Alterações bioquímicas em milho submetido à herbivoria de spodoptera frugiperda (lepidoptera: noctuidae) sob tratamento com preparados homeopáticos e bacillus thuringiensis

Abstract

Maize (Zea mays L.) is an important agricultural crop; however, its productivity can be affected by insect pests, especially the fall armyworm (Spodoptera frugiperda J.E. Smith) (Lepidoptera: Noctuidae). The use of sustainable strategies, such as biological control with Bacillus thuringiensis (Bt) and homeopathic preparations, has been investigated as an alternative approach to stimulate natural plant defense mechanisms. This study aimed to evaluate biochemical changes in maize plants subjected to S. frugiperda herbivory under treatment with homeopathic preparations associated with B. thuringiensis. The experiment was carried out in a greenhouse and in the Entomology and Biochemistry Laboratory of the Federal University of Fronteira Sul, Erechim Campus, using Cunha maize variety. The treatments consisted of Chamomila 6CH + Bt, Nux vomica 6CH + Bt, and untreated control, evaluated at three periods: before treatment application, after treatment, and after caterpillar exposure. Soluble protein content and phenylalanine ammonia-lyase (PAL) activity were evaluated, as this enzyme is involved in the phenylpropanoid pathway and plant defense responses. The results showed that treatments affected plant biochemical responses, with emphasis on Chamomila 6CH + Bt, which promoted increases in protein concentration and higher PAL activity after treatment application. After S. frugiperda herbivory, treated plants maintained a tendency toward greater metabolic activation compared to the control, although with reduced statistical differences. It was concluded that the association between homeopathic preparations and B. thuringiensis may stimulate biochemical responses related to induced resistance in maize plants, representing a potential complementary tool for sustainable management of fall armyworm.