September 5, 2018
Tree Q & A per the
Chouteau County Extension Office
• Why did two of my cottonwoods turn yellow in late July? According to Eva Grimme (MSU Plant Disease Diagnostician), symptoms are consistent with Marssonina leaf spot. Symptoms include dry, brownish lesions with yellowing borders. Margins are often irregular, indistinct, and not restricted by leaf veins. Infection is favored by wet weather, especially at the time when the leaves emerge from buds. Management includes pruning out, discarding, raking and destroying affected leaves. Water adequately during the growing season. When trees are...