Sensitivity of Meloidogyne incognita to pydiflumetofen

Abstract

Pydiflumetofen, a succinate dehydrogenase inhibitor fungicide, is being evaluated as a seed treatment in soybean to manage fungal diseases and plant-parasitic nematodes. However, there is currently no data on the toxicity of pydiflumetofen to M. incognita or its impact at low concentration on M. incognita infection of host roots. Nematode toxicity assays were conducted using aqueous solutions of pydiflumetofen, while root infection assays were conducted on tomato. Based on nematode motility, the 24-hr EC50 value for M. incognita was 207.9 μg/ml. When exposed to 1 μg a.i./ml for 24 h, there was no effect of pydiflumetofen on nematode motility, which was lower than the effect of fluopyram at 87%. Furthermore, no suppression of root galling was observed when second-stage juveniles were exposure for 24-hr to low concentrations of pydiflumetofen (ranging from 1.3 to 161.5 μg/ml) and subsequently inoculated on tomato plants. In a greenhouse pot experiment, seed-applied pydiflumetofen provided no suppression of M. incognita reproduction 60 d after inoculation on soybean. Overall, pydiflumetofen had no discernible effect on the motility or infectivity of M. incognita.