Woolly Aphids: What's That Fuzzy Fluffy White Stuff on My 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's That Fuzzy Stuff on My Tree?
From a distance, a woolly aphid colony can appear to be a fuzz or moldy growth on a tree branch. Looking at a woolly aphid colony from above, you see 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 the aphids' bodies. The wax secretions blow in the wind, adding to the cottony or wool-like appearance.
Are Woolly Aphids Bad for Trees?
Aphids, when in small numbers, do little damage to a tree. However, under favourable conditions, the aphid population can grow rapidly and cause serious damage to the tree during the growing season. Aphids attack trees by sucking the sap out of the leaves.
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 pinkish brown in color. Each adult woolly aphid can produce up to five 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. They spread quickly, if not properly managed.
What Does a Woolly Aphid Eat?
Woolly aphids feed by inserting their needle-like mouth into plant tissue. This allows them to withdraw sap. They can feed on leaves, buds, bark, and even roots. As a result of feeding on sap, woolly aphids produce a sticky substance known as honeydew. This can lead to sooty mold on the plant.
Where Do Woolly Aphids Live?
Woolly aphids live all along the Northern Hemisphere. They are prevalent in states such as Vermont. That said, there are numerous species of aphids found throughout North America. These garden pests are usually most active in the springtime and decrease with a rise in temperatures.
What Is That Sticky Black Stuff Dripping From the Trees?
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. However, it does 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 below 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.
Are Woolly Aphids Dangerous to People?
Some species of aphids have been reported to bite people in nature, especially species of large aphids. In general, this is quite rare. People who work with aphids in labs say that they often get bit, but they handle these insects very frequently. While it is not very common, it can happen. Nevertheless, the bite effects are not harmful. Furthermore, no known disease or parasite is transferred from aphids to humans.
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 for removing woolly aphids is to set your hose nozzle 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.
You can also spray them with soapy water and rub them off with a brush, rag, or sponge. It is not recommended that you use any type of pesticide on them because pesticides will do more damage to beneficial insects in your yard or garden than they will to the woolly aphids. Products containing Pyrethroids and Pyrethrin are effective on Apple woolly aphids.
How to Prevent Aphids
- Regularly check plants for signs of infestation.
- Encourage natural enemies like ladybirds, hoverflies, and lacewings to become established in the garden. Plant daisy-like flowers, yellow flowers, and the plant Limnanthes douglasii.
- Avoid using broad-spectrum insecticides. These will kill beneficial insects (as well as aphids).
- Encourage insect-eating birds such as blue tits. Hang feeders in winter and hang nest boxes in spring.
- If you plant new apple trees, use rootstocks. Rootstocks are resistant to apple woolly aphids.
How Did I Get Aphids?
There are two ways aphids can get onto your indoor plants.
- There were eggs already on your plant when it was purchased.
- They flew in from the outside through an open window or door.
What Will Eat Aphids?
Lacewing larvae eat aphids and other small insects. They seize them with their curved jaws. They are up to 8mm long with tapered rear ends. They place sucked-out aphid skins among the bristles on their upper surface to camouflage themselves.
Are There Cheap Remedies for Aphids?
Soap and water can be used to kill aphids. The basic nature of household detergents makes them perfect for getting rid of mild aphid infestations. Dilute a few tablespoons of dish soap in a small bucket of lukewarm water, use a sponge or spray bottle to apply the mixture to the plants where aphids have taken hold.
Organic Remedies for Getting Rid of Woolly Aphids
- Check tree shoots and bark regularly for signs of woolly aphids.
- Scrub areas within easy reach with a brush and a bucket of soapy water.
- Spray infested areas with a firm jet of water to help reduce aphid numbers.
- Spray with natural fatty acids such as an insecticidal soap.
- The parasitic wasp Aphelinus mali will attack aphids above ground level.
- Aphid predators such as ladybirds, aphidoletes, hoverflies, and lacewing larvae can be encouraged by growing flowers which attract them.
Will Killing Aphids Ruin or Save My Garden?
While aphids play a major role in ecosystems, aphids will do harm to your garden. That said, It's important to use natural aphid killer for plants. While aphids are a nuisance, they also attract beneficial insects to your garden such as lady beetles and lacewings. Getting rid of aphids naturally can help protect the insects you want to keep around.
Aphid Genus and Where They Live
About 24 species in North America, Europe and eastern Asia.
There are about 500 species on a great variety of hosts all over the world.
About 4 species worldwide. They are of east Asian Origin.
Three European species and a few East Asian Species
A genus of 50 species found mainly in the Palearctic.
It is widely distributed in Europe and has been introduced to North America.
A genus of about 80 species worldwide
ENTOMOLOGY at the University of Kentucky, "Woolly Apple Aphid".
Good Housekeeping, "The 10 Most Destructive Garden Insects and How to Get Rid of Them"
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
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© 2012 Christine Miranda