Woolly Aphids in the Garden: Prevention and Removal

Woolly Aphid Prevention Tips

The Spruce / Alison Czinkota

Of all the garden pests we come into contact with, woolly aphids are one of the most common and one of the most striking. They're hard to miss, appearing like new fallen snow in the middle of summer. They look like tiny fuzzy balls of bright white lint or diminutive cotton balls, and despite being so pervasive, they are fairly easy to get rid of. They have a number of folk names that almost sound affectionate: fairy flies, snow bugs, angel flies, fluff bugs, cotton fairies, poodle flies and fluff angels. Indeed, they do look a bit like tiny magical creatures when they take flight, all white and fluffy and delicate. But these annoying little insects, despite seeming cute to some, wear out their welcome pretty quickly.

What Are Woolly Aphids?

These tiny insects are in the Eriosomatinae family. There are specific types of woolly aphids that feed on certain types of plants such as the woolly apple aphid, also known by their scientific name Eriosoma lanigerum; they are also called "American blight" in the UK where they are common on wild and cultivated apple trees. They also feed on the sap of pear trees, hawthorns, ash, elder, oak, and elm trees. Their actual body color is blue or green, but they appear white and fuzzy because of a waxy protective covering resembling cotton or wool they exude, perhaps designed to protect them while they suck sap from tender plants.

How to Identify Woolly Aphids

Normally one sees woolly aphids in two forms: wingless nymphs, who don't fly and who may form large colonies on twigs or branches, and winged adults that can move to suitable locations to lay new eggs. These garden pests can be identified based on their appearance (white fuzzy lint that clings to twigs, buds and leaves), and by the evidence of damage they leave behind. Plants that have woolly aphid damage will have yellow leaves and leaves that curl and get twisted. There may also be formation of galls or cankers, or a black fungal growth that looks like soot. This sooty mold is formed from the sticky substance known as "honeydew" left behind after woolly aphids feed on plant sap,

Where Do Woolly Aphids Live?

Woolly aphids can be found on all sorts of plants and trees. They're often drawn to orchards, vegetable gardens, and ornamental flower gardens. Woolly aphids tend to appear in spring, once temperatures warm up, to allow them flight and migration from their winter hiding spots (usually beneath tree bark).

close up of white woolly aphid, on green branch

Will Hofacker / Flickr / CC BY 2.0

What Problems Do They Cause?

Woolly aphids feed on sap and typically cause only mild damage that is unsightly. This can be detrimental in ornamental gardens, and a disaster in public botanical garden settings where visitors look forward to viewing plant specimens. In vegetable gardens or on fruit plants, woolly aphid damage can affect the size and quality of the crop yield. The sooty mold mentioned above, in addition to being unsightly, can block the photosynthesis process.

Woolly aphids can also spread other plant diseases, such as powdery mildew, which can ruin the appearance of herbaceous perennials during the growing season, and usually necessitates the removal of the affected foliage. In addition to causing damage, the presence of aphids may be an indicator of other problems present in plants. Aphids are completely harmless to humans and animals.

Prevention Tips

Though there are insecticides made to address woolly aphids, the best methods for eradicating and controlling them are to use natural predators, such as ladybugs, lacewings, or hoverflies. Neem oil can also be used, or natural insecticidal soap, and may also be used to spot treatment to help remove them. Damaged branches or foliage should be trimmed and removed.

Woolly aphids can be removed by a strong spray of water from the nozzle of a garden hose. For severe infestations, consider pruning and removing the affected branches.

Removal Tips

Removing woolly aphids by hand may work if there are only a few of them visible. Just use your gloved hand to brush them away, or use a paper towel. But once they begin to multiply, this method can be messy and might not result in total removal. Spot treatment combined with selective pruning is the best way to eradicate woolly aphids and prevent their return.

Article Sources
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  1. https://hortnews.extension.iastate.edu/woolly-aphids