Induction of Caterpillar Resistance in Sunflower Using Silicon and Acibenzolar-S-Methyl

The sunflower caterpillar Chlosyne lacinia saundersii (Lepidoptera: Nymphalidae) is considered a major pest in sunflower, causing severe defoliation and, thus, threatening production of oilseed. Chemical control remains the most widely used method for the management of this defoliator. To manage insect pests, there is a need to use substances of low toxicity that are able to stimulate the plant to use its own defense mechanisms. Therefore, in this study, we evaluated the induction of resistance by silicon (Si) and acibenzolar-S-methyl (ASM) against C. lacinia saundersii in sunflower plants. The bioassay was conducted in a completely randomized design using 4 treatments and 10 replicates. The treatments were: (1) Si; (2) ASM; (3) Si+ASM, and (4) the control. The biological parameters of the caterpillar and the accumulation of Si and lignin in plants were evaluated. The application of resistance inducers reduced weight of the caterpillars 10 and 15 days of age. The use of Si alone or Si+ASM promoted the accumulation of this element; however, only ASM increased lignin content in plants. Negative correlations between the silicon content and larval weight and between the silicon content and lignin content were observed. Therefore, the application of silicic acid or ASM can inhibit the development of C. lacinia saundersii, conferring a resistance in plants attributable to the accumulation of silicon and lignin, thus serving as an alternative approach that may potentially be integrated into the management of this key pest in sunflower crops.