Ozone toxicity to Sitophilus zeamais (Coleoptera: Curculionidae) populations under selection pressure from ozone

Abstract

Two populations of Sitophilus zeamais (Coleoptera: Curculionidae) were subjected to selection pressure with ozone (O3), and the possibility of acquiring resistance to O3 was investigated. The pattern of locomotion and the rate of respiration were evaluated following each selection cycle. Two source populations were used in the study: one was a mixture composed of 30 populations (MP), and the other was composed of the population that was the least susceptible to O3 among these 30 populations (LSP). The beetles from each source population experienced selection cycles with O3 using the lethal time for 80% (LT80) of the insect population from each generation. The O3 toxicity (50 ppm at a continuous flow rate of 2 L min−1) to each generation was calculated using time-response bioassays. The locomotor pattern (distance traveled, resting period, and walking speed) and the respiratory rate (CO2 production) were also evaluated. The S. zeamais populations that were subjected to successive cycles of selection with O3 did not acquire resistance to O3, and the pattern of locomotion and the rate of respiration did not change following the selection cycles with O3.