24 October 2011
Check grass leys for the fungal disease Drechslera leaf spot as high levels have been seen in variety and grazing trials warns NIAB TAG. If left unchecked the disease can damage leys, reducing the quality and value of late season grazing.
NIAB TAG’s Yorkshire-based trials manager Peter Burgis has seen over 40% leaf area infected with the disease in variety plots and significant levels in on-farm grazing trials. “Cattle are rejecting the badly infected varieties, which leads to excessive growth and more disease build-up. Drechslera leaf spot can persist in cold weather leading to further winter damage. Infected material needs to be topped, or grazed more tightly with sheep before going into the winter,” he advises.
Several species of Drechslera can infect perennial ryegrasses. Symptoms include brown spots surrounded by yellowing tissue, while others show distinct brown netting lesions, similar to those caused by net blotch on barley. The causal organisms are closely related, but do not cross-infect from ryegrass to barley or vice-versa.
“The disease can appear quite insignificant, though just one or two spots will often kill the entire leaf. However, when the disease increases to produce a widespread blight, the effects on a sward can be dramatic,” warns NIAB TAG pathologist Dr Jane Thomas.
Drechslera can also occur in the spring, but tends to decline during the summer months before resurfacing in the autumn, particularly on grass that has been left to grow late season. It can be found in most regions of the UK, and tends to be more serious in cool and wet conditions.
Dr Thomas notes that Drechslera has been a frequent problem in the past few years, with some varieties particularly susceptible. “These susceptible varieties will need appropriate management, preferably used in mixtures with more resistant types to avoid serious infections.”
Information on the resistance of perennial ryegrass varieties is available from seed merchants contributing to the Grass Levy Scheme. The scheme is also supported by BSPB, EBLEX and DairyCo.
Dr Jane Thomas, Head of Disease Resistance and Diagnostics, NIAB TAG
T: 01223 342251
Ros Lloyd, Communications Manager, NIAB
T: 01223 342313
M: 07711 568164