Determination of malathion toxicity against Sitophilus oryzae (L.) and Sitophilus granarius (L.) (Coleoptera: Curculionidae) populations under different temperature conditions
摘要
Sitophilus oryzae (L.) and Sitophilus granarius (L.) (Coleoptera: Curculionidae), globally recognized as highly destructive pests to stored grains, have prompted the prevalent use of chemical insecticides for their management. Malathion, an essential organophosphate insecticide, has historically played a pivotal role in stored-product pest management. However, the residual efficacy under specific conditions has raised concerns on its efficacy. To explore variations in lethal concentrations due to varying temperature, the susceptibility to malathion of S. granarius and S. oryzae populations from diverse geographical locations in Türkiye was assessed. A dose-response of malathion applied onto the insect was assessed at 25 °C and 30 °C. Under a spray tower, insects were exposed to malathion that contained 2 mL of malathion and distilled water mixture. Mortality was monitored using the dry film method every 30 min for 12 h. Among the S. oryzae populations at both 25 °C and 30 °C, the IN5 population was the most susceptible to malathion application with LT50 values of 5.12 and 2.82 h, respectively. Similar results were recorded for S. granarius in the PO7 population and the corresponding LT50 values as 5.94 and 3.83 h. Temperature increase accelerated the mortality, leading to a 1.24-1.86-fold increase in S. oryzae populations and a 1.03-1.62-fold increase in S. granarius populations. These findings suggest that malathion remains a viable option for controlling these stored insect pests. Future research should explore different conditions to determine optimal parameters for its effectiveness.