Evaluating the agronomic and economic benefit of including spinosad with and without pyrethroid insecticides in bermudagrass stem maggot treatments

The bermudagrass stem maggot (BSM; Atherigona reversura Villeneuve) is known to have a detrimental effect on bermudagrass (Cynodon spp.). Currently, two strategically timed pyrethroid applications are recommended for BSM suppression in each harvest cycle. However, producers are interested in applying spinosad because of its residual effects for other insects or reducing the number of pyrethroid applications to cut input costs. Therefore, the objective of this study was to determine the agronomic and economic implications of one or multiple pyrethroid (zeta-cypermethrin) and/or spinosad applications on ‘Alicia’ and ‘Tifton 85’ bermudagrasses. Generally, zeta-cypermethrin treatments resulted in a greater herbage accumulation compared to the untreated control in both cultivars. Regardless of cultivar, spinosad only treatments did not improve upon the herbage accumulation observed in the untreated control. Crude protein and total digestible nutrients were not affected by insecticide treatments in either cultivar. Finally, two zeta-cypermethrin applications resulted in greater net profit compared to other insecticide treatments. These data illustrate that there is not yet an alternative for two pyrethroid applications for BSM suppression. Ongoing research and breeding efforts are focused on BSM tolerance and reduced pyrethroid usage to prevent resistance to the insecticide.