Some effects of oxamyl on the virus‐vector nematodes Longidorus elongatus and Xiphinema diversicaudatutn

SUMMARY Oxamyl applied to field soil prevented Longidorus elongatus from acquiring and transmitting tomato black ring virus for at least 6 wk, although numbers of nematodes were not greatly decreased compared with the untreated control. Glasshouse and laboratory tests examined the effects of oxamyl on viruliferous L. elongatus and Xiphinema diversicaudatum. In these tests oxamyl (1.0 ppm) in the soil water largely prevented L. elongatus transmitting virus to bait plants over a period of 1 month. X. diversicaudatum was equally affected by smaller concentrations, 0.1 ppm being sufficient to inhibit virus transmission in one test. Inhibition of virus transmission was associated with a decrease in the number of root tip galls produced by nematode feeding, especially that of X. diversicaudatum. Few nematodes were seriously affected by oxamyl, except at the greatest concentration tested (100 ppm), when numbers of L. elongatus, but not of X. diversicaudatum, were decreased. In vitro‐treated viruliferous nematodes protracted their stylets, but their subsequent ability to transmit virus was unimpaired.