QuestionYesterday I asked a question about a cottonwood problem. You sent an email saying you answered my question and to look on this site...but there is no answer to my question on this website. What gives? Help.
AnswerTwo questions were sent so I answered the last one. Here is the answer.
The gall is a very common one on cottonwood trees. It's the Poplar Petiole Gall, caused by the Poplar Petiole Gall Aphid, Pemphigus populitransversus. The aphids overwinter as eggs on the cottonwood's leafless twigs. The eggs hatch in the spring as the leaves develop. When the newly hatched nymphs feed on leaf petioles, they cause galls to form and the small, dark-colored aphids move inside. The aphids secrete a white, waxy material which coats their body. After two weeks, the females bear live young that mature into winged females. These females leave the gall and find plants in the mustard family, where they bear more female, mustard-eating aphids. In the fall, winged forms appear on the mustards, and these fly back to the cottonwoods, where a male and female generation is produced, and then one egg is laid by each female somewhere on a cottonwood twigs, that egg overwinters, and the life cycle begins again next spring.
