A major pest almost unique to the Front Range of Colorado: the hawthorn mealybug. We don’t really know why it likes it here so much, but it is far less common in other parts of the country. This insect can do serious damage to the tree, including mortality. It also drips honeydew which attracts yellowjackets and wasps, and causes staining on hard surfaces under the tree. Control of this pest has been difficult and requires yearly pesticide applications on the most susceptible trees. In 2014 I began treating for this pest with a new (bee friendly!) product and have had excellent results; I intend to keep the secret to myself for the time being.
Hawthorns most susceptible to mealybug (most to least):
- ‘Toba’ English hawthorn
- English hawthorn (other)
- Thornless cockspur hawthorn
- Arnold hawthorn
- Black hawthorn
- Russian hawthorn (fairly resistant)
- ‘Cordata’ Washington hawthorn (very resistant)
If you’re planning on planting a new hawthorn tree, I’d suggest going with the Russian or Washington. Again, this is a serious bug and it will kill trees.
Circled in yellow are adult mealybugs feeding along the twigs of a hawthorn. Circled in blue is another pest: hawthorn leafminer.
Pictured here are overwintering adult mealybugs on a hawthorn tree. This is a severe infestation that is jeopardizing the life of the tree.