Preliminary glasshouse and field tests of soil partial sterilants for clubroot control

Abstract

Experiments were made on field plots and in individually dosed pots to investigate the effects of ten soil partial sterilants on percentage infection of cabbage with clubroot. Additionally, cores of naturally-infested soil or samples of artificially infested and buried soil removed from some treated plots were also sown with cabbage in a glasshouse and the seedlings then assayed for the presence of clubroot. There was evidence that the partial sterilants were optimally effective at different depths. Dowfume M.C.2 and Basamid having the unique properties of effectiveness at deep and shallow horizons of the soil respectively. Chloropicrin at 60 d i m z and Dowfume M.C.2 at 98 g/m2 were the most effective partial sterilants in controlling clubroot while Basamid and Telone were also considered to merit further testing. All other partial sterilants reduced percentage infection in pot experiments and field crops to varying extents although formaldehyde was least effective.

Control of lettuce big‐vein disease by soil sterilisation

“…Metham sodium prevented infection and symptom expression at half the recommended field dose and showed activity down to one eighth the field dose. However, past experience with methyl isothiocyanate generators (Buczacki and White, 1977) suggested that the downward penetration of the gas would be insuflicient to give complete or lasting control of a soil-borne disease in the field. Metham sodium at 1 or 2 X field dose was phytotoxic even though a cress test had indicated absence of residual methyl isothiocyanate.…”

“…Studies on the control of clubroot disease {Plasmodiophora brassicae Wor.) by soil sterilisation (Buczacki and White, 1977) showed that although the results of small scale tests tended to over-estimate the efficacy of treatments, tests based on decreasing dosages to a quarter or an eighth of the field dose tacihtated the selection of the most active chemicals.…”

“…The bags were sealed and the soil m each bag agitated to ensure thorough mixing. Each chemical was apphed at five rates, based on a similar experiment by Buczacki and White (1977): 0-125, 0-25, 0-5, 1-0 and 2-0 x the normally recommended field dose. There were five replicates of each treatment.…”

The value of soil sterilants for the control of clubroot on a field scale

“…After a cress test (Buczacki and White, 1977) to confirm the absence of phytotoxic residues, seeds were drilled on 31 May at 15-cm spacing in rows 30 cm apart. At harvest on 23 October, 50 plants were taken at random from each plot and the head weights and numbers with clubroot symptoms were recorded.…”

“…Previous accounts (Buczacki and White, 1977;White and Buczacki, 1977b) described the use of soil sterilants including dazomet and 1, 3-dichloropropene for the eradication of small infestation foci of the clubroot causal organism, Plasmodiophora brassicae Wor. In those studies the treatment cost, although large, was considered to be unimportant when weighed against the possibility of preventing the spread of the disease from the infested areas to uncontaminated land.…”