Non-target potential of neonicotinoid and fungicide seed cane treatments on Solenopsis invicta.

Traditionally, Louisiana sugarcane has been grown vegetatively from whole stalks, but innovations in machinery and rising labor costs have increased interest in billet planting. Billets, short stalk pieces containing several viable eyes, are more susceptible to pathogen exposure and may require fungicide and/or insecticide applications at planting to increase stand potential. Work in other crops indicates such treatments may alter arthropod predator abundance, so the goal of this study was to evaluate the potential non-target effects of select treatments at planting on the red important fire ant (RIFA), Solenopsis invicta , and other arthropod predators of the sugarcane borer, Diatraea saccharalis , in sugarcane. We sampled predators and measured biological control potential in plots treated with a neonicotinoid insecticide and/or fungicide applied as in-furrow sprays or seed cane dips. We then assessed RIFA worker survival and behavior following 48 h exposure in the laboratory. With the exception of one in-furrow sprayed field trial, treatments did not significantly impact RIFA numbers. Treatments did not impact the abundance of other predator groups or biological control potential (borer damage and sentinel egg predation) in any field trial. Laboratory assessments indicated no treatment effect on RIFA behavior metrics after exposure but had mixed results on survival depending on application method. Our data indicate that these seed cane treatments may not disrupt biological control and the greater epigeal arthropod predator community in Louisiana sugarcane. However, tests should be replicated under different environmental conditions to ensure biological control, particularly by RIFA, is maintained with larger-scale use. • Pesticides at planting may increase billet-planted sugarcane stand potential. • Such treatments can interfere with biocontrol through lethal and sublethal effects. • Thiamethoxam, azoxystrobin and propiconazole didn't diminish sugarcane biocontrol. • Thiamethoxam may diminish fire ant survival but not other predators' abundance. [ABSTRACT FROM AUTHOR]