Treat rhizoctonia to increase skin quality
By Louise Impey
Tackling rhizoctonia effectively is taking on greater significance for Greenvale AP”s David Lawson following more customer emphasis on skin quality. And that means using a seed treatment, rather than the alternative foliar treatment.
“It”s not just the blemish on the tuber surface,” says Mr Lawson, who grows for the pre-pack market in the Scottish borders. “The fungus can infect developing sprouts and stolons before emergence, resulting in cankers, delaying emergence and producing an undesirable tuber size distribution.”
The disease gets into plants from both seed and soil-borne inoculum, he says. A seed assessment can be carried out before planting to test for rhizoctonia and black scurf, but there”s no way of predicting which fields harbour the greatest infection levels.
“Our policy is to use a seed treatment where there”s a risk, especially as we don”t always know the full history of the ground we rent,” says Mr Lawson.
“Wide rotations and control of groundkeepers are a good start for soil-borne disease control; the alternative is to spray Amistar (azoxystrobin) onto the soil, but that”s very expensive if you don”t have a severe problem.”
Last year, he treated all the infected seed with RhiNo (flutolanil), a new seed treatment from Certis. “The launch of RhiNo coincided with Monceren (pencycuron) liquid losing its approval, and I was less happy about using the dust formulation of Monceren.”
APPEAL
Part of the appeal of RhiNo is its slight systemic effect, which means that the growing stolons are given some protection from infection. “It seems to help protect against the soil-borne inoculum. It”s important to get the plant up and through the ground quickly if you want to prevent rhizoctonia.”
Rhizoctonia is favoured by cold, wet springs when crops are slow to emerge, allowing the disease to get into the growing tip before the plant is through the ground, he says.
“Last year, there were no signs of black scurf or rhizoctonia following RhiNo use, although growing conditions were very good last spring so the plants had a good chance of avoiding the disease.”
At 18/t, RhiNo costs about the same as other treatments, and considerably less than Amistar, he calculates. “I will be using it again this season,” he confirms. “It”s the best solution for our situation at the moment.”