A winged, fuzzy sign of fall is upon us | PostIndependent.com

A winged, fuzzy sign of fall is upon us

Woolly aphids often choose autumn to briefly adopt a fuzzy winged form, and this year’s hatch was particularly spectacular, arriving like a second bloom of cottonwood cotton or a plague of fairies.

“There’s a lot of them around this fall,” said Bob Hammon, an entomologist with the Colorado State University extension.

According to Hammon, there are numerous species of woolly aphids, members of the subfamily Eriosomatinae, on the Western Slope. Some are native, others are exotic, and each has its own favorite hosts.

“They’re looking for a very specific species of tree,” Hammon said.

The woolly apple aphid, for instance, spends most of its time on apple and crabapple trees, bearing live larva asexually and attracting minimal notice. When conditions are right, a new generation of flying, sexually reproducing aphids are born and go off in search of elm trees.

Their approach, Hammon explained, is rather hit or miss. They float around, land on a plant, sample it, and move on until they find what they’re looking for.

“They make up for their weak flight and ability to search with numbers,” he said.

In any case, the aphids don’t seem to take much interest in humans, and are harmless unless you inhale one or get one in your eye. Even their impact on their host plants is minimal.

“If you look at the big picture, they’re probably beneficial in some ways,” Hammon said. “They support a lot of beneficial insects and birds.”

Records indicate they’ve been around since at least the turn of the 20th century without causing any real damage. They’re just another sign of fall.

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