Innovative Enhancement of Zinc Oxide Nanoparticles (ZnO-NPs) Toxicity for Effective Weevils Control

Abstract

The research elucidates the innovative toxicity enhancement of ZnO NPs using a low-level laser of 405 nm wavelength (Ths-1220, China) for cowpea weevil control. Two batches of ZnO NPs were subjected to 15 and 30 minutes of laser irradiation. Irradiations were carried out in borosilicate glass test tubes using a 500 mW power laser beam spot of 4.0 mm. The 100 grams of non-infested cowpea samples were weighed in six replicates (R1, R2, R3, R4, R5, and R6) and a control. 90 active weevils (Callosbruchus maculatus) were obtained from an infested source of cowpea. The first batch of 15 minutes irradiated ZnO NPs was applied to the healthy beans in R1-R3, and the second batch of 30 minutes to R4-R6, likewise, the control. Replicates in the first batch registered weight losses between 0.70% and 1.20%, whereas the second batch showed minimal losses between 0.02% and 0.05%. By contrast, the control group experienced higher weight loss, between 1.10% and 2.80%. Statistical analysis via ANOVA did not reveal significant variations between groups and the Levene test indicated significant heterogeneity of variances (Sig. = 0.007). The application effect demonstrated a mortality rate of 99% compared to 70% in the 15-minute and 30-minute irradiated sample treatment groups, respectively, and 40% in the control group within 3 days.  It is plausible that the 15-minute exposure delivered a concentration of nanoparticles sufficient to induce acute toxicity, facilitating maximal interaction without oversaturation. Therefore, exhibiting ZnO NPs with promising insecticidal properties against weevils, resulting in optimal maximal mortality.