Barley Barley Crop Icon Brassicas Brassicas Crop Icon Sugar Beet Sugar Beet Carrots Carrots Icon Leeks Leek Icon Maize Maize Icon Oilseed Oilseed Icon Onions Onions Icon Other Cereals Other Cereals Icon O R T Peas And Beans Peas and beans Icon Potatoes Potatoes Icon Salad Crops Salad Crops Icon Soft Fruits Crops Soft Fruits Icon Top Fruits Crops Top Fruits Icon Wheat Crops Wheat Icon Calendar Calendar icon Arrow Next Arrow Previous Close Checkmark

Light Leaf Spot Identification and Management

Early leaf symptoms of light leaf spot

What is Light Leaf Spot?

Traditionally associated with Scotland and Northern England, light leaf spot is now widespread throughout the UK. Fungicides work best as protectants so early application at the first sign of disease in the autumn is essential. If crops are inadequately protected light leaf spot can spread through the plants affecting leaves, stems, flowers and pods. Untreated crops can suffer yield losses of 50% or more.

Later light leaf spot lesion

How to spot Light Leaf Spot

Large numbers of very small white sugar-type spores are visible on green leaf tissue either on the top or underside of the leaf. 

These quickly develop into discrete lesions with pinkish centres and many more of the spore-forming spots surrounding them.

Light leaf spot symptoms on pods

In the most severe cases whole leaves can be killed; these often do not abscise and instead remain attached to the plant. When disease pressure is intense, light leaf spot affects the developing leaves and buds causing plant stunting and leaf distortion.

Light leaf spot symptoms on stems

Infection will also progress from leaves onto stems and lateral branches. Elongated, fawn lesions, surrounded by black speckling will be seen. When conditions are humid white spore masses will also form on and around these stem lesions.

If the weather allows the disease to progress, pods are also affected. The whole raceme can become infected resulting in distorted pods that turn brown and may shatter prematurely or produce little yield.

How to control Light Leaf Spot

Varietal resistance to light leaf spot is the first line of defence, and so it is vital to consider growing a variety with a good resistance profile.

Cultivation techniques are also very helpful in controlling the disease. Burying stubble from previous crops in the vicinity of where new crops are being established reduces the risk of spores being blown on to current cropping area the new crop.

Proline (prothioconazole) is the strongest product for control of light leaf spot. Timely application is essential for effective control as fungicides need to be applied preventatively, which can be difficult given the weather conditions often prevailing at the right time for treatment.

Without any useful alternatives it is vital to protect the activity of triazoles such as Proline. Two applications are recommended; one at the first sign of infection in the autumn (often mid-late November) and another in winter or early spring. Higher rates should be used when disease pressure is severe, if there is a history of reduced azole sensitivity or in high disease risk areas.


Would you like to check your OSR leaves for LLS?

Well you can for free thanks to SpotCheck, an initiative to provide growers with a conclusive diagnosis of light leaf spot and other diseases' prevalence in oilseed rape crops.

View now

Related articles