Controle de adultos de Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) em milho com uso de iscas tóxicas

Abstract

The Brazilian economy is supported by agribusiness. However, the continuous cycle of food, biofuel and fiber production and the favorable climate contribute to the incidence of insect pests throughout the year, which can affect productivity indicators. The species fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) is considered the main pest of the corn crop, due to the voracity of the caterpillars and the occurrence throughout the crop cycle. Chemical control and the use of plants with Bt technology have been constantly used, resulting in the emergence of insect populations resistant to the different insecticides and Bt proteins expressed, leading to negative implications for the implementation of Integrated Pest Management Programs (IPM). Bt plants are developed through biotechnology to be able to resist certain insect-pests. To make them resistant, a gene expressing a protein that is toxic to certain insects such as caterpillars, beetles, flies, etc. has been inserted into their DNA. An alternative to reduce the population of FAW is using toxic baits, which are attractants contaminated with substances that negatively affect the insects. The objectives of this study were to evaluate the effects of food attractants to FAW adults associated with different insecticides under controlled laboratory conditions and the reduction of field damage in genetically modified corn (Bt and non-Bt) by spraying toxic bait. To this end, under controlled conditions (bioassays), seven food attractants were tested in a chance-choice study and four attractants in a no-choice study. For the death rate study, the food attractant was associated with six chemical insecticides. The experimental design used in the bioassays was entirely randomized design. The number of insects that fed on the food attractants, the time (in minutes) they remained in the food attractant and the death rate of FAW adults were the parameters evaluated. The food attractants sugarcane syrup (10%) and Noctovi® 43sb were significantly more efficient regarding feeding time, while the highest number of landings was observed in the Noctovi® 43sb treatment, both for females and total adults. The insecticides Methomyl, Lambdacyhalothrin and Spinosad associated with food attractant, are promising toxic baits for FAW management. The field experiments were conducted in three cities located in the south of the state of Mato Grosso do Sul, Brazil, during the 2018 and 2019 crop year, in commercial corn fields, with and without Bt technology, in eight locations and six treatments, four of them with toxic bait application. The experimental design was with randomized blocks, and the food attractant associated with the insecticide molecule was applied to the crop at the crop at stages V1 and V3. The adult population was monitored with sex pheromones and the percentage of damage quantified using the Davis scale scores. The application of the toxic bait, in strips equal or less than 50 meters apart, significantly reduced the percentage of damage and injury to plants. The greatest effect on these parameters was when associated with Bt corn crops. The "attract and kill" technique under the conditions studied can be adopted as another tool for the control of FAW adults, within programs of Integrated Pest Management in the culture of second crop corn.