Control of Verticillium wilt and other soil-borne diseases of strawberry in Britain by chemical soil disinfestation.
Dazomet (380 and 570 kg/ha) and chloropicrin (75, 150 and 300 litres/ha) were compared as preplanting soil treatments for control of V. dahliae and other benefits in a commercial planting of Elsanta strawberries grown on raised beds mulched with polyethylene. Metham-sodium (260 kg/ha) and 1,3-dichloropropene (210 litres/ha) were included as non-replicated, observational treatments. Wilt incidence at the end of the first season was 4.7% in untreated beds and <1% in all main treatments. Wilt incidence in metham-sodium and 1,3-dichloropropene treated beds was 1.6 and 0%, respectively. Both dazomet treatments, metham-sodium and 1,3-dichloropropene caused high nematode mortality in treated soil; the effect of chloropicrin was related to dose. Only dazomet (380 kg) gave significant weed control. Yield data from a sampling band across the field showed no effect of treatment in the first season, although whole-bed data showed small but significant (P<0.05) effects of dazomet (380 kg) and chloropicrin at 150 and 300 litres/ha. Metham-sodium treatment gave yields similar to the best main treatments but 1,3-dichloropropene treatment resulted in a low yield. Post-harvest plant size was significantly affected by all main treatments. Pre-planting soil from all main treatments had higher mineral nitrogen content than untreated soil. In the second season wilt control was maintained by all treatments while the incidence in untreated beds had doubled. Two Phytophthora diseases, red core (P. fragariae) and crown rot (P. cactorum), which occurred unexpectedly in the trial, were reduced significantly by 380 kg dazomet. There was no significant effect of treatment on crown number, but yield was significantly improved by both rates of dazomet and by 300 litres chloropicrin. Yields from the metham-sodium and 1,3-dichloropropene treated beds were 92 and 68% of those from untreated beds. Yields in the second season were most closely correlated with red core severity.