Christmas Tree Scouting Report: March 20, 2025

Weekly scouting report compiled by Kelly Piccioni, Penn State Extension, Schuylkill County.
This week's scouting data contributors: Kelly Piccioni, Penn State Extension, Don deMackiewicz, Sarah Pickel and Cathy Thomas (PDA), Jim Fogarty (Schuylkill County). 

Current pests

White Pine Weevils 

Only one weevil has been caught in Bernville, Berks County, PA this week. Once the overnight soil temperatures are consistently over 50 degrees and overnight temperatures above freezing, we can expect more activity. Because the growing degree day totals are well within the point of emergence, white pine weevils could be active and just not showing up in the traps. Soil temps have been recorded this week in Berks County, at ranges between 48-52 degrees. Schuylkill County Is recording temperatures in the high 30s, low 40s, and mid-40s in York County. It is recommended that growers actively look for symptoms of white pine weevil feeding on the leaders in host tree blocks. The preferred hosts are Eastern white pine and Serbian spruce; however, they will also attack Scotch pine and other pines, Colorado blue spruce, Norway spruce, and other spruces, Douglas-fir, and even occasionally true firs. The feeding damage shows up as small (» 1/8 inch) round holes with bubbles of sap covering them. Look at the leaders to find adults. White pine weevils are about ¼ in length and are mottled brown with a pair of rust-colored and white-colored spots at the rear of the abdomen.  

When weevils are found, insecticide applications should be made very soon after. Apply to the top third of the tree or 12-14 inches. Egg laying can occur within a week of emergence. Once eggs are inserted into the leader, they are protected. The larvae will hatch and begin feeding on the vascular tissue of the leader and will eventually girdle and kill the leader. The leaders will take on a wilted or "shepherd's crook" appearance. When these dead leaders are seen, they can be cut down to healthy wood (to where the interior bark is green), removed from the field, and burned. This removes the weevils from the field. 

If weevils are still being caught in traps a week after the first insecticide application was made, growers may want to consider making a second application.  

Adhere to EPA-registered product labels for all pesticides used. Consideration of application timing, rates, and safety precautions are necessary. Early spring applications of pyrethroids, such as bifenthrin or permethrin, can target overwintering adults, with precise timing determined by growing post-spring, systemic insecticides like neonicotinoids (e.g., imidacloprid) may be applied as a soil drench for sustained protection, again with strict adherence to label directions. Late-season monitoring in July and August may necessitate additional pyrethroid applications to manage the remaining adults. Take precautions to prevent runoff or drift and be aware of resistance management practices.  For more information on this pest, see Penn State Extension's factsheet on white pine weevil.

Pales Weevils

Another pest being monitored by the IPM Program team is the Pales weevil. These weevils are larger, measuring about ½ inch, and have a dark, mottled brown appearance.

Their feeding damage is easily recognizable, as they cause flagging of the lateral branches of Eastern white pine and Scotch pine. Closer inspection of the branches reveals bark gnawing, a characteristic sign of Pales weevil activity. To reproduce, Pales weevils lay their eggs in fresh Scotch pine stumps. Preventing further damage involves either removing these stumps or treating them with an insecticide before egg-laying occurs (7-21 GDD).

Eriophyid Mites 

In addition to infesting spruce, these tiny mites can also be found on firs, pines, and hemlocks. Eriophyid mites typically hatch within a range of 7-22 GDD. When scouting for this pest, their very small, round eggs can be seen clustered on the lower portion of the needles, near the twig. The mites themselves are narrow and triangular, roaming along the needles. On spruce, both the eggs and mites appear peach or salmon-colored, while on firs and hemlocks, they are white or translucent. Regardless of the host, hatched eggs will be clear.

If mites are detected on 80% of sampled twigs, growers may want to consider treatment with horticultural oil or an insecticide. (Note: Applying horticultural oil to Colorado blue spruce will cause its blue coloration to fade due to phytotoxicity.) The first application should be made when most eggs have hatched. If mites remain after 1-2 weeks, a second application may be necessary. 

Current Observable Damage

During our field visits over the last two weeks, we have been observing damage to a few key species of Christmas trees. It is important to identify your problem areas early so you can properly treat this season. If you are currently experiencing any issues, please email pictures to Kelly at keg200@psu.edu, or set up a field visit. 

Concolor Fir:

Sudden discoloration and death of Concolor Fir have been observed in several counties. Upon removal, J roots were observed in every sampling. Coupled with the drought, this could be the environmental factor causing it.  We do have samples off to the labs for testing, so please stay tuned for the results and further information.  

Douglas Fir:

Now is the time to see damage from needle cast. We have observed both Rhabdocline and Swiss Needle cast in the fields over the last few weeks. Rhabdocline can be identified with yellow to brown needle discoloration, premature defoliation, and noticeable fungal fruiting bodies on Douglas fir trees, particularly in the lower canopy. Small yellow spots appear on current-year needles, expanding into reddish-brown blotches by spring with a sharp contrast between healthy and infected tissue. Affected needles may drop early.

Check for elongated brown splotches on the upper needle surface and raised areas underneath. Look for swollen, light-tan fungal structures on the underside of symptomatic needles.

Swiss Needle Cast will present with similar symptoms, but a key diagnostic sign is the presence of tiny, black fruiting bodies (pseudothecia) arranged in rows along the underside of needles, emerging from the stomata. These structures may give the needle a rough or speckled appearance.

Douglas Fir Needle Midge traps will also be placed soon and monitored for proper detection of active adults.  

To learn more about IPM and scouting in your own fields, please consider purchasing the Integrated Pest Management for Christmas Tree Production Guide.

The next scouting report will be available on Thursday, March 27, 2025.