Indução de resistência em arroz a Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera Noctuidae) pela aplicação de silício

Abstract

The rice (Oryza sativa L.) is the basic food of nearly half the world's population. There are several pests that attack this culture, and the Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) is one of them. The control of this insect pest is done with successive applications of insecticides, however, are found several cases of resistance to pesticides, which justifies the search for other methods of control to be associated in the management of this insect. The aim of this study was to evaluate the effects of silicon application in rice induced resistance to S. frugiperda. The treatments were: T1-Control (without application of Si), silicon-T2 (drench) and T3-silicon (leaf). The Si was applied by a solution of silicic acid 1% at a dosage equivalent to 3 SiO2 t ha-1. It was adopted a completely randomized design with three replications and 10 treatments, each replicate consisting of five plots (50 plates / treatment) to evaluate biological aspects of S. frugiperda. Were evaluated the vegetative characteristics such as height, chlorophyll content, fresh and dry matter of aerial part and Si content. To assess mechanisms of non-preference of S. frugiperda was used a randomized block design with three prior treatments and 20 blocks in test-choice. Were released 12 caterpillars in 2nd instar on the center of Petri dishes and after 24, 42 and 72 h of infestation the caterpillars were counted for each treatment. After 72h was also evaluated the consumed leaf area. For the no-choice test was adopted a CRD with three treatments and 20 repetitions, with the release of 12 caterpillar on 2nd instar per dish and after 24h, 48h and 72h was evaluated survival percentage. There were no differences in the duration of larval and pupal, caterpillars survival, pupae viability and sex ratio. Insects fed on plants treated with Si showed lower consumption, reduction in larvae and pupae weight, decreased longevity of adult males and females and reduction in the number and viability of the 1st and 2nd oviposition when compared to control. The Si interferes negatively behavioral and biological the aspects of S. frugiperda, and also contributes with the development of the plants.