Oilseed rape damage could heighten sclerotinia disease risk

Oilseed rape crops suffering from split stems and flea beetle larvae damage could be at high risk of sclerotinia disease this spring.

Rapid stem extension growth causing split plant stems and damage from cabbage stem flea beetle larvae emergence can cause an easy entry for the disease, growers are being warned.

“Sclerotinia does get into oilseed rape plants through wounds, but it depends on how extensive the damage is in crops,” says Caroline Young, plant pathologist at crop scientist group Adas.

See also:  Spray timing is key for sclerotinia control in oilseed rape 

Inspect crops, farmers urged

With oilseed rape crops in southern England starting – or about – to flower and with disease inoculum around, she advises growers to examine crops for damage.

Oilseed rape plant with split stem

The stem of a growing oilseed rape plant has split.

“If the damage is extensive, we would advise growers to apply a protectant fungicide at early flowering,” Dr Young adds.

Generally, fungicides need to be applied before significant petal fall as the pathogen can use decaying petals as a food source to develop.

Fast growth

Simon Roberts, Syngenta’s field technical manager, says the group’s trial plots in Hampshire have grown in height by more than 60cm in less than two weeks.

“Typically such rapid growth results in weak stems with a greater frequency of splits and breakage at the axial leaf joints,” he says.

Diseased oilseed rape plant

Sclerotinia infection on a green stem of oilseed rape.

In addition, many crops have a lot of holes appearing in stems around the leaf axial joints where flea beetle larvae are burrowing out from the plant stems.

Any damage to the plants allows sclerotinia to get in, especially if spore presence coincides with petal fall, Mr Roberts adds.

The disease will exacerbate any weakness in stems, leading to yield loss from extensive canopy collapse and early die-back, he says.

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