Q: My Hawthorn has white fuzz on the branches. What is this?
– Kelly, Louisville
A: The white fuzz is most likely the adult stage of the female Hawthorn Mealybug. The body of the female is red, but it is covered with a mass of waxy material that looks like fuzz. This covering protects the adult female and her eggs.
These insects pierce the thin bark of small branches and twigs of Hawthorn trees, then suck out the nutrient-rich sap. The insects require nitrogen, but since the concentration of nitrogen in the sap is quite low, the insects need to extract large amounts of sap. The specialized gut of the insect removes the nitrogen and excretes the waste, called honeydew.
The depletion of sap can severely affect overall health and vigor of the tree. Dead twigs and small branches are not uncommon. The honeydew that lands on the leaves can be unsightly, but if the honeydew lands on the branches or trunk, it is usually colonized by sooty mold. Sooty mold is black and detracts from the overall appearance of the tree, especially on varieties with colorful bark.
There are few natural predators of the Hawthorn Mealybug. Chemical controls include a dormant oil spray or a contact insecticide applied in late spring through early summer. Systemic insecticides provide the best control and should be applied in late fall or early spring.
Robert Brudenell is a registered consulting arborist and owner of The Natural Way Inc. Send questions to Robert@thenaturalwayinc.net.
