Measuring Sugarcane Aphid Susceptibility for Sulfoxaflor and Flupyradifurone

Bioassays were conducted to measure sugarcane aphid, Melanaphis sacchari (Zehntner) susceptibility to Transform (sulfoxaflor) and Sivanto (flupyradifurone).  Methods were adapted from those described by the Insecticide Resistance Action Committee (IRAC, Method No. 019).  The bioassay arenas consisted of individual 29-ml Solo condiment cups with a 2mm layer of 1% agar solution in the bottom.  A 3 cm diameter hole was cut into each lid and sealed with a piece of single ply tissue paper to allow excess moisture to escape.  The commercial formulation of sulfoxaflor and flupyradifurone was used to prepare a series of insecticides for bioassays.  The insecticide concentrations tested included: 0.0, 0.5, 2, 5, 10, 15, 25, and 35 ppm active ingredient.  Insecticides were diluted in water to obtain 500 ml of solution at the various concentrations.  A non-ionic surfactant (Induce, Helena Chemical) was added to each solution at a rate of 0.5% v:v to ensure even distribution across the surface of the leaf disc.  The LC₅₀ values ranged from 0.583 to 14.772 ppm with a mean of 4.70 and a median of 3.867 for sulfoxaflor.  The LC₅₀ values for flupyradifurone ranged from 0.380 to 15.491 ppm with a mean of 8.36 and a median of 8.96.