Christmas Tree Scouting Report: May 15, 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

This past week brought a stretch of mild to warm temperatures across much of Pennsylvania, with daytime highs ranging from the upper 60s into the low 80s and overnight lows remaining mostly above 50°F. Scattered rainfall events occurred midweek, providing some much-needed soil moisture but also raising humidity levels—creating favorable conditions for certain foliar diseases. With this week filled with mostly rain, scouting and timely treatment, when conditions are favorable is important.  Many regions in southeastern and south-central PA have now accumulated over 350 GDD, putting us firmly into a period of high pest activity. Northern and higher-elevation areas remain slightly behind but are catching up quickly with the recent warmth.

Balsam Twig Aphid

Egg hatch is complete in most areas, and stem mothers have produced the next generation. Feeding nymphs are now moving into new growth. If bud break has occurred and twisting damage is visible, treatment windows are closing fast. Any remaining applications should be made immediately if thresholds are exceeded.

Elongate Hemlock Scale (EHS)

Crawler activity is expected to begin or already underway in the southeast. Now is the optimal time for crawler-stage treatments using systemic insecticides or registered contact products such as insect growth regulators.

White Pine Weevil

Adult activity is winding down. Any untreated leaders showing flagging or wilting should be marked for removal. A good tip for pruning out the damage, and making sure you cut appropriately; feel the leader! It will feel spongey if you have damage.  Keep gently squeezing until the stem feels firm then cut. When you cut the stem, you will see the white worms inside! Make sure you cut below to healthy wood.

Rust Mites

Continued scouting is necessary on Fraser fir and spruce. Off-color or bronzed needles may signal active populations. Consider a miticide application if populations are found on more than 10–15% of sampled twigs and if new growth is at risk.

Rhabdocline & Swiss Needle Cast 

With rainy, humid conditions, now is a critical period for fungicide applications to protect new growth from infection. Growers should be getting ready to, or should have down their third application. If you have a severe case of needle cast, you may need to apply a fourth, or even fifth application of chlorothalonil.

Cryptomeria Scale

Growers in Berks and Schuylkill Counties have seen scale and eggs, but no crawlers yet. As a reminder, Cryptomeria scale typically has two generations per year in Pennsylvania, with crawler emergence occurring in June and August. Monitor crawler activity using sticky cards or tape to determine the optimal timing for insecticide applications. Check the underside of needles on true firs and spruces, especially if you've had scale issues in past seasons. Crawler emergence is expected in the next 7–10 days in warmer regions. Consider removing and destroying small, heavily infested trees that are not marketable, along with heavily infested branches of larger trees to reduce impact. Pesticide recommendations include: Bifenthrin: A pyrethroid insecticide effective against scale crawlers. Apply when crawlers are active. Dinotefuran (Safari): A systemic neonicotinoid that provides control of armored scales. Apply when crawlers are present. Acetamiprid (TriStar): A reduced-risk neonicotinoid effective against scale insects. Apply during crawler emergence. Pyriproxyfen: An insect growth regulator that disrupts scale development. Apply when crawlers are active. Spirotetramat (Movento, Kontos): A systemic insecticide that controls scales by inhibiting lipid biosynthesis. Apply during crawler activity.

General Information

Stink bugs on Douglas Fir were observed and reminded us of Western Conifer Seed Bug on Douglas Fir that will feed on the cones. Although they are more of a nuisance, they can be problematic for seed producers.  For more information, see the Penn State Extension fact sheet Western Conifer Seed Bug.
With increased pest pressure and rapid plant development, weekly scouting is essential. Use a hand lens, paper plate tap tests, sticky traps ,and symptom-based inspections to stay ahead of problems before thresholds are exceeded. Please continue to monitor local forecasts, and don't hesitate to reach out to your local Extension office for support on timing and pesticide options registered for use on Christmas trees in PA.

You can reach Kelly by email: keg200@psu.edu and are welcome to send pictures and observations from your area to contribute to these weekly reports.