ÁCIDO SALICÍLICO COMO INDUTOR DE RESISTÊNCIA AO Tetranychus urticae (Koch) E Helicoverpa armigera EM CULTIVARES DE MORANGUEIRO

Abstract

This work aimed to evaluate the effect of salicylic acid on induction of resistance to spider mite (Tetranychus urticae (Koch) and Helicoverpa armigera. The density of trichomes and fluorescence were evaluated in strawberry cultivars. The evaluated cultivars were Aromas and Sweet Charlie. Five doses of salicylic acid (AS) (0, 25, 50, 75, 100 mg L-1) were used. To verify the effects of antixenosis and antibiosis, mites were submitted to the with and without choice test, where survival and oviposition were evaluated. The density and type of leaf trichomes were analyzed in the abaxial and adaxial faces of the leaflets of the strawberry cultivars. The effect of AS on the biology of H. armigera was evaluated. In addition, the fluorescence of the plants under the treatments and their relation with the level of stress was measured. In the without choice test, the survival mites rates were reduced of the intermediate doses of salicylic acid 25, 50 and 75mg L-1 in both cultivars. For the number of eggs deposited on leaflet, there was a significant dose effect, with a quadratic adjustment of the equation, where the Sweet Charlie cultivar was more effective than Aromas in reducing oviposition and mite survival on leaflets treated with resistance inducer. For the biology of H. armigera, a reduction in the life cycle in weight and length was observed at doses 25 and 50 mgL-1. In the fluorescence test monitoring the photosynthetic capacity, stress and injury effects were detected, where the 100 mgL-1 dose provided higher stress in the plants compared to the others. The AS doses interfered in plant morphology by altering the density of glandular trichomes and tectors in the leaflets, showing a positive effect on the increase of these structures when intermediate doses were applied. Concentrations of 25, 50 and 75 mg L-1 AS were the most efficient for the evaluated characteristics allowed to infer its potential as inducer of resistance in arthropod-pest in strawberry.