Impact of granular carriers to improve the efficacy of entomopathogenic fungi against wireworms in spring wheat

Wireworms are a major concern for wheat growers and several other crops around the globe. Environmentally friendly management strategies are needed because the present conventional chemical seed treatments can be ineffective and pose environmental risks. While biological control of wireworms in a general sense has not been practical, use of entomopathogenic fungi (EPF) is one environmentally friendly solution for this problem. In 2017, granular formulations of three EPFs, on polenta and millet spent substrate carriers, were applied in furrow at planting, at two rates, against a water control and imidacloprid seed treatment in spring wheat in Montana, USA. The selected EPFs were Beauveria bassiana GHA, Metarhizium robertsii DWR356, M. robertsii DWR2009, applied as granular formulations at 11 kg ha−1 or 22 kg ha−1. In 2017, at Valier, DWR356, DWR2009 on millet carrier at 22.4 kg ha−1 provided greater yield, but all the treatments at lower rate were still cost-effective. In 2018, B. bassiana GHA and M. robertsii DWR2009 were retested along with B. bassiana ERL836 and M. brunneum F52. Millet carrier alone, GHA and ERL836 on millet carrier obtained cost-effective results at irrigated and non-irrigated sites in 2018. However, these were less cost-effective than imidacloprid as a seed treatment. The overall cost–benefit ratio of using EPF granules was higher in both the years compared to control. Millet on which the fungi were grown worked better than the other carriers. Further evaluation of the effect of the carrier while applying EPFs in furrow as granules is required.