Fungus on Yellow Poplars

Leaf Rust

Early summer may bring leaf rust to yellow poplar trees, a type of fungus that creates yellowish spots on the upper surface of the leaves. Pustules, yellow to orange in color, may be visible on the undersides of leaves. The pustules are actually spores, which may be transmitted by wind to other trees nearby. In late summer and fall, the pustules turn from yellowish-orange to brown and black. The fungus creates much more severe cosmetic problems for the tree, potentially causing distorted growth and premature leaf drop. Moisture and humidity fosters the growth of leaf rust, while hot, dry weather reduces the appearance of the fungus.

Leaf spot may make its presence known on foliage through four different symptoms: small flecks, white or silver spots, brown and yellow spots and asymmetrical tan and brown spots. The fungus causes leaves to drop from the tree prematurely and may spread from tree to tree as time goes by. Control leaf spot fungus by removing infected leaves and stems from the tree completely. It's important to deal with leaf spot fungus immediately, as it does not affect only yellow poplar trees.

Shoot blight damages young shoots and leaves on yellow poplar trees. The affected shoots will shrivel up and turn black. Shoot blight is found in trees that are exposed to shade and moisture, and it is not severely damaging to trees unless it persists through several growing seasons. Prune away infected shoots when they appear on the tree; if this has no effect, spray trees with copper fungicide every 10 days.

Cankers are caused by parasitic fungi that kill bark on the branches and trunks of yellow poplars. The resulting bare, dead patches of the tree are the cankers. If enough of these cankers appear on the tree, it may die. Canker fungi may spread through spores, finding small cracks and scars on the tree and taking root. Dark, odorous sap comes out of the cankers. The cankers may begin to heal themselves, creating thick ridges around the edges of the bare patch. Prevent cankers by supplying trees with adequate moisture, as drought helps to facilitate the growth of the canker-causing fungus. Prune away cankers and treat with fungicidal wound dressing.