Cottonwood trees are a member of the poplar family. These trees grow quickly, but they have shallow roots and are usually short-lived. Cottonwoods are susceptible to a number of different diseases and insect infestations.
Slime flux is also called wetwood. It is caused by a bacterial infection that enters through wounds in the bark. A wet grayish-brown patch of slime forms on the tree. This slime runs down the bark, according to the Utah State University Cooperative Extension, leaving a trail of dry scummy residue and discoloration. The tree usually dies within two years of infection.
Scale insects are not always recognizable as insects. Female and juvenile scales do not have wings, legs or recognizable body parts. These insects suck fluids from plants. They cause serious damage if they occur in large numbers because they excrete a substance called honeydew that leaves a harmful residue on plant growth.
Cottonwood Leaf Beetle
Cottonwood leaf beetles are approximately 1/4 inch long and are pale yellow with black stripes. The larvae are black and have white spots. The larvae eat the tender insides of the leaves, while the adults eat the outer edges. They prefer cottonwood, basket willow and other poplars.