For variety in your landscape, several trees and shrubs are available that feature yellow foliage instead of everyday green.
Grayish brown, sometimes rounded spots often cluster around the main veins of leaves. Heavily spotted leaves can become twisted and drop off the tree, which is when the blister problem may become obvious. The blister effect may not always be clear on these spots, but the spots are sometimes raised or curved.
Verticillium wilt is a fungal disease that affects over 300 species of plants, including many common trees and shrubs. In Iowa, it is most commonly seen on maple, ash, and catalpa trees, although it is also frequently found on smoke tree, viburnum, lilac, cherry, plum and several other trees and shrubs.
A condition known as bacterial wetwood occurs most frequently on elm, maple, poplar, oak and birch trees.