The use of nematicides to control the spread of arabis mosaic virus by <i>Xiphinema diversicaudatum</i> (Micol.)

Abstract

SUMMARY Field experiments on three soil types in southern Britain showed that applying dichloropropane‐dichloropropene (D‐D) or methyl bromide at 2 lb./100 sq.ft. in summer killed over 99% of X. diver sicaudatum in soil and almost stopped the infection of strawberry crops with arabis mosaic virus (AMV). Both chemicals killed X. diversicaudatum down to 28 in., the greatest depth sampled. D‐D at 1 lb./100 sq.ft. gave variable results when applied in summer but was more effective when left in the soil through the winter. At the doses used, dazomet, methyl isothiocyanate, metham‐sodium, dibromochloropropane and tetramethyl thiuram disulphide killed too few X. diversicaudatum to control the spread of AMV. Incidence of AMV in crops planted on treated land was closely related to the number of surviving X. diversicaudatum. Larvae and adults seemed equally susceptible to the chemicals. In some experiments, other species of plant‐parasitic nematodes were sometimes less affected by D‐D than X. diversicaudatum. In untreated soil planted with strawberries, numbers of X. diversicaudatum tripled in 2 years, most of the increase coming in the second year. In D‐D treated soil, the few survivors appeared to increase even more slowly than this. A nematicidal treatment that brings the X. diversicaudatum population to fewer than one nematode per 2 1. of soil should not need repeating for several years.