RESUMO
The corn leafhopper Dalbulus maidis (Hemiptera: Cicadellidae), is an important corn pest in most of tropical and subtropical America. This leafhopper has a rich natural enemy complex of which parasitoids and pathogens are the most studied; knowledge on its predators is limited. We noted the presence of the native assassin bug Zelus obscuridorsis (Hemiptera: Reduviidae) predating diverse motile insects, including the corn leafhopper, on corn plants cultivated in household vegetable gardens in San Miguel de Tucumán (Argentina); in order to verify its predatory actions, we exposed lab-bred individuals of D. maidis to adults of Z. obscuridorsis. The predators were starved for 24 h before trials in which the corn leafhopper in different developmental stages were exposed. Zelus obscuridorsis is highly skilled in catching specimens in motion, but it was not able to prey on eggs. The predator was capable to catch and prey on nymphs and adults.
RESUMO
The objective of this study was to evaluate the reaction of corn genotypes to eyespot caused by Kabatiella zeae under natural field conditions. The assay was carried out during the 2006/2007 growing season, in Pato Branco-Paraná State, consisting of 33 hybrids and two sowing seasons, on 10/13 and 12/27/2006, respectively; and in the 2007/2008 growing season, in the same place, with 10 hybrids and two sowing seasons, on 10/20 and 11/12/2007, respectively, and in Palma Sola-Santa Catarina State, with 8 hybrids and one sowing season, on 09/30/2007. Disease intensity was determined by means of severity evaluations. The observed corn plant reactions allowed genotypes with different levels of eyespot resistance to be discriminated. Hybrids AG 9020 and SPRINT were the most susceptible to the disease, while AS 1565 and DKB 234 were the most resistant; this behavior was repeated in both years and growing seasons. It was concluded that the variation in susceptibility to eyespot among the hybrids tested, may have been influenced by ambient conditions.
O objetivo deste trabalho foi avaliar a reação de genótipos de milho quanto à mancha ocular causada por Kabatiella zeae sob condições naturais de infecção. Os ensaios foram instalados na safra 2006/2007, no município de Pato Branco, PR, com 33 híbridos e com duas épocas de semeadura, dia 13/10 e 27/12/2006, respectivamente; e na safra 2007/2008, no mesmo município, com 10 híbridos e com duas épocas de semeadura, dia 20/10 e 12/11/2007, respectivamente e no município de Palma Sola, SC, com oito híbridos e com uma época de semeadura, dia 30/09/2007. A intensidade da doença foi determinada pela avaliação de severidade em todos os híbridos de milho, em diferentes estádios de desenvolvimento. As reações de milho observadas permitem separar estatisticamente genótipos com diferentes níveis de resistência à mancha ocular. Os híbridos AG 9020 e SPRINT apresentaram maior suscetibilidade à doença, e AS 1565 e DKB 234, maior resistência, repetindo este comportamento nos dois anos e épocas de cultivo. Concluiu-se que a variação na suscetibilidade à mancha ocular entre os híbridos de milho testados, pode ter sido influenciada pelas condições ambientais.
RESUMO
The objective of this study was to evaluate the reaction of corn genotypes to eyespot caused by Kabatiella zeae under natural field conditions. The assay was carried out during the 2006/2007 growing season, in Pato Branco-Paraná State, consisting of 33 hybrids and two sowing seasons, on 10/13 and 12/27/2006, respectively; and in the 2007/2008 growing season, in the same place, with 10 hybrids and two sowing seasons, on 10/20 and 11/12/2007, respectively, and in Palma Sola-Santa Catarina State, with 8 hybrids and one sowing season, on 09/30/2007. Disease intensity was determined by means of severity evaluations. The observed corn plant reactions allowed genotypes with different levels of eyespot resistance to be discriminated. Hybrids AG 9020 and SPRINT were the most susceptible to the disease, while AS 1565 and DKB 234 were the most resistant; this behavior was repeated in both years and growing seasons. It was concluded that the variation in susceptibility to eyespot among the hybrids tested, may have been influenced by ambient conditions.
O objetivo deste trabalho foi avaliar a reação de genótipos de milho quanto à mancha ocular causada por Kabatiella zeae sob condições naturais de infecção. Os ensaios foram instalados na safra 2006/2007, no município de Pato Branco, PR, com 33 híbridos e com duas épocas de semeadura, dia 13/10 e 27/12/2006, respectivamente; e na safra 2007/2008, no mesmo município, com 10 híbridos e com duas épocas de semeadura, dia 20/10 e 12/11/2007, respectivamente e no município de Palma Sola, SC, com oito híbridos e com uma época de semeadura, dia 30/09/2007. A intensidade da doença foi determinada pela avaliação de severidade em todos os híbridos de milho, em diferentes estádios de desenvolvimento. As reações de milho observadas permitem separar estatisticamente genótipos com diferentes níveis de resistência à mancha ocular. Os híbridos AG 9020 e SPRINT apresentaram maior suscetibilidade à doença, e AS 1565 e DKB 234, maior resistência, repetindo este comportamento nos dois anos e épocas de cultivo. Concluiu-se que a variação na suscetibilidade à mancha ocular entre os híbridos de milho testados, pode ter sido influenciada pelas condições ambientais.