Christmas Tree Scouting Report: April 17, 2025

Weekly newsletter compiled by Kelly Piccioni, Penn State Extension. This week's scouting data contributors: Kelly Piccioni (Penn State Extension), Jim Fogarty (Halabura Tree Farm), Don deMackiewicz, Sarah Pickel, and Cathy Thomas (PA Department of Agriculture).

Pest Information

This past week in southeastern Pennsylvania, temperatures ranged from lows of 28°F to highs near 70°F, with a notable warming trend beginning April 14th. These conditions have accelerated pest activity on Christmas tree farms, although the low night temperatures are keeping activity low. Spruce Spider Mites have been the most active. We have been observing this damage on Fraser Fir on multiple farms throughout our region. 

White Pine Weevil (Pissodes strobi)

Catches remain low in traps in Berks, Dauphin, and Schuylkill Counties. Although White Pine Weevil adults are active, feeding has not been observed yet. Buds have been breaking, and new cones are forming on White Pine across the southeast area of PA. Soil temperatures have reached 50 degrees, but not consistently with falling night temperatures. It is important to look ahead at the weather, and with rising night temperatures, expect soil temperatures to begin to rise, increasing adult activity. Observe the leaders of pines and spruce for feeding damage. Reference last week's report for more information.

Pales Weevil (Hylobius pales)

Flagging on lateral branches of White Pine and Scotch Pine can be caused by Pales Weevil. Bark gnawing will be observed. If you had previous damage from Pales Weevil, removal of stumps or stump drenches with insecticide is promptly recommended as we are within and beyond the GDD range of emergence in most areas. To identify, they are half an inch long, dark, and mottled in comparison to the White Pine Weevil, which will have two white spots.

Eriophyid Mites (Nalepella spp.) 

Growers in Schuylkill and Berks Counties have reported Eriophyid mite activity and Spruce and Fraser Fir throughout the week. Very small spruce are starting to show less than 1% bud break in the area, so it is a good idea to start scouting your own fields and monitoring the various blocks. For scouting tips on Eriophyid mites, Jim Fogarty of Halabura Tree Farms in Orwigsburg, PA, shares to look at the trees showing a dullness at a distance and on the colder sides of the tree. Upon closer inspection, the needles will have a mottled look. At the base of the needle, you are looking for a clear to pale-colored mite about the size of a stomate. Fogarty shares a helpful trick to find them easier: look for the cast skins, a white filament, that stand out easier than the transparent mites. You will need a minimum of a 10x hand lens to see these mites.  

Spruce Spider Mite (Oligonychus ununguis)

Spider Mites have been active on Fraser Fir, Spruce, and Arborvitae, for those of you who also grow other evergreens. In Schuylkill County, growers report 50% hatched in north-facing fields and 75% hatched in southern-facing fields.  For a great resource, see the Penn State Extension factsheet on spruce spider mites. The easiest way to scout for active mites is to place a white piece of paper under the branch and tap the branch to the paper. You will be looking at the paper for little red moving dots, which are the active mites.  Check the plants in several places, as well as the blocks of trees. If you are finding more than 10-15 mites per plant, spray with a registered pesticide. 

General Information

Although very low counts (one per plant) were reported last week for Balsam Twig Aphid, there has not been any increased activity reported in Berks, Schuylkill, or Dauphin County. As buds begin to swell, feeding on firs and spruce is expected to increase.  Cooley and Eastern Spruce Gall Adelgids will be active on Douglas Fir and Spruce. "This species has a complicated life cycle that involves five biological forms of the insect, three of which occur on spruce and two on Douglas-fir. It requires at least two years to complete all five forms on both host plants. This pest can thrive on Douglas-fir alone by continuous reproduction of two forms, with as many as five to six generations produced each year. However, it appears that those forms occurring on spruce cannot continue producing indefinitely and need to find the second host, Douglas-fir, to complete the entire life cycle." (Source: Penn State Extension Cooley spruce gall adelgid). Inspect the base of terminal buds for feeding. Many growers gain good control by treating Adelgid in the fall, mid-September to early October, to manage overwintering females and prevent early spring damage. Rhizophaera has been observed on Blue Spruce as well in our areas. For more information about spruce diseases, see Penn State Extension's factsheet on Spruce Diseases.

The next scouting report will be available April 24, 2025