The effects of foliar spray application of silicon on plant damage levels and components of larval biology of the pest butterfly<i>Chlosyne lacinia saundersii</i>(Nymphalidae)

Abstract

Abstract We investigated sunflower leaf palatability to Chlosyne lacinia saundersii Doubleday & Hewitson (Lepidoptera: Nymphalidae) in plants treated with silicon (Si) and subjected to mechanical injury. We also examined the effects of those treatments on plant development. The experimental study was carried out as a completely randomized design, consisting of the six treatments (10 replicates each): (1) control, (2) plants mechanically injured, (3) Si applied around the plant stem (Si drench), (4) Si drench + injured, (5) Si drench + foliar spray, and (6) Si drench + foliar spray + injured. Si drench + injured significantly reduced the percentage of caterpillar-injured leaves (CIL), leaf area consumed (LAC), and caterpillar weight (CW), leading to increased caterpillar mortality. The only intrinsic plant characteristic affected by the treatments was Si content (SiC), which was higher in plants treated with either Si drench + foliar spray or Si drench + foliar spray + injured. Negative correlations were observed between SiC and the variables CIL, LAC and CW, whereas positive correlations were observed between CIL and LAC, CIL and CW, and LAC and CW. The treatment strategy of Si combined with artificial mechanical injury affects leaf palatability and development of C. lacinia saundersii, conferring resistance to sunflower plants as a function of Si accumulation, although it did not increase crop vegetative variables. Keywords: insectainduced resistanceIPMsilicic acid Acknowledgments The authors thank the National Council for Scientific and Technological Development (Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq) and the Coordination of Improvement of Higher Education Personnel (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – CAPES) for fellowships, as well as the Minas Gerais State Research Foundation (Fundação de Amparo à Pesquisa de Minas Gerais – FAPEMIG) for financial support. Notes aMeans followed by the same letter in a column are not significantly different, as defined using Tukey's test (P ≤ 0.05). aMeter reading (SPAD-502). *Not significant according to F-test (P > 0.05). *Significant (P ≤ 0.05) according to t test.