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Spruce aphids have crimson eyes, green six-legged bodies and their populations are booming in Sitka this summer.
Patrick Heuer is Sitka’s resident Forest Service silviculturist –or forest growth expert—and says locals are starting to see the impact of the aphids’ voracious appetite.
“Well around town in the last few weeks we’ve seen a lot of the spruce trees especially the ones near the beach and at lower elevations we’ve had a lot of folks calling in and asking about that. It’s basically the spruce aphids feeding on the needles, sucking the juice out of the needles in early winter/ late spring.”
The result is less than pretty.
“Mid June or so the needles basically turn brown and die and fall off, and that’s what we’re seeing right now. It’s the result of aphids feeding, probably January, February, March, and in years where we have mild winters the aphid population rends to build up so that we get more defoliation.”
Colder winters says Heuer, usually mitigate large aphid populations by killing off their eggs before they hatch. But as warming weather patterns move in, aphid populations move up.
“It’s a sap sucking, insect, so you can think of it as a tree mosquito.”
That’s Ann Lynch, a research entomologist with the Forest and Woodland Ecosystems Science Program. She’s based in Arizona, but has worked the last 10 years studying and consulting on aphid populations in South East Alaska. She says this “tree mosquito” sucks the fluid out of older needles, dehydrating, and literally starving the tree of nutrients.
Normally she says, one warm winter or spring can’t kill a spruce tree, but a few warm winters and springs in a row can wreak havoc on spruce populations—the largest defoliation recorded from these aphids occurred in South East Alaska and totaled around 46,000 acres in 1998.
“There has been an increase in the frequency and severity and extent of spruce aphid outbreaks in South East Alaska, by extent I mean the outbreaks have gone further inland then they did gone in the past. And that does appear to be related to winter and spring temperatures.”
Lynch and Heuer say the best way to know if your spruce has been affected is to look at the needles. What you’d see is the green tips at the end of the tree basically untouched and the inner or older needles in the tree, brown, sucked dry and maybe scattered around the base of the tree.
Heuer says so far this season only trees at lower elevations have been affected, and if you want to protect your tree from aphids there are a few options.
If you already see the aphids you can rinse them off your tree with a hole, or early in the season you can rinse your tree with a soap and water solution to prevent them from attacking. Either way, Heuer says acting early is the best way to protect your garden spruce.
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