Antifeedant effect of commercial chemicals and plant extracts againstSchistocerca americana(Orthoptera: Acrididae) andDiaprepes abbreviatus(Coleoptera: Curculionidae)

Abstract

The deterrent effect of seven commercial compounds against Schistocerca americana (Drury) nymphs and Diaprepes abbreviatus L. adults, two important citrus pests, was investigated. Extracts of three Florida local plants were also tested as deterrents. Antifeedant activity was assayed using a leaf-disk bioassay in choice and no-choice tests. The residual activity of the commercial compounds that significantly deterred the insects was assayed by applying them to foliage of citrus plants exposed to three time intervals of sunlight. Sabadilla, azadirachtin and ryanodine effectively deterred S. americana, whereas rotenone, sabadilla and ryanodine reduced the feeding activity of D. abbreviatus. Methanol and methylene chloride extracts of Ceratiola ericoides Michaux deterred D. abbreviatus, but only methylene chloride extract dissuaded S. americana. Methanol extract of Ardisia crenata Sims functioned as a feeding deterrent against both S. americana and D. abbreviatus, but only the latter species was deterred by methylene chloride extract of A. crenata. Extracts of Illicium parviflorum Michaux ex Ventetat only dissuaded the insects in choice bioassays. Rapid loss of effectiveness was observed under field conditions. Sabadilla was the only compound that maintained its antifeedant properties in the field, but only against S. americana. Based on their deterrency, some of the commercial products and plant extracts have potential for use as substitute crop protectants against the pest species tested.