Woolly Aphids: What's that Fluffy White Stuff on my Tree?
White, Fluffy, Cottony Covering on Tree
If you have discovered a tree with a fluffy, white, cottony looking growth on it it's probably a colony of Woolly Aphids.
Woolly Aphids get their name from the fluffy, wax like substance which covers their bodies and serves as a deterrent to other predators.
At first glance you may mistake them for a fuzzy mold.
What is a Woolly Aphid?
A Woolly Aphid or Erisoma lanigerum is a type of sucking insect that lives on the fluid of plants and trees. Adults are approximately 2 mm in length and are a pinkish brown color. Each adult can produce up to five live young per day. The young Woolly Aphids are green or blue in color. After a few generations winged adults develop to spread to new branches and nearby trees.
A Woolly Aphid Colony up close.
Black Sooty Mold
Close-Up of a Woolly Aphid Colony
From a distance a Woolly Aphid Colony can appear to be a fuzz or moldy growth on the tree branch. The close up picture of the Woolly Aphid colony on the right shows tiny black 'dots' amongst the fuzzy, white, cottony substance. Those dots are the bodies of the Woolly Aphids.
The fluffy looking stuff is the waxy secretions that cling to their bodies. The wax secretions blow in the breeze adding to the appearance of cotton or wool growing on the branch.
Honeydew & Black Sooty Mold
Woolly Aphids secrete a sweet, sticky liquid called honeydew. The honeydew can drip to lower branches, leaves and even the ground.
Honeydew is difficult to remove but otherwise it doesn't cause any real problems. It does however, attract Black Sooty Mold. Sooty molds are a type of fungi that grow on the sugary honeydew secreted by sap sucking insects like aphids. Where there is black sooty mold there is always honeydew.
The picture on the right shows a black, sooty covering on the leaves in the center. The branch directly above the sooty covering was covered with the Woolly Aphids shown in the other two pictures.
How to Get Rid of Woolly Aphids
Having Woolly Aphids is not a major cause for concern. Severe cases are extremely rare and getting rid of a colony of them is fairly simple. The biggest hindrance is to the host plant or tree which may show signs of stunted growth, curling of the leaves, browning or wilting.
The best solution is also the quickest and most inexpensive. It's a garden hose with the nozzle set on full blast. Spraying them will knock them to the ground and they will be unable to return to the host. Do this every few days until you no longer see any signs of them.
Another simple method is spraying them with soapy water and rubbing them off with a brush, rag or sponge.
It is not recommended that you use any type of pesticide on them. Pesticides will do more damage to beneficial insects in your yard or garden than they will to the Woolly Aphids.