Noctuids are the main phytophagous pests of gramineae and decisions about its control are based on percentage of defoliation, not considering the level of larval infestation. The objective of this study was to test the sweeping net in the evaluation Noctuidae population and of the principal groups of natural enemies in ryegrass (Lolium multiflorum Lam.), in the morning and at night. The work was conducted in two crops in Salvador do Sul, RS, Brazil. In the first experiment, insects were sampled weekly, and in the second one, which was complementary, the collections were done in each phase of ryegrass development, maintaining laboratorial rearing. From the first one, a total of 2,044 caterpillars were collected, but only 151 in the morning. Statistical differences occurred at night between sampling dates and caterpillar sizes. Three hundred and eighty seven spiders, 577 microhymenopterans and 983 other insects with interest in biological control were also captured; statistical significance was observed between day periods and dates for Carabidae, Forficulidae, Tachinidae, Nabidae, Vespidae, microhymenopterans and Araneae. From the second experiment eleven species were obtained, and Pseudaletia sequax Franc., 1951, was the predominant. The use of sweeping net allows the evaluation of Noctuidae population, as well as the main groups of natural enemies in ryegrass, in the evening.
Lolium multiflorum; Noctuidae; insect population; integrated pest management
