Control of lettuce big‐vein disease by soil sterilisation

Abstract

SUMMARY Lettuce plants grown in the glasshouse in big‐vein‐contaminated soil previously treated with methyl bromide at 125–2000 kg/ha (x 0.125– 2.0 the dose used in the field) did not develop big‐vein symptoms, although at dosages up to 500 kg/ha their roots were infected by Olpidium brassicae(Wor.) Dang., the vector of the disease. Soil treatment with dazomet, chloropicrin, 1, 3‐dichloropropene or metham sodium gave symptom‐free plants at doses corresponding to those normally applied in the field. When applied to contaminated field plots, methyl bromide at 750 or 1000 kg/ha controlled the disease, but 10 per cent of plants showed big‐vein symptoms in plots treated at 500 kg/ha. All methyl bromide treatments significantly increased lettuce head weight compared with the untreated controls, and resulted in bromide residues in the plants of 2300–5300 ng/g of dry tissue compared with 30 μg/g in plants from untreated plots. Plants were harvested 12 weeks after completion of methyl bromide application, by which time there was evidence of leaching of bromide from the upper 10 cm of soil.

The use of methyl bromide and carbendazim for the control of lettuce big‐vein disease

“…Bromide residues in lettuce heads at the first harvest after methyl bromide treatment were almost double those in an earlier experiment (White, 1980), although even the higher values were lower than some reported in papers reviewed by Hoffmann & M,alkomes (1979). It is possible that the cooler, wetter conditions encountered by this crop permitted increased uptake of bromide ions.…”

“…Pievious experiments (White, 1980) showed that the lettuce big-vein disease could be eliminated from soil contaminated with the big-vein vector Olpidium brassicae (Wor.) Dang, if treated with methyl bromide at 750 kg/ha.…”

“…0032-0862/83/0600-0151 $02.,00 '^' t983 British Society for Plant Pathology on big-vein control during repeated cropping after a single methyl bromide treatment. Because of tlie high levels of bromide ions found in lettuce plants in previous work (White, 1980) the bromide residues in plants and soil were measured throughout this experiment. In addition, the effects of incorporating carbendazim into peat blocks in which lettuce plants veie raised prior to transplanting in the field were studied, since Tomlioson & Faithfull (1979a, b) had shown that this treatment prevented the disease developing in lettuce crops grown in nutrient film culture.…”

“…Since other soil sterilants are less effective than methyl bromide (Campbell et al, 1980;White,, 1980), it is unlikely that significant further progress will be made in the control of big-¥ein disease until new, more effective chemicals are available, or until a source of disease resistance has been found.…”

Applied Plant Virology

“…Injection of methyl bromide into contaminated field soils has been successfully used to control big-vein disease of lettuce, which is transmitted by Olpidium brassicae (White, 1980(White, , 1983Campbell et al, 1980). The disease may also be controlled by incorporating carbendazim (methyl-2-yl-benzimidazole carbamate) into peat-blocks used for lettuce transplants, prior to transplanting in big-vein contaminated soil (White, 1983).…”