Sensitivity to fluensulfone of inactivated Meloidogyne spp. second-stage juveniles

Nonfumigant nematicide efficacy is affected by several factors, such as nematode species and environmental conditions. However, the influence of nematodes' physiological status on nematicide efficacy is unknown. Inactive nematodes, such as those in quiescence or dormancy, seem to be more tolerant to nematicides than active ones. Second-stage juveniles of Meloidogyne species were inactivated by low temperatures and reversible nematicides before and during exposure to fluensulfone. The sensitivity of inactive juveniles to fluensulfone the nematicide was compared to that of active juveniles by EC₅₀ (median effective concentration) for juvenile immobilization and root gall reduction.

Inactivating Meloidogyne hapla and Meloidogyne javanica juveniles at 5 °C increased the EC₅₀ (median effective concentration) of fluensulfone for immobilization of and root galling by Meloidogyne spp. 3.6 to 9.5 times. When the exposure temperature was decreased from 25 to 15 °C, EC₅₀ for M. javanica root gall reduction after 24 and 48 h exposure increased 3.1 and 4.9 times, respectively, whereas for M. hapla, it increased 2.3 and 2.0 times, respectively. Juveniles of M. javanica and M. incognita immobilized by fenamiphos were as sensitive to fluensulfone as active juveniles based on the number of root galls. However, juveniles of these species immobilized by fluopyram were more tolerant to fluensulfone than untreated active juveniles. An interaction of fluopyram and fluensulfone activities is suggested.

Changes in the sensitivity of inactive Meloidogyne spp. juveniles to fluensulfone depend on the inactivation method. Fluensulfone could be better applied when nematodes are active in the soil. © 2020 Society of Chemical Industry.