Toxic Activity of N-Oxide Derivatives against Three Mexican Populations of Spodoptera frugiperda.

Fall armyworm, Spodoptera frugiperda (J.E. Smith) is a polyphagous insect with natural resistance to insecticide; various strategies have been used for its control. Novel compounds derived from N-oxide have low toxicity to humans but are biologically activity against bacteria, fungi, parasites, and even insects. Five Noxide derivatives (QX1, QX2, QX3, QX4, and QX5) were evaluated through diet and spray assays to determine toxic activity and most-effective administration route in three Mexican populations of S. frugiperda. Larvae were collected from fields of maize, Zea mays L., in three regions of Mexico: Mante, Tamaulipas (Northeast); Durango, Durango (Northwest); and Tapachula, Chiapas (Southern). The three Mexican populations were sensitive to QX5 (benzofuroxan N-oxide derivative) that when ingested killed 100% of larvae, and had variable sensitivity to quinoxaline 1,4- di-N-oxide derivatives that negatively affected growth of larvae. Ingested QX2, QX3, and QX4 most inhibited growth (54-64%) of the Mante population. QX3 most inhibited growth (almost 90%) of the Tapachula population, and QX1 inhibited growth of 91% of the larvae in the Durango population. With topical application, all compounds killed less than 10% of the larvae, and only QX2 and QX3 inhibited growth of 31% of fall armyworm larvae from the Durango population. Benzofuroxane killed most and quinoxalines caused variation in growth inhibition of fall armyworm larvae; in both cases, ingestion was most effective in killing larvae. The benzofuroxan N-oxide derivative might have good potential for development of safer and more effective insecticides against this pest. [ABSTRACT FROM AUTHOR]