Don’t be surprised – scout now for late season Christmas tree pests

Late season pests such as pales weevil, spruce spider mites and spruce-fir loopers can still affect the quality of your Christmas trees before harvest.

With Labor Day just around the corner (September 3), attention often shifts from growing trees to marketing and the harvest ahead. However, growers should continue to scout their Christmas tree fields for late season pests that can still affect the trees quality this fall. Here are a few particular pests to watch for.

Pales weevil

Pales weevil adults emerge now through October from old stumps and root systems. They spend the day in the litter around the trees and move onto trees at night to feed on shoots and twigs. These adults typically feed for two to three weeks before eventually seeking a site to overwinter, usually in litter below the tree. Feeding at this time of the year can cause flagged shoots on Douglas fir, true fir, white and Scotch pine. Look for brown twigs and branches with small, irregular patches of exposed wood on stems or at the base of shoot. Scout 50 random trees for branch flagging. On older trees, if you find an average of five flagged branches, consider treating with a registered insecticide.

Flagging on douglas fir
Flagging on Douglas fir caused by pales weevil. Photo credit: Jill O’Donnell, MSUE

Oval feeding scars
Oval feeding scars on shoots. Photo credit: Jill O’Donnell, MSUE

Spider mites

Spruce spider mite populations may build again this time of the year as temperatures begin to cool. Pay particular attention to the trees you plan to harvest this year. Check for mite activity weekly by closely inspecting the older needles near the tree stem or by sharply rapping shoots over white cardboard or a notebook with white paper. Spruce spider mites will tend to be reddish, green to dark red in color.

Bronzing of fraser fir 
Bronzing of Fraser fir foliage due to spruce spider mite feeding.
Photo credit: Jill O’Donnell, MSUE

Spruce spider mite
Spruce spider mite adult. Photo credit: USDA Forest Service, Bugwood.org
 

Spruce-fir looper

This insect may go unnoticed on Fraser or balsam fir until the trees have a significant amount of damage. The caterpillar is anywhere from 0.25 to 1 inch long, light green with dark green and white stripes. The head capsule is light brown. The larvae chew notches out of the needles, which after a few days turn brown. Needles can also be found hanging from silken threads. Most of the damage can be in the top part of the tree, but feeding can be found throughout the tree. Use a scouting board or a white sheet of paper and tap the trees (like sampling for spider mites) to find these larvae.

View the MSU Extension spruce-fir looper factsheet for more information on this insect.

Spruce fir looper
Spruce-fir looper. Photo credit: Jill O’Donnell, MSUE

Feeding damage
Feeding damage caused by spruce-fir looper. Photo credit: Jill O’Donnell, MSUE

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