2026 Christmas Tree Scouting Report May 28, 2026

Weather Update

Over the last few days, PA experienced a prolonged stretch of cool, damp, and highly favorable conditions for fungal disease development. Multiple rainfall events moved through the region beginning late last week and continuing through much of the Memorial Day weekend into early this week. Persistent cloud cover, elevated humidity, and extended dew periods kept foliage wet for long durations, particularly in dense Fraser fir, spruce, and arborvitae blocks with limited airflow.

Daytime temperatures generally remained cooler than average, mostly ranging from the upper 50s into the upper 60s, while overnight lows frequently dropped into the 40s and low 50s. These cooler temperatures, combined with repeated moisture events, created ideal environmental conditions for needlecast diseases and opportunistic fungal pathogens to infect newly emerging growth and stressed foliage.

Looking ahead, the next five days appear significantly drier with cooler nighttime temperatures, lower humidity, sunshine, and increased air movement entering the forecast. Highs are expected mostly in the 60s to low 70s with overnight lows dropping into the 40s. While this stretch should help slow active fungal spread and allow foliage to dry more efficiently between dew periods, growers should not become complacent. Existing infections from the recent wet cycle may continue developing over the coming weeks, especially in stressed or dense plantings. The upcoming dry window may provide a valuable opportunity to complete fungicide applications, improve coverage, and scout blocks more thoroughly before the next extended wet period returns.

Pest Information 

Balsam Twig Aphid

Active balsam twig aphids were observed this week in untreated 2-foot Fraser fir. Feeding damage is becoming more noticeable as new growth expands, including curling, twisting, and distorted needles on tender shoots. While some populations may naturally begin declining as shoots harden off, growers should continue closely scouting susceptible Fraser blocks, especially in younger plantings, where pressure can build quickly.

Treatment options are most effective while aphids remain active on tender expanding growth. Products commonly used by growers include pyrethroids, insecticidal soaps, horticultural oils, and systemic materials labeled for conifer aphid management. Coverage is critical, particularly deep into the expanding shoots where aphids are protected. Growers should also continue monitoring beneficial insect activity, including lady beetles and syrphid fly larvae, which are often present in BTA-infested blocks.

Elongated Hemlock Scale 

Settling elongate hemlock scale crawlers were observed this week, signaling an important management window in some blocks. Crawlers remain one of the most vulnerable life stages before protective coverings fully develop. Growers with a history of EHS should continue scouting carefully, focusing on interior foliage and lower branches where populations often establish first. 

Cryptomeria scale

In many scouting areas across the state, including Cumberland County (558 YTD GDD),  Cryptomeria scale eggs are present beneath scale covers in monitored plantings, although crawlers have not yet emerged. Based on current development and weather conditions, crawler emergence may begin in early June. Beneficial parasitoid wasps actively attacking cryptomeria scale were again observed this week. These beneficial insects naturally suppress scale populations by laying eggs within scales, where developing larvae consume the host insect. Preserving beneficial populations may improve long term biological suppression of scale insects. Begin and continue scouting, flag areas and be prepared to spray once crawlers emerge. Based on your pest pressure, your treatment choice will vary.  Movento is a good choice to protect beneficials like a parasitic wasp that lays its eggs inside of Cryptomeria scale. Bifenthrin, Buprofezin, Chlorpyrifos, Dinotefuran, Lambda-cyhalothrin, Malathion, Spirotetramat, Sulfoxaflor are registered for use. 

The most important factor with cryptomeria scale is timing applications to crawler emergence. Once protective wax coverings develop, control becomes significantly more difficult. Double-sided tape, branch tapping, or hand lens scouting can help determine active crawler periods. Good spray coverage deep into dense arborvitae and interior foliage is essential regardless of product choice. Many successful programs rotate oils, IGRs, and systemic materials to improve long-term control while reducing resistance pressure and preserving beneficial insects. Below is a picture by Don deMackiewicz, Pennsylvania Department of Agriculture,  of empty cryptomeria scale after parasitiod wasp emerged from it.

Spider Mites 

Spider mites remain active in several blocks. While recent wet weather may have temporarily slowed population growth in some locations, the transition to warmer, drier weather could favor rapid population increases over the coming weeks. Growers should continue checking interior foliage for stippling, bronzing, fine webbing, and active mites, particularly in stressed trees and historically problematic blocks.

If populations begin increasing, miticide applications may be warranted before hot summer conditions accelerate reproduction. Coverage deep within the canopy is extremely important. Avoid unnecessary pyrethroid applications where possible, as they may flare mite populations by reducing beneficial predators. Rotating miticide modes of action remains important for resistance management.

Bagworms

We do not have any new reports of bagworm activity this week. Bagworm egg hatch typically begins around 600–900 GDD (base 50°F), with peak emergence often occurring closer to 900 GDD depending on local weather patterns and microclimates. Now is a great time to be scouting your plants; hand pick overwintering or early caterpillar sacks. Early hatch may begin soon if warmer temperatures continue. If you have high numbers of hatched egg sacks and/or caterpillars, we would be look around the next two weeks as an ideal time to treat with Bacillus thuringiensis kurstaki, spinosad (e.g. Conserve), or chlorantraniliprole (e.g. Acelepryn), all of which are highly effective on smaller larvae.  The best control window is shortly after hatch when larvae are very small. Once bags enlarge later in summer, control becomes significantly more difficult. 

Needlecast & Fungal Diseases

Disease pressure remains high following the extended wet period across the region. Needlecast and spruce disease applications were completed this past week, along with treatments on arborvitae blocks. Conditions over the last 7 days strongly favored fungal development due to repeated rainfall, prolonged leaf wetness, cool temperatures, and high humidity.

Growers should continue monitoring spruce, Douglas fir, and arborvitae for early symptoms of fungal disease a and needle casts- particularly in dense blocks with poor airflow or a history of disease pressure.

Protective fungicide programs remain critical during extended wet periods. Many growers continue using chlorothalonil products such as Bravo Weather Stik where labeled, along with other fungicides rotated for resistance management and broader disease coverage. Good spray coverage throughout the canopy is essential, especially on interior foliage. The upcoming dry stretch should provide an excellent opportunity to improve coverage and maintain protective intervals before additional wet weather returns.

Green Giant Arborvitae

We do not have any results back from the lab, but more growers are reporting fungal activity on their green giants arborvitae.  Closely inspect for the black fruiting bodies. Most growers that are treating their Douglas Fir with Bravo Weather Stik, have also treated symptomatic arborvitae. We will continue to update on this topic. 

Spotted Lanternfly

First instar spotted lanternfly nymphs were observed this week in SE Counties of PA, signaling the beginning of active hatch in many areas across southeastern and central Pennsylvania. Newly emerged nymphs are very small, black with bright white spots, and are often difficult to notice unless growers are actively scouting field edges, wood lines, and nearby host vegetation.

At this stage, nymphs are highly mobile and may be found feeding on a wide range of plant material before later concentrating on preferred hosts as they mature. While Christmas trees are not considered a primary host crop, growers should remain aware of SLF activity around field borders, hedgerows, tree lines, and adjacent properties, especially where populations have been historically high.

Common host plants and agricultural crops impacted by spotted lanternfly include:

• Tree-of-heaven (preferred host)
• Grapes and vineyards
• Apples and other orchard fruit
• Maple
• Black walnut
• Willow
• Birch
• Hops
• Stone fruit crops
• Various ornamental nursery crops

Young nymphs often feed on tender new growth and herbaceous vegetation early in the season before migrating to woody hosts later in summer. Management at the first instar stage is generally most effective before populations disperse widely. Contact insecticides commonly used for spotted lanternfly suppression include products containing bifenthrin, carbaryl, and other labeled pyrethroid materials. Penn State research has shown strong knockdown with several contact materials, particularly when applications target concentrated populations along field edges, tree-of-heaven, and other preferred hosts. Coverage and timing remain critical, especially while nymphs are small and actively feeding. Growers should always confirm products are labeled for the intended crop and carefully follow pollinator precautions, REIs, and application restrictions.

Next Report

Stay vigilant in scouting and contact Kelly at keg200@psu.edu with any questions or to share observations.  We have been getting more information throughout the state, which has been helpful in sharing a more comprehensive report. We appreciate everyone who takes the time to share what they are seeing in their fields and beyond!

As always, growers should carefully read and follow the most current product label before making any pesticide application. Labels can change; rates may vary by crop or application method, and specific restrictions regarding PPE, reentry intervals, pollinator protection, and seasonal maximums must be followed. The Pennsylvania Department of Agriculture reminds applicators that "the label is the law" and that all pesticide applications must remain in compliance with both federal and state regulations.

The next scouting report will be available on June 3, 2026. Reminder, please submit observations anytime prior to Tuesday, June 2, 2026, by noon to Kelly Piccioni at keg200@psu.edu to be included in the next report. As a reminder, you may also call into the hotline weekly for updates: 1-800-PENN-IPM (1-800-736-6476) option 5.