Toxicity assessment of selected novel fungicides on the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) in stored wheat grain

摘要

The lesser grain borer, Rhyzopertha dominica, is considered a critical, global pest of stored cereal grains especially wheat cereal grains. Developed a new strategy to control it was a paramount. Herein, we evaluate the toxicity of selected novel fungicides, thiophanate-methyl 70% WP, methylbenzimidazole 50% WP, myclobutanil 10% WP, iminoctadine 40% WP, carbendazim 50% WP, and fenbuconazole 5% EW on R. dominica adults after 24, 48, 72, 96, 120, 144, 168-h exposure under laboratory conditions. As results, after 24-h exposure, thiophanate-methyl was considered the most toxic fungicide with LC50 and LC90 values of 0.56% and 2.56%. Fenbuconazole was the lowest toxic one among the tested compounds (the LC50 and LC90 values were 62.53% and 90.82%). Little changes after 48-h exposure, iminoctadine was the most potent fungicide among the selected fungicides with LC50 and LC90 values of 0.19% and 1.36%, whereas fenbuconazole still exhibited the minimal toxicity pesticides among the tested compounds (the LC50 and LC90 values were 52.87% and 96.48%). Noticeably, the same trend was revealed at the rest of the experiment especially after 168-h exposure. Based on the slope values of the tested fungicides, R. dominica revealed relative high homogeneity response to the fenbuconazole (4.40) after 168-h exposure, and low homogeneity to the remainder of the tested fungicides (slope values ranged from 0.11 to 0.57). According to the LT50 values, thiophanate-methyl and iminoctadine showed high efficiency against R. dominica adults (30.33 and 35.07 hours), and carbendazim was the least effective (119.23 hours). Acquired effects that obtained can deliver a better knowledge to the stored grain managers regarding to the prospective selected fungicides to control R. dominica.