Insect Explosion Spawns Sticky Situation for Residents This Season

Got tree goo all over your car? Black stickiness on the sidewalk? Did you think it was sap from a nearby camphor tree?

Well, you’d be close—but it turns out that sticky goo comes out of aphids, feasting on those camphor leaves.

There’s been an explosion of the tiny insects, locally, this year, says Albany’s Urban Forester, Tony Wolcott. Same in Berkeley, says Dan Gallagher, Senior Forestry Supervisor, with Berkeley Parks.

They say it’s likely connected to the weather. A warm spring allowed aphids to hatch earlier, and a lack of late rains meant none were washed away. Once the population gets dense enough, the biological controls—birds, insects—can’t keep up.

Aphids suck fluids from green leaves, leaving them curled or yellow, and what the aphids excrete is charmingly called 'honeydew'.

“All this is, is a sugary substance with excess nutrients,” says Gallagher.

The black stickiness you may see on leaves, the sidewalk and street, or your car, is sooty mold fungus that grows on the honeydew.

There are about 150 camphors in Albany and about 1,000 in Berkeley, say the city staffers. Not all trees are affected. Wolcott says he’s had about 10 calls complaining about the goo this year, compared to none last year. Gallagher says Berkeley Parks has gotten a number of calls as well.

Neither city will use pesticides for the aphids, but in Albany staff may trim the most infected branches from the trees.

The honeydew comes off cars and sidewalks with a fairly quick, strong blast from the hose. Gallagher says residents might even try spraying the underside of their trees with water to reduce aphid numbers.

Cold weather will reduce the population in a few months, and rain will wash the black, sticky soot off the sidewalks and streets, Wolcott says. The aphids will not kill the trees, he says, although they could stress them, making them susceptible to other problems.

For more on aphids, Wolcott and Gallagher recommend the UC Davis Integrated Pest Management website. Camphors aren’t the only trees affected by aphids right now, they added.

Albany residents can reach Tony Wolcott at 510-559-4275 or twolcott@Albanyca.org. Berkeley residents can reach Urban Forestry at 510-981-6660 or visit the Berkeley Urban Forestry website.

Have you encountered this problem? Or do you have an urban forestry question dealing with Albany or Berkeley? Let us know in the comments below. 

If there's something in this article you think should be corrected, or if something else is amiss, call editor Emilie Raguso at 510-459-8325 or email her at albany@patch.com.