Two distinct growth stages are occurring in Saskatchewan pea crops this year.
The 2005 season got off to a quick start on many farms as growers seeded in early April to reduce the risk of early fall frost. Then the cool wet weather came along, and the balance of pea seeding was delayed until late May and early June.
Powdery mildew in pea crops always relates to seeding date. Symptoms of the fungus typically appear around the middle of July in a normal year.
However, in past years, late seeding compounded the problem because the pods and seeds were not developed before the infestation occurred.
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The disease likes warm, sunny, dry conditions during the day, along with cool nights followed by heavy morning dew.
Early infections reduce the usable leaf area, cause stunted plants and affect the development of the pods and seeds.
The disease reduces yield, delays maturity and makes desiccation more difficult. It also leads to an increased occurrence of combine fires.
Symptoms include white, powdery spots on the lower leaves and stems. These spots eventually spread to the entire plant. Severely affected crops are covered in a white mat of spores with a bluish or silvery sheen. The underside of leaves turn yellow below the powdery infection.
On the positive side, heavy rain can wash some of the spores and infection off the leaves, resulting in less infection.
If conditions turn dry, producers are urged to scout their fields for powdery mildew.
Kumulus DF is a registered fungicide for the control of powdery mildew in dry pea production. This product is 80 percent sulfur, and will only protect non-infected leaves. It will not cure leaves that already have the disease.
Because of the high sulfur content, growers who use this product are cautioned to thoroughly flush their sprayers soon after application to prevent plugging.
