MSU Extension in Roosevelt County
Sappy Trees Causing Inconvenience
There have been reports of excessive “honeydew” from trees in the area. Honeydew is the sticky sap that falls under trees, usually onto pavement, grass, vehicles and ornamental plants. This inconvenience is caused by aphids. You will be able to find the aphids by looking for tiny pear-shaped insects on the underside of the leaf. They are very small, about the size of a poppy seed or some of the larger species are the size of a sesame seed. They range in color from light green to nearly black. They have many generations per year so populations increase rapidly. Some generations of aphids will develop wings to travel to their next location.
Each aphid species will attack a specific species of plant and will not attack other species. For example, Elm tree aphids will not attack garden crops. Damage caused by aphids is seldom fatal to a tree because trees produce more leaf area than they need, but in the case of our trees, can make a sticky inconvenient mess.
You may have also noticed a few more ants around the sappy tree. The ants protect the aphids from their natural enemies and in turn eat the honeydew produced by the aphids. Placing a barrier around the plant or tree such as a sticky material like Tanglefoot, can keep ants out of trees and shrubs, allowing beneficial insects to attack the aphids.
Montana State University comments “Aphids damage a tree from the leaves out and will not permanently damage the tree. Hosing the tree with a strong stream of water will help. Using horticulture soaps and oils, excluding ants and using chemicals containing pyrethrins are also additional least toxic controls. Lady Bird beetles should be allowed because they are a natural control of the aphid. Remember all trees produce a lot more leaf area than they need to survive so some damage is more acceptable than chemical control.”
For more information on aphids or other insect problems, visit http://scarab.msu.montana.edu/extension/ or call the Roosevelt County Extension Office at 787-5312.
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