Anti-sclerotinia sprays, omitted by many oilseed rape growers to their regret last season, should be easier to justify this season.

Soil temperatures have generally been too low for much germination of the disease’s sclerotia, but early petal testing indicates some activity, warns ADAS pathologist Peter Gladders. “There is something happening.”

Last year’s uncontrolled infections, often caused by delayed weather-hit spraying programmes, left plenty of sclerotia in fields. The dry windy April also distributed the disease’s spores more widely, notes Masstock‘s David Langton. “The effect is that although germination hasn’t started, most crops are at significantly higher risk than for many years.”

TAG‘s David Parish, who agrees sclerotinia pressure is greater than usual, estimates only 50% of growers applied specific treatments last season. “Last year showed that our ability to assess the risk based on the weather is not very reliable. My advice this year for anyone with oilseed rape regularly cropped is that it would be prudent to invest in a sclerotinia spray.”

High oilseed prices mean guarding against sclerotinia should be well worthwhile.

At current prices it needs only 100kg/ha extra to cover the treatment cost, adds Mr Langton. “And in high risk areas, like Romney Marsh and Herefordshire, I think people should consider more than one spray, especially if they didn’t get good control last year.”

Growth regulatory fungicides at yellow bud offer some protection, notes Dr Gladders. “But the effects last only about three weeks.”

So growers faced with protracted flowering in high risk areas, namely those having crops with 20% or more plants infected last year, may need a mid-flowering follow up, he suggests. “Very few have done that in the past, but it may be necessary if we get a long campaign.”

ProCam‘s Dave Ellerton says early flowering sprays worked particularly well last spring. “The trouble comes if you wait and then the weather clamps down.” A wide range of products is available, but Filan (boscalid) supplies could be tight, he says.

Colleague Nick Myers describes anti-sclerotinia treatment at current prices as a “no-brainer”. The key is to use plenty of water – at least 200 litres/ha – to ensure good canopy penetration and stem coverage, says Mr Langton.

Sclerotinia threat

• High disease pressure
• Better value crops
• Two sprays for high risk?
• Keep volumes up