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Barley Powdery Mildew
Blumeria graminis
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General Description
Powdery mildew is one of the major diseases affecting barley. There are currently many spring barley varieties which show good varietal resistance, but the popular malting barley variety Optic is very susceptible to this disease. With so much of the spring barley area using this variety, it has led to an increase in this disease in recent years.
The disease, which affects both winter and spring varieties, produces a white fluffy fungal growth on the leaf surface. This can cause leaves to turn yellow, leading to a loss in green leaf. High levels of disease at an early crop growth stage can kill out tillers. Many varieties show adult resistance, including Optic. This means disease levels are generally lower later in the season.
Biology
The disease is known as a biotroph which means it requires a living host to survive. A typical symptom of powdery mildew is white fluffy superficial fungal growth on the surface of leaves, stems and ears. Fungal spores which develop from these lesions are spread to other plants via the wind. The ideal infection conditions are mild and humid. Very wet conditions can limit the spread of the spores.
The disease can also overwinter in crop trash in black fungal bodies known as cleistothecia. Cereal volunteers are another method of survival. The 'Green Bridge' allows powdery mildew to spread from a winter sown crop in the autumn, to the spring sown crop in the spring, to late developing volunteers before infecting the following winter barley crop.
Advice
Diary
April
Stem Extension Fungicide Treatment Is key For Winter Barley
The stem extension (GS31-32) fungicide treatment is a key fungicide timing in winter barley. More...
Watch for early mildew in spring barley crops
Popular malting spring barley varieties, including Optic and Oxbridge are susceptible to powdery mildew. More...
May
Disease Protection At Mid Tillering
With crops sown in March now tillering, it is time to consider a fungicide to protect crops from disease. More...