Effects of silicon application on the biochemistry of passion fruit and performance of Dione juno juno (Lepidoptera: Nymphalidae)

Abstract

Silicon (Si) is agronomically beneficial due to positive effects it provides to plant development, including the increased defensive response capacity against attack of herbivorous insects. This study evaluated the effects of applications of Si sources via soil and foliar sprays on yellow passion fruit biochemistry and Si-induced resistance to feeding preference and development of the major passion fruit pest, Dione juno juno. Two independent experiments were conducted with applications of calcium silicate (78–88% SiO2) via soil and as foliar sprays with the commercial product AgriSil® (98% SiO2) to plants of Passiflora edulis f. flavicarpa in a greenhouse. Four doses were tested for each Si source plus a control treatment. Biochemical analyses in the plants included the concentrations of Si and total phenolics, and activities of the enzymes peroxidase (POX), phenylalanine ammonia lyase (PAL), and polyphenol oxidase (PPO). Si-induced resistance to D. juno juno was investigated in feeding assays in the laboratory and on the insect’s development on potted-plants in the greenhouse. As main results, calcium silicate favoured the increase in Si content and the activities of POX and PAL, in addition to negatively affecting larvae feeding preference, leaf area consumed, and adult-stage parameters of D. juno juno. Agrisil led to increased Si content, total phenolics concentration, and POX activity, but did not affect the feeding preference, performance, and development of D. juno juno. Calcium silicate is promising for use in integrated pest management and could provide benefits to passion fruit production by reducing the economic losses by D. juno juno attack.