2026 Christmas Tree Scouting Report June 11, 2026

Weather Summary

The past week was generally warm and relatively dry across much of Pennsylvania, allowing growing degree day accumulations to advance rapidly. While many areas remained dry, scattered thunderstorms produced highly variable rainfall totals, with some farms receiving beneficial moisture while others saw little precipitation. These warmer conditions have favored continued insect and mite development, including scale crawler emergence and spider mite activity.

Looking ahead, warm temperatures are expected to continue with the potential for additional scattered thunderstorms. Growers should continue monitoring soil moisture and irrigation needs where conditions remain dry. Although disease pressure may be lower than during extended wet periods, localized rainfall events and periods of high humidity may still create favorable conditions for needle cast diseases and opportunistic pathogens in susceptible plantings.

Growing degree day accumulations continue to advance rapidly across Pennsylvania. These accumulations correspond closely with continued elongate hemlock scale crawler activity, the onset of cryptomeria scale crawler emergence, declining spruce spider mite populations, and the start of bagworm hatch in susceptible hosts. Growers should continue to rely on site specific scouting, as pest development may vary considerably between locations despite similar growing degree day accumulations.

Pests

Elongate Hemlock Scale

Elongate hemlock scale remains active throughout many Fraser fir plantings. Eggs, crawlers, settled crawlers, and developing scales continue to be observed simultaneously, creating overlapping life stages. During scouting this week, some crawlers were actively moving while others had already settled and begun producing protective coverings.

Several growers reported successful applications targeting crawler emergence. In treated blocks, newly emerging crawlers were observed dying shortly after leaving beneath the female scale covering, indicating good treatment efficacy. As more crawlers settle and begin developing their protective wax covering, the effectiveness of contact insecticides will gradually decline. Growers should continue scouting closely, as crawler emergence is expected to continue for several more weeks.

Products labeled for crawler suppression include bifenthrin products such as Talstar and Onyx, Safari (dinotefuran), and Movento (spirotetramat). Thorough coverage of needle undersides remains critical for successful management.

Cryptomeria Scale

Cryptomeria scale crawler activity continues to increase across portions of Pennsylvania. Following the first crawler detection on Canaan fir in south-central Pennsylvania during the previous reporting period, crawlers were again observed this week actively migrating from beneath adult female covers. Eggs, newly emerged crawlers, and settled crawlers may all be present simultaneously as hatch progresses.

The crawler stage represents one of the most vulnerable periods in the insect's life cycle and provides the best opportunity for management. Once crawlers settle and begin producing their protective wax covering, they become significantly more difficult to control. Several growers have already initiated management programs targeting crawler emergence, while others continue to monitor crawler activity using direct scouting and double-sided tape placed on infested branches.

Growers should expect crawler emergence to continue over the next several weeks. The extended hatch period often results in overlapping life stages, making continued monitoring important for determining treatment timing and evaluating efficacy. Fir species, particularly Canaan and Fraser fir, should be inspected closely by examining the undersides of needles for crawler movement and newly settled scales.

Products commonly used during crawler emergence include bifenthrin products such as Talstar and Onyx, Distance (pyriproxyfen), Centaur (buprofezin), Safari (dinotefuran), and other labeled materials targeting exposed crawlers. Centaur functions as an insect growth regulator and is particularly effective against immature scale stages by disrupting molting and development. Distance and Centaur are often favored where preservation of beneficial insects is a consideration, while Safari provides systemic activity and bifenthrin products provide contact control of exposed crawlers. Thorough coverage remains critical for success, especially on the lower and interior portions of the canopy where infestations often develop first.

Interestingly, one grower scouting at approximately 760 GDD reported no detectable cryptomeria scale crawler activity, while others observed active crawler migration. This continued variability reinforces the importance of site-specific scouting rather than relying solely on calendar dates or growing degree day accumulations when making management decisions.

Growers should continue monitoring infested blocks using direct scouting or double sided tape placed on branches to detect crawler movement. 

Spruce Spider Mites

Spruce spider mites remain present in many plantings, although populations appear lower than earlier this spring. Active mites, new season eggs, and residual egg populations continue to be observed. While recent weather conditions may have helped suppress some populations, growers should continue monitoring susceptible hosts, particularly as warmer temperatures favor population development.

Predatory mites and other beneficial organisms have also been observed in some locations. Treatment decisions should be based on scouting thresholds and the presence of active populations. Labeled options include Envidor, Avid, Hexygon, and other registered miticides. Rotating modes of action remains important for resistance management.

Eriophyid (Rust) Mites

Low populations of eriophyid mites were observed this week. At current levels, visible damage is unlikely. These mites are commonly present at low densities and often do not warrant treatment unless populations increase substantially. Continued monitoring is recommended, particularly in blocks with a history of rust mite injury.

Fletcher Scale and Arborvitae Leafminer

Fletcher scale was observed on Emerald Green arborvitae this week. Adult female scales contained bright white eggs beneath the scale covering, indicating egg development is underway. Review of 2025 scouting records showed colored eggs and crawler activity at approximately 1,145 GDD, suggesting crawler emergence is still several weeks away in many areas of Pennsylvania. Growers should continue monitoring susceptible plantings and tracking growing degree day accumulations as the season progresses.

Arborvitae leafminer was also found on the same trees. Damage from arborvitae leafminer appears as browned or hollowed foliage, particularly within the interior canopy where larvae feed within leaf tissue. While damage is often cosmetic, repeated infestations can reduce overall plant quality and marketability.

At this time, treatment for Fletcher scale is generally not recommended until crawlers emerge later this season. White eggs indicate that crawler hatch has not yet begun. Monitoring for the transition from white eggs to colored eggs and eventual crawler emergence will help optimize treatment timing.

For Fletcher scale, effective crawler stage options include bifenthrin products such as Talstar and Onyx, Safari (dinotefuran), and Distance (pyriproxyfen). For arborvitae leafminer, products containing spinosad, acephate, or dinotefuran can provide suppression when timed appropriately.

Safari (dinotefuran) is one of the few products that may provide activity against both Fletcher scale and arborvitae leafminer and may be a useful option where both pests occur simultaneously. Treatment timing remains critical, and growers should continue scouting to determine crawler emergence and leafminer activity before making management decisions.

Bagworms

Bagworms have not yet been reported from Pennsylvania Christmas tree scouting locations (Note that the farms we have scouting reports do not have high populations- it is important to scout own blocks). However, early instar bagworms have been observed in neighboring Maryland, and current growing degree day accumulations suggest hatch may already be underway in portions of Pennsylvania.

Bagworm egg hatch is commonly associated with approximately 635 GDD (base 50°F). Several Pennsylvania monitoring locations have now exceeded this threshold, including Berks, Schuylkill, Allegheny, and Lancaster Counties. Growers should begin scouting susceptible hosts immediately, particularly arborvitae, juniper, spruce, cedar, and pine.

Newly hatched larvae are small and often difficult to detect, feeding initially on needles and foliage before constructing the characteristic protective bags. Young larvae are most susceptible to management efforts shortly after hatch.

Bacillus thuringiensis (Bt) products remain one of the preferred options for early season bagworm management due to their selectivity and effectiveness against young larvae. Additional options include spinosad products and labeled pyrethroid insecticides. Applications made after larvae become larger and bags are established are typically less effective.

Growers should anticipate hatch beginning soon and prioritize monitoring susceptible hosts over the next several weeks.

Green Giant Arborvitae Update

Follow up observations were conducted in Green Giant arborvitae plantings previously exhibiting widespread browning and winter injury symptoms. Growers reported that symptoms have remained largely unchanged since late May, with affected trees actively pushing healthy new growth and little progression of damage observed in recent weeks.

Samples submitted to the Penn State Plant Disease Clinic confirmed the presence of Pestalotiopsis needle blight and tip blight. However, the fungus appears to be acting primarily as an opportunistic pathogen colonizing tissue weakened by winter injury and environmental stress rather than serving as the primary cause of decline. The diagnostic report noted evidence of winter injury on affected arborvitae samples, and Cryptomeria samples submitted at the same time also exhibited symptoms consistent with winter injury. These findings further support environmental stress and winter desiccation as primary contributors to the damage observed this spring.

Pestalotiopsis commonly invades weakened or injured tissue and is frequently associated with environmental stress events rather than initiating disease in healthy plants. This observation aligns with reports from other regions where Green Giant arborvitae experienced significant winter injury following periods of environmental stress.

Current field observations suggest many trees are recovering well and producing healthy new growth. A preventive application of Bravo Weather Stik applied in late May appears to have provided favorable results, with little to no additional symptom development observed in most plants. Growers should continue monitoring affected blocks, prune out dead branch tips where practical, and reduce plant stress through proper irrigation and cultural management during periods of extended dryness. While fungicides may help protect healthy tissue, long term recovery will largely depend on plant vigor and the tree's ability to outgrow winter damaged foliage.

General Recommendations

Scale crawler activity remains the primary insect management focus this week, particularly for elongate hemlock scale and cryptomeria scale. Fletcher scale should also be monitored as egg hatch approaches later this season. Continued scouting will be critical for determining treatment timing and efficacy.

Mite populations remain active but generally low, balsam twig aphid pressure continues to be minimal, and bagworm hatch is likely underway in portions of Pennsylvania. Growers managing arborvitae should begin monitoring Fletcher scale development and arborvitae leafminer activity while continuing to track growing degree day accumulations toward anticipated crawler emergence later this summer.

As temperatures increase and scattered thunderstorms continue across the state, growers should maintain fungicide programs where needle cast diseases and opportunistic fungal pathogens are a concern. Regular scouting remains the most valuable tool for protecting tree quality through the remainder of the growing season.

Next Report

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 18, 2026. Reminder, please submit observations anytime prior to Tuesday, June 16 , 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