Archive:Poplar/Septotinia Leaf Blotch

From Bugwoodwiki

From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.

Importance

Infection of Septotinia results in extensive leaf necrosis and premature defoliation that can damage young trees in plantations and nurseries.

Look For:

• Small brown spots on leaves in spring.

• Large blotches with irregular margins and gray centers in midsummer to late summer.

• White spore-producing structures (sporodochia) and masses of spores (conidia) in concentric circles on the surface of the blotches.

Diseased Leaves

Biology

The fungus overwnters as hard, black bodies (sclerotia) on infected fallen leaves. In the spring, ascospores from fruit bodies (apothecia) in the sclerotia are discharged into the air during wet weather. Spores are carried by wind and rainsplash to developing leaves, where infection takes place. Secondary infections result from conidia that develop within leaf spots being rainsplashed to adjacent leaves. Disease is most common and severe in closely spaced plantings and dense nursery beds where moisture is retained longer on leaf surfaces because of the reduced air movement.

Control:

• Direct control is usually not necessary.

• Wider tree spacing and removal of infected leaf debris in late fall or early spring before spore discharge will reduce disease.

Sporodochia. (White spots within leaf blotch.)

Conidia

For Additional Information:

Ostry, M.E. 1980. How to identify Septotinia and Phyllosticta leaf spots of poplars. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station. 6 p.