Modos de exposição de inseticidas, estratégias químicas e tecnologia de aplicação para o manejo de percevejos fitófagos nas culturas do milho e da soja

Abstract

Phytophagous pentatomid stink bugs are among the main pests that attack soybean and corn crops in the State of Mato Grosso do Sul, causing losses and being difficult to control. This research had three different objectives as follows: evaluate the action of insecticides in different exposure modes for adults of Dichelops melacanthus (Dallas, 1851); evaluate chemical strategies applied in seed treatment and spraying in the plant and apply technique and on plants aiming at the control of corn stink bugs; and to evaluate the effect of different spray nozzles and volumes for the control of Euschistus heros (Fabricius, 1798) on soybean. In the insecticide exposure mode essay, adults of the bug D. melacanthus were exposed exclusively to the direct contact, tarsal contact and ingestion, in 15 different chemical treatments, and a control (untreated). In the test involving application technology, the control of E. heros was evaluated using the flat fan nozzles-XR plano and empty cone and the spray volumes of 100, 150 and 200 L ha-1 in the two spray nozzles, applying the insecticide (in g a.i. ha-1 ) sulfoxaflor + lambda-cyhalothrin (30 + 45) in the soybean, as well as a non-sprayed control. In the trial with different chemical strategies for the control of stink bugs in corn, the insecticide (in g a.i. ha-1 ) imidacloprid + thiodicarb (25.0 + 75.0) was used in seed treatment, while the mixture of insecticides (in g a.i. ha-1 ) imidacloprid + beta-cyfluthrin (100.0 + 12.5) was sprayed using the plant and apply technique and at 3 and 10 days after the emergence (DAE) of corn. These treatments were evaluated separately or in combination, in addition to a control treatment. The results showed that the most effective mode of exposure for the control of D. melacanthus adults is through direct contact of the insect with the insecticide sprayed, followed by tarsal contact and lastly in the ingestion mode, considered the most ineffective. In the test on application technology, the types of spray tips showed similar results for the control of E. heros, while the highest spray volume tested was more promising for the control of this pest. In the experiment with different strategies for the chemical control of stinkbugs in maize, seed treatment in association with spraying in the early stages of corn development proved to be the most effective tactics for the initial protection of plants from attack by stinkbugs. The exclusive spraying of the insecticide in plant and apply was, in general, ineffective for protecting corn from attack by stink bugs.