Being exposed to low concentrations of pirimiphos-methyl and chlorfenapyr has detrimental effects on the mobility of Trogoderma granarium.

Background: Sublethal effects of insecticides may negatively affect several biological and behavioral traits of insects. The lethal effects of pirimiphos-methyl and chlorfenapyr have been previously showed on Trogoderma granarium, but little knowledge is available about their sublethal effects at low concentrations on both sexes. Herein, the sublethal effects of pirimiphos-methyl and chlorfenapyr on the mobility of T. granarium males and females were investigated.

Results: Lethal concentration (LC) values of pirimiphos-methyl and chlorfenapyr were lower for T. granarium females than males. LC values on males were LC  = 0.000788 and 0.00139 mg active ingredient (a.i.) cm , LC  = 0.00350 and 0.00535 mg a.i. cm , and LC  = 0.00986 and 0.0136 mg a.i. cm for pirimiphos-methyl and chlorfenapyr respectively. LC on females were LC  = 0.000704 and 0.00110 mg a.i. cm , LC  = 0.00323 and 0.00428 mg a.i. cm , and LC  = 0.00925 and 0.0110 mg a.i. cm for pirimiphos-methyl and chlorfenapyr respectively. The walking duration of beetles exposed to LC of pirimiphos-methyl was significantly lower than the individuals exposed to LC and LC of both insecticides and control ones. Pirimiphos-methyl LC -exposed males remained more time on their back (101.7 s) than females (46.9 s), while the latter stayed immobile longer than males (381.7 s versus 371.9 s). The highest speed was recorded for control beetles (14.17 mm s females vs. 12.44 mm s males), while the lowest speed was observed in pirimiphos-methyl LC -treated males (8.36 mm s ) and females (9.66 mm s ).

Conclusions: Overall, males and females exposed to low concentrations of pirimiphos-methyl and chlorfenapyr showed reduced motility. This knowledge can be exploited further to unlock behavioral effects of insecticides for effective pest management programs in warehouses. © 2023 Society of Chemical Industry.