Christmas Tree Scouting Report: June 17, 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), Rick Geissler (Berks County), Gerrit Strathmeyer II (Adams and York County) Paul Shealer (Schuylkill County)

Pest Information

More wet weather and chilly nights have kept pest activity low, but fungal issues problematic. The switch to hot, dry weather will happen, and happy quickly this weekend. 

Cryptomeria Scale

Cryptomeria scale with active crawlers have been found in York County. In Schuylkill and Berks Counties, crawlers have been observed under the scale coverings, but not active yet. The warm up should push them to be active quickly. Growers should consider spraying if Cryptomeria scale is active on your trees. Buprofezin and Dinotefuran are recommended.

Fletcher Scale

Fletcher scale has been found on Thuja and Hemlock in our scouting areas. Fletcher scale has one generation per year in Pennsylvania and overwinters as immature nymphs on twigs and branches. In late spring, typically May to early June, the nymphs mature into females and begin laying eggs under their soft, dome-shaped covers. These eggs hatch in mid to late June, releasing crawlers that briefly move before settling on needles to feed. This crawler stage is the most effective time to treat, as they are not yet protected by their wax covering. Through the summer, the young scales develop into immatures that will overwinter and restart the cycle the following year. Monitoring for crawlers with sticky tape or close inspection helps time treatments accurately. Buprofezin and Dinotefuran are recommended for treatment. For more information, visit the Penn State Extension's factsheet on Fletcher Scale

Blights

Diplodia Tip Blight and Botrytis Blight have been presenting itself in our scouting areas of Berks, Chester, Montgomery, Schuylkill, Lancaster and York Counties. 

For treating Botrytis blight and Diplodia tip blight on Douglas fir, the type of fungicide used depends on the disease and timing. Botrytis blight, which appears during cool, wet spring conditions, especially after shearing, affects tender new growth and is most common on young trees or transplants; it typically is earlier in the season, but because of the excessive rain, it is possible for it to be active now. Effective fungicides for Botrytis include chlorothalonil products, which act as broad-spectrum protectants when applied before or during extended wet periods. Thiophanate-methyl, found in products is also effective when applied early. Iprodione products offer some curative activity. Copper-based fungicides may offer suppression, but should be used cautiously as they can cause phytotoxicity damage to soft new growth. These treatments are best applied preventively during wet weather or immediately after shearing, with repeat applications during prolonged wet spells.

Diplodia tip blight typically appears in late spring to early summer, especially on older or stressed (drought) Douglas fir. Last season's drought, coupled with winter, really made all Douglas susceptible. Mancozeb products are considered the most reliable for Diplodia and should be applied preventively at budbreak, repeating every 7 to 14 days during wet periods. Chlorothalonil is sometimes used but has shown mixed results on Douglas fir- evident by diplodia appearing on trees treated with chlorothalonil this season. Propiconazole, a systemic fungicide may also help, especially when rotated into a spray program to reduce spore production. Diplodia treatments should be focused on interior canopies, older trees, and areas with poor airflow or a known history of infection. 

Growers can identify signs of Botrytis blight and Diplodia tip blight on Douglas fir even without a microscope by focusing on visible spore structures. Botrytis blight often appears as a soft, grayish-brown fuzzy mold on buds, young needles, or shoot tips, especially after prolonged wet weather or shearing. It may look like fine webbing or dust and tends to cluster on soft, new growth in shaded or crowded areas.

Diplodia tip blight produces small black specks called pycnidia that form at the base of dead needles or on cone scales. These pepper-like spots are usually found on browned, resin-soaked shoot tips, particularly in the lower canopy or interior of the tree where humidity is higher. The black specks may be visible to the naked eye or with a hand lens.

A Pivot from Dimethoate: 

With restrictions on dimethoate, now is a good time for Christmas tree growers to shift toward more sustainable and targeted alternatives like dinotefuran and buprofezin for managing pests such as Cryptomeria scale and more. Dimethoate has been used for its quick knockdown and systemic action, but growing concerns over toxicity to beneficial insects, environmental risks, and tightening regulations are making it a less viable option.

Buprofezin, sold as Talus, and dinotefuran, sold as Safari, are both useful tools for managing pests, though they differ in how they work and when they are best applied.  It is effective against not just scale insects, but also whiteflies, mealybugs, pear psylla, planthoppers, leafhoppers, and other soft-bodied sap feeders. Buprofezin is an insect growth regulator that targets immature stages of scale insects by interfering with their ability to molt. It is most effective when applied during crawler emergence. Because it does not kill on contact, it works slowly and results may take days or even weeks to become visible. Its residual activity is moderate, and it does not affect adult scales. One of the key benefits of buprofezin is that it is relatively gentle on beneficial insects like lady beetles, lacewings, and parasitic wasps, making it a good choice for growers using an integrated pest management approach. It is especially useful when natural predators are already active and contributing to control.

Dinotefuran is a neonicotinoid insecticide with systemic properties, meaning it is absorbed into plant tissue and targets pests that feed on treated plants. It controls scale insects, aphids, adelgids, whiteflies, mealybugs, leafhoppers, and other pests on evergreens and nursery stock. It provides much faster knockdown than buprofezin, particularly when applied as a foliar spray. It is effective on multiple life stages, including crawlers and early adults. When used as a soil drench, dinotefuran can provide longer-lasting protection, sometimes for several weeks or more. However, it can have a stronger negative impact on beneficial insects, especially when sprayed directly. Dinotefuran is best suited for situations with high pest pressure or where immediate control is necessary.

To summarize, buprofezin is a slower, softer option that works well when preserving beneficial insects is a priority. Dinotefuran is a stronger, faster-acting product that is better for severe infestations but carries more risk to non-target insects. Using these two products in rotation can help manage resistance and balance the need for effective control with long-term tree health and sustainability.

Other Pest Updates

Bagworms are hatching now, and early control is most effective while larvae are small. Treatments like Bacillus thuringiensis (Bt) work well on early instars and are safe for beneficials. As larvae grow, use products like spinosad, bifenthrin, or lambda-cyhalothrin. Focus sprays on sunny field edges where infestations usually begin. Looking ahead, growers should plan to place male pheromone traps in August. These traps serve two purposes: they help monitor the timing and intensity of adult male emergence, and they can reduce mating success by capturing males before they locate females in their bags. Since female bagworms remain inside the bag and cannot fly, preventing mating can significantly reduce egg production for the next season.

Aphids on Norway spruce may still be active, especially on soft new growth. If predator insects like lady beetles or lacewings are present, chemical treatment may not be necessary. If aphid numbers are high and causing visible damage, insecticidal soap, or a systemic product like imidacloprid may be applied. Avoid spraying during hot, dry periods to prevent plant injury.

Spider mites often increase with hot, dry weather. Scout by shaking branches over white paper or inspecting undersides of needles. If mites are found above threshold, miticides are recommended. Rotate products with different modes of action and apply with good coverage to dense foliage.

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! Always rotate products by mode of action and confirm they’re labeled for use on Christmas trees in Pennsylvania.

We have a schedule day change for next week. The report will be available on Wednesday, June 25, 2025. The automatic email will still be sent Thursday at 7AM, but you can check the website as early as Wednesday, late afternoon, for the updated report.