Improving Sphenophorus levis Adult Mortality with Solid Insecticide Applications and Increased Insecticide Dose

Abstract

Abstract The sugarcane weevil (Sphenophorus levis Vaurie, 1978) is currently considered the most important sugarcane pest in Brazil causing significant yield losses. Application methods of insecticides for S. levis control have not been effective mostly due to the insect’s habitat behavior bellow soil surface suppressing the correct placement of the insecticide active ingredient on target. Two experiments were conducted using a novel bioassay methodology that simulates sugarcane field conditions to effectively evaluate S. levis adult mortality and insecticide soil residue under different treatments. One study aimed to assess the efficacy of two liquid and solid applied insecticides while the second aimed to examinate the effect of increasing lambda-cyhalothrin + thiamethoxam dose on S. levis adult control. The novel bioassays simulated liquid and solid insecticide applications on sugarcane and exposed S. levis adults to residual rhizome and soil after insecticide application. In the first experiment, low S. levis adult control was detected (< 53% mortality) across all treatments where both solid and liquid applications of lambda-cyhalothrin + thiamethoxam provided greater efficacy levels than imidacloprid and control treatments, respectively. Solid applications promoted greater insecticide concentrations in soil during longer periods in comparison with liquid insecticide applications, providing maximum insect control levels at 7 days after application. In the second experiment, solid applications at higher insecticide dose significantly improved S. levis adult control (76.7% mortality) in comparison with results of recommended label rate for adult control (58.8% mortality).