We at Whatcom Tree Service see cottonwood trees as a thing of beauty – they grow quickly, they are tall and stately, and we know that they are attractive in almost any landscape. However, they are particularly susceptible to certain types of illnesses and pests, so it’s important to know what to look for and how to keep your cottonwood tree safe! When it comes to caring for your trees, be sure to give Whatcom Tree Service a call. We are your tree removal and maintenance professionals for all tree care.

Slime Flux

This disease, a bacterial infection, is named from the slime that oozes out of the bark of a cottonwood tree after it has been infected. The slime, a foamy sort of texture, dries onto the tree and leaves scum behind. So how do cottonwood trees get this infection? Wounds in the bark make it easy for the bacteria to enter, and it can enter in many ways – improper pruning, weed eaters, or even animals clawing at the bark.

The difficulty is, slime flux will target the heartwood of the tree. The bacteria begins to digest the wood, which creates intense pressure within the tree – up to 60 pounds per square inch. Your tree begins to relieve this pressure through small cracks in its bark. Once you see the foam appear, this indicated that the bacteria has begun fermenting the cellulose of the tree. This kills the bark and any other plants it comes in contact with.

Is there a cure for slime flux? Sometimes a cottonwood tree can be saved. An arborist can drill a hole into the site of the infection and drain away the slime, preventing the pressure from cracking the tree bark. However, this is not a cure. When slime flux is caught early, the tree might be able to be saved! But once more than half of the tree trunk is suffering from slime flux, it’s time to look into tree removal.

Aphids, Scale, and Mealybug

These insects feed on plant juices by sucking them and usually infect new growth of the tree. Aphids particularly like to feed off cottonwood trees, especially if there is a local ant population in the tree. These trees will begin dripping liquid that is similar to sap. In order to treat an infestation of aphids, you will need to spray the tree with insecticidal soap and put out ant traps that use boric acid.

Scale and mealybug are much more difficult to get rid of. You can try insecticidal soap, but if that does not help, you may need to call our professionals to remove the infected parts of the tree.


These insects attack cottonwood and elm trees frequently. If you are looking for any signs that you may have a borer infestation, take a close look at the tree’s shoots. If these turn black, shrivel up, and then die, it’s a good indication that there may be an infestation. The borer larvae burrow into the phloem of the tree, which can seriously harm younger cottonwoods.

Leaf Beetles

The cottonwood leaf beetle is only a quarter of an inch long, but this beetle can completely defoliate a cottonwood tree. Both the adults and the larvae feed off of the bottom part of the leaves, which causes the leaves to dry up and die quickly. A beetle infestation can cause long-term problems and kill all the leaves on the tree in a short period of time.

Contact Us

When it comes to caring for a cottonwood tree, we know a lot can go wrong. Be sure to call Bellingham’s trusted tree removal and maintenance professionals at Whatcom Tree Service today to schedule your appointment!