrangement of larvae attacking the corn ear was random. Positive Binomial distribution was that which better represented the population spatial distribution of infested plants, and the distribution of medium-sizedlarvae had aggregated distribution.

Impacto de diferentes níveis de desfolha artificial nos estádios fenológicos do algodoeiro

The whitefly (Bemisia tabaci) causes damage in the soybean crop by sucking the plant sap, transmission of viruses and promoting sooty mold that affect the growing and the soybean production. The goal of this work was to evaluate the direct damage of the whitefly, and the vertical nymph distribution, on soybean cultivars under greenhouse conditions. The experimental design was randomized blocks with 10 cultivars in a 10 x 2 factorial scheme (infestation and without infestation) and 4 replications. Counts were made of the number of eggs and nymphs in the upper, middle and lower third of the plants. The productive indices were: number of pods per plant and grains per pod, weight of 100 grains, and weight of 2 plants. The data were submitted to variance analysis and F test (α < 0.05), and the means were compared by Tukey test at 5% probability, obtaining the least significant difference between treatments. The cultivars were not affected by the B. tabaci attack at the infestations levels registered. CD 219 RR was the cultivar most infested by the whitefly nymphs. For better efficiency and use of time in the evaluations, in greenhouse studies it is suggested that they be carried out in the upper and middle thirds of the soybean plants.