Effects of Host Plant Cultivar and Insecticide Type on Rice Damage and Growth of Chilo suppressalis (Lepidoptera: Crambidae) Larvae in Semi-field Conditions
Chilo suppressalis is a major pest of rice in most regions of Iran and across the world, resulting in "dead heart" and "white head" damage in rice crops. The present study was conducted as a factorial randomized complete block design in Amol County, Iran, in five repetitions for treatments including "rice cultivar" in two levels of Tarom Mahali and Shiroodi, and "insecticide" in four levels of cypermethrin, tebufenozide, diazinon (in two forms of 10% granule and 60% emulsion), and an insecticide-free treatment. Investigating the insecticide treatments, cypermethrin showed the lowest mean percentage of dead heart and white head (8.12 and 14.35%, respectively). In the present study, the Shiroodi cultivar developed a higher resistance to C. suppressalis damage compared to the Tarom Mahali cultivar. Comparing the insecticide efficacy, tebufenozide showed the most progress in reducing C. suppressalis damage in-between the growth stages of rice. Cypermethrin is a carcinogenic substance, hazardous to both the environment and natural enemies. On the other hand, the application of diazinon has led to increased damage in rice cultivars due to its lower efficacy against C. suppressalis. Therefore, tebufenozide could be considered as an alternative and specific insecticide for the control of C. suppressalis in Iran.