Effect of silicon on the morphology of the midgut and mandible of tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae) larvae

Abstract

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is an important insect pest causing serious losses to tomato plantations in Brazil. Some populations of T. absolute are reported to present insecticide resistance resulting in its control failure and the use of alternative control based on silicon, which is clean and sustainable, can reduce pesticide use, increasing fruit quality and protecting the environment. This study evaluated changes in the morphology of the midgut and the mandibles of T. absoluta larvae caused by feeding with compounds containing silicon. Larvae of T. absoluta were fed on tomato leaves with different compounds containing silicon and the histology of the midgut of fourth instar larvae was analyzed. The mandibles of all larval stages were dissected and analysed by scanning electron microscopy. There were no changes in the morphology of the mandibles of the larvae of T. absoluta fed on silicon compared to the control group. Larvae of T. absoluta from the control group and the treatments where the calcium silicate was applied to the soil had not differences in the morphology of the midgut epithelial cells, which had four cell types: digestive, goblet, regenerative and mycetocyte cells. In larvae of T. absoluta obtained from silicon-based treatments applied to the leaves, the midgut epithelium showed detachment of the basal membrane, which can characterize the possible effect of this toxic element to larvae of T. absoluta.