VARIED establishment of oilseed rape crops last autumn, could result in a protracted flowering period in areas across the UK, leaving crops susceptible to sclerotinia infection over the coming weeks.
With AHDB Cereals and Oilseeds reporting that levels of sclerotinia are medium to high in some locations, Chris Charnock, Certis’ arable product manager, warned this week of the risks following recent good weather.
“Due to the dry conditions seen in the autumn, OSR crops experienced protracted establishment, with crops looking very patchy,” explained Mr Charnock. “As a result, many growers are experiencing irregular flowering, with crops at varying growth stages within the same field.
“Most growers may have carried out an initial protectant spray, however this prolonged flowering period, increased temperatures and intermittent rainfall, will encourage petal fall and, with it, the risk of disease,” he added.
Caused by the fungus sclerotinia sclerotiorum, which releases spores from the base of the crop to coincide with petal fall, which leaves a scar on the plant as an entry point for infection. This, along with warm and humid weather conditions, can cause the disease to flourish.
“As a result, growers should consider carrying out a second spray of a product containing thiophanate methyl, such as Topsin or Taurus, 10 to 14 days after the initial spray. This will provide continued protection against sclerotinia for the prolonged flowering period that we are experiencing,” said Mr Charnock.
“Managing crops at varying growth stages can add complexity to spray programmes, but an assessment of all known factors and a good understanding of treatment options, will aid growers in protecting their crops at times of increased disease pressure.”