Tatters

A cynipid wasp may form galls that deform foliage and shoots. Current year’s galls are green; one-year-old galls are black. This wasp is most commonly observed infesting white oak. Severe damage is rare; there is no known treatment. The foliage in the right half of this photo is infected with a fungal disease known as anthracnose.

Anthracnose, a disease caused by the fungus Discula sp., may infect leaves and cause brown to black spots on leaf edges and along leaf veins. Anthracnose may cause some twig mortality and is most common during cool, wet springs. Significant injury rarely occurs. Rake and dispose of infected leaves to minimize spread.

Since the early 1990’s, White and Bur oaks in southern Wisconsin have shown the symptoms of a phenomenon called “tatters”. Although the cause of tatters is not definitive, there appears to be a relationship between cold temperatures occurring during bud and leaf expansion and the appearance of tatters. Symptoms appear in mid-late May. Tatters may occur in oak woodlands or on single yard trees. Red and black oaks typically do not show symptoms. Affected trees are scattered on this hillside. Tattered trees have very thin foliage and may appear to be without foliage from a distance.

Symptoms on Bur oak associated with oak tatters. Note the absence of tissue between the veins.

This branch shows tattered foliage and new, uninjured foliage. If tatters affects a high percentage of foliage, refoliation will occur 2-3 weeks following the appearance of tatters. Although refoliation can stress a tree, spring is the best time for this to occur. The tree has the rest of the growing season to replenish its starch reserves.