Christmas Tree Scouting Report: May 29, 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)

Pest Information

It's been a wild week of weather across Pennsylvania. Things started off fairly mild, but by the end of the week, heavy rain and cooler temps arrived and certainly did not feel like Memorial Day weekend! Some spots saw over 2 inches of rain, leaving fields soggy and hard to work in. Highs dropped into the 50s, which definitely slowed things down out there. Now is the time to keep an eye out for white pine weevil damage (wilted leaders), Zimmerman pine moth (pitch at branch whorls), and pine needle scale (look for white, crusty spots on needles). Aphids and adelgids are getting active, and sawflies may be feeding on needles, especially on younger trees. Try to spray during dry and low-to-no wind windows. This next week is calling for more rain and lower temperatures through the weekend, but then a rapid increase in temperatures. Crawlers of the below pests will most likely become active early-mid next week: Scout!

Elongated Hemlock Scale (EHS)

Elongated Hemlock Scale crawlers have emerged in Schuylkill County. These flat, brownish scales hide on the undersides of needles, sucking sap and causing yellow mottling, needle drop, and an overall dull appearance. EHS has overlapping generations and is active year-round in PA, but crawler stages are most treatable in late spring through early summer. They can be found on Fraser, Canaan, and Concolor firs. To scout, tap branches over black paper or use sticky tape to detect crawlers. Remove heavily infested trees, mow between rows, and improve airflow to reduce tree stress and pest pressure. Products like Lambda-cyhalothrin, a non-systemic insecticide, are particularly useful for targeting the crawler stage due to its contact and stomach action. Dinotefuran and imidacloprid offer long-term control by being absorbed into the tree and killing the scales as they feed, since they are systemic insecticides. 

Cryptomeria Scale 

This scale, which resembles an egg, will be found on the undersides of the needles of true firs and occasionally spruces and Douglas fir.  Look for a yellow mottling on the upper surface of the needles near the base of the trees. Growers can scrape off the white scale covers with a fingernail and can view the bright yellow, jelly bean-shaped eggs with a hand lens. These eggs are present in Schuylkill and Berks County. The scale crawlers can be expected to hatch from the eggs within approximately 10-14 days after the eggs are laid. These crawlers are vulnerable to insecticides or horticultural oil before they begin to form their protective covering. When crawlers are observed, growers should begin to apply controls. The accepted treatment schedule for this scale is 2-3 sprays, 1-2 weeks apart. There will be a second generation of this pest in early August. Growers who do not achieve good control for the first generation may need to apply a second round of treatments for the second generation.  Effective insecticides include lambda-cyhalothrin, and bifenthrin, both of which are contact insecticides that work well during crawler activity. For heavier infestations or when crawlers are hard to catch, a systemic like dinotefuran can be applied earlier in the season to be taken up by the tree. Horticultural oil is also useful, especially for light infestations, but should be applied in cooler weather and with good coverage. Rotate products with different modes of action, like pyrethroids and systemics, to help prevent resistance and improve long-term control. 

Pine Needle Scale

Growers who grow Scotch and White pines will also want to be on the watch for nymphs or crawlers of the Pine needle scale to emerge. This armored scale, which can be found on the needles of pines and several other conifer species, feeds on the juices from the needles and causes a chlorotic spotting on the opposite side of the needles.  While this is not always a major pest, it can be more serious on Scotch pine. The red/brown crawlers that will emerge are the stage that is most vulnerable to insecticides. Crawlers have not yet hatched in our scouting areas.  When these crawlers are spotted moving on the needles, growers may want to make two control applications, one week apart.  The second generation of crawlers will emerge sometime in July. If populations are heavy, growers may want to consider treating for the scale at that time as well.

Needle Casts

Needle cast diseases like Rhizosphaera, Swiss needle cast, and Rhabdocline thrive in cool, wet weather like we have been seeing. Prolonged moisture on needles creates ideal conditions for infection, with symptoms like yellowing and needle drop often showing later in the season. Dense spacing and poor airflow make it worse. We have seen large amounts of needle cast disease this season and encourage you to consider a fourth or even fifth application of chlorothalonil. 

Mites

Spruce Spider Mites were still active in surrounding counties. The cool spring weather this year may be extending the feeding time of this "cool season" pest. Growers may want to scout fields that were sprayed earlier in the spring to evaluate whether to apply further control. They will become inactive as late spring temperatures heat up, but may still cause damage before that point.  When scouting for spider mites, place a white paper, or clipboard, underneath a bough showing the stippling damage toward the centers of the twigs and tap a few times.  Use a hand lens to look at the moving specks. The spider mites will be dark red to brown.  Looking for Eriophyid mites is a little harder. Select trees with a rusty discoloration and use the lens to look at the needles for peach-colored, wedge-shaped mites. Control is still possible for both mites.

Other Information

The time for treating Balsam twig aphid has passed for most areas of Pennsylvania.  As soon as bud break happens, the aphids move into the protection of the opening buds and begin feeding on the new needles and causing them to twist.  Next season in early spring, growers should begin scouting for the hatch of overwintering eggs.  The white paper technique mentioned above for spider mites can also be used for aphid monitoring.  

The IPM Hotline is now accessible for Christmas Tree Scouting Information! Dial 1-800-PENN-IPM (736-6476), option  5  (Christmas Trees) to hear the latest update. 

We appreciate the feedback and look forward to more site visits!  Contact Kelly Piccioni at keg200@psu.edu to schedule a site visit to your farm. Visits are scheduled by area to maximize travel time and resources, but we are doing our best to meet the needs of our growers. If you have a programming idea, or other areas needing assistance, please reach out! As always, confirm the product is registered for use on Christmas trees in Pennsylvania, and follow all directions according to the product label.

The next scouting report will be available on June 4, 2025.