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Warm Winters bring Unwelcomed Aphids

Posted by Sue Mauger at Apr 06, 2016 08:56 PM |
Spruce trees that survived the bark beetle infestation years ago may now have to face off with the spruce aphid.
Warm Winters bring Unwelcomed Aphids

Spruce aphids are now infesting Kenai Peninsula trees. Photo credit: USDA Forest Service

As our third mild winter in a row brightens into spring in southcentral Alaska, we are seeing a new indicator of our changing climate: spruce aphid. Originally from Europe, spruce aphid has become established along the Pacific west coast infesting spruce trees especially along tidewater areas and other stressed environments. In Alaska, spruce aphid has damaged coastal Sitka spruce stands in Southeast Alaska since the early 1960s. But in 2015, residents of Halibut Cove on the south side of Kachemak Bay noticed spruce trees dropping needles and even some tree death. This is the first confirmation of spruce aphid on the Kenai Peninsula and represents a significant extension of its known distribution. This year, landowners along the Homer bench are finding tiny green aphids on their trees.

A recent report on Forest Health Conditions in Alaska points to our warming winters for this new invader to Cook Inlet.  Warmer winters result in less mortality and therefore increased populations. The first signs of feeding are yellow patches on the needles in the late winter or early spring (February-March). The video below shows spruce trees in China Poot with needle discoloration caused by aphids piercing the tissue and sucking out the juices from the needles.

With bark beetle numbers expected to be high this summer due to recent warm summers and now spruce aphid infestations due to warm winters, the long-term health of our spruce forest in Cook Inlet is tenuous.