Aphids threaten spruce trees

Posted: Sunday, May 27, 2001

The army of spruce needle aphids is back and stronger than ever, sucking the life out of trees in Juneau and other parts of Southeast.

"In Sitka an entire island was attacked and literally it killed every tree," said Cooperative Extension Agent Jim Douglas.

Douglas doesn't want the same to happen in Juneau, so he's mustering tree owners to fight back. At a 7 p.m. Tuesday meeting in the Bill Ray Center, residents can learn strategies to counter the aphids from Forest Service entomologist Mark Schultz and pest management technician Elizabeth Cuadra.

"We're really worried about people potentially losing their big spruce trees in their urban landscape," Cuadra said last week. "We have found live spruce needle aphids in the last week in Juneau, so we know they're out there sucking the juice out of trees."

The infestation has already spread through Douglas, downtown Juneau, along the shores of Auke Bay, in certain spots in the Mendenhall Valley and to Lena Point, Douglas said. The aphids are worst along the water and in other temperate areas.

"If we get two or three more years' attack we're going to have a lot of dead trees, particularly down on the waterfront," Douglas said.

The aphids feed on Sitka spruce trees, drinking sap from their needles. The loss of sap slowly kills even 100-foot trees, which eventually turn brown and drop their needles.

Before coming to the meeting, tree owners should check their spruces for brown patches or bare branches. Also look closely at the green needles near the ends of any branches for the aphids themselves. Smaller than rice grains, the dark green aphids usually align themselves with the needles.

Another test is to lay plastic under the tree. If the plastic becomes sticky there are aphids above. Notoriously sloppy eaters, the aphids drip sap down as they slurp it up.

The safest way to treat infected trees is with an acetate pesticide inserted into the trunk. The acetate travels up the tree and to the needles, where the aphids drink it and die. Douglas recommends ACE Caps available at Don Abel Building Supplies and Western Auto. Treating a 100-inch diameter tree would take about 25 ACE Caps and cost $40, Douglas said. On the other hand, he considers a fully grown, landscaping tree worth about $20,000 because of the many years it would take to grow a replacement.

"You can go ahead and plant a new spruce tree, but you and I will never see it in the majesty it has now," Douglas said.

Infected trees should also be fertilized to help them survive the onslaught, Douglas said.

The Forest Service and Cooperative Extension are also studying the aphid to try to understand it and better fight it off. The Forest Service is getting a DNA profile on the aphid, Douglas said.

Douglas warned tree owners of the aphid problem last summer and some people treated their trees over the winter. But Douglas really hoped Juneau would have a harsh winter to kill the aphids off naturally. One of the reasons the aphids are particularly bad is that the area has been through three very mild winters in a row.

Aphids aren't the only garden pest to thrive over the mild winter. Slugs, bugs and plant diseases also will be coming back with renewed force this summer, Douglas said. Usually periodical thaws over the winter in Juneau cause slug and bug eggs to hatch into larva, which are then killed by a cold snap. Last winter there wasn't really a cold snap.

"I was walking just yesterday through my neighbor's grass and the slugs were all over the place," Douglas said last week.

Gardeners should also be on the watch for currant worms and lilac leaf miners. Cooperative Extension can advise gardeners on organic ways to handle the pests. The office has moved to Vintage Park across the street from Carrs.

Kristan Hutchison can be reached at khutchison@juneauempire.com.

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