Evaluating fipronil as a seed dressing for lucerne crown borer (Zygrita diva) management in soybeans – 2015/16 and 2016/17

Abstract

Key findings •• Soybean yields were reduced by 50% and seed size by 16% on untreated seed compared with seed treated with fipronil (e.g. Legion®), in 2015. •• Where lucerne crown borer (LCB) infestation was heavy, fipronil seed treatment at 100 mL/100 kg of seed reduced infestation levels from 86% to 38%, girdling (stem ring barking) from 70% to 21% and plant lodging from 31% to 5%. •• Fipronil seed dressing had no negative effect on nodulation. •• Crop senescence was hastened where seed was untreated or low concentrations of fipronil were used. •• Crop maturity was delayed by up to eight days in healthier crop protected from LCB by high concentrations of fipronil seed dressing. •• Where LCB pressure was low, the fipronil concentration had no significant effect on yield or quality.