Christmas Tree Scouting Report: June 12, 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 Sheeler (Schuylkill County)

Pest Information

Temperatures over the week hovered between Mid 60s to Low 80s°F, with nighttime lows around 50–60°F. Periods of warm and humid weather prevailed, ideal for fungal diseases, and rain provides moisture for spore germination and crawler development.

Diplodia Tip Blight 

Scouters in all of our areas have been seeing small patches of Diplodia Tip Blight. On Douglas fir, look for wilted or brown shoot tips with resin-soaked needles, especially in the lower canopy. Tiny black fungal fruiting bodies (pycnidia) may be found at the base of dead needles or on cone scales. Focus on browning shoot tips, especially in older or stressed trees. The scouting team has seen it in trees 5 feet and larger in areas such as: the middle rows where spray penetration may not be as thorough, along fence rows and tree lines, and older (10 feet +) stands. Use sanitary pruning techniques to remove infected shoots during dry weather, disinfect tools between cuts, and burn or destroy all infected material to prevent further spread. For chemical control, apply mancozeb. Chlorothalonil may not be consistently effective, as shown by its appearance on trees treated several times. With a sporadic presence, some growers are choosing to continue to monitor, but not treat. Larger outbreaks, application of mancozeb is recommended. 

Aphids 

Over the past few weeks, Don deMackiewicz of the Pennsylvania Department of Agriculture has been keeping the scouting up to date on aphids on Norway spruce. Until this week, we have not seen a strong presence in Berks and Schuylkill Counties. A heavier infestation is found on trees with softer new growth than on the trees that have begun to harden off. Aphids like the newer growth because of the "active" nitrogen and fewer chemical defenses. Aphids were also present on Serbian spruce with fleshier growth.  Although a nuisance, they do not appear to be causing damage at this time. Don also found the presence of a beneficial predator, the ladybird pupa, which feeds heavily on aphids. It is not recommended at this time to apply any chemical controls, especially to protect these beneficials and plants will soon harden off and be sheared. We have insect samples submitted for testing and will continue monitoring for lasting impacts. 

Cryptomeria Scale 

No active crawlers have been observed in our scouting areas this week. This weather has kept their activity slow, but many growers do plan on treating next week. It is anticipated they will be active within this next week's timeframe. Scout in areas where you've had issues before, as this pest often re-establishes in the same locations. Check the middle of the block, where spray coverage may not be as thorough. Peak crawler activity occurs through June and again in the second generation, late July through August. During these times, wrap black electrical tape sticky side out, around branches to catch crawlers, look for tiny, moving yellow specks. For chemical control, crawler stages are the best timing for treatment. Recommended products include dinotefuran, acetamiprid, or buprofezin. As mentioned last week, Paul Sheeler, Schuylkill County, recommends spraying systemics during the night to maximize the absorption of the product. When spraying during the day, it will dry quicker, and you may not get the desired efficacy.

Elongated Hemlock Scale 

Although scouters are still finding some live elongated hemlock scale crawlers, they are beginning to get armored and therefore not susceptible to many insecticides. The window is closing quickly for treatment to be effective. Scouting should focus on the undersides of older needles, especially in the lower and interior branches, where humidity is higher and sprays may not reach well. Look for yellow stippling on the tops of needles and the presence of scale covers or live crawlers. Effective control requires multiple, well-timed treatments targeting the crawler stage. Recommended products include horticultural oil (1–2%), dinotefuran, buprofezin, or pyriproxyfen. Systemics are often more effective for high-pressure sites. Rotate products by mode of action and ensure good spray coverage, especially on needle undersides.

Other Pest Information: 

Bagworms will soon be emerging and feeding. Look for small, moving bags on branch tips, especially on sunny, exposed edges of fields. Old bags from last year can be removed by hand during winter to reduce eggs. For control, treat soon after hatch with Bt for young larvae early in the season, or spinosad, diflubenzuron, bifenthrin, or lambda-cyhalothrin for larger ones and later in the season. Mites may still be problematic as the temperatures remain low. Some growers are reporting repeated applications for control. Poison Hemlock will seed soon. If present in your fields, it is time to control it to prevent spreading.  

Beneficial Insects

This week, several helpful insects are active in Pennsylvania Christmas tree fields. Ladybugs and their larvae are feeding on remaining aphids, such as white pine and balsam twig aphids. Lacewing larvae are also present and feeding on aphids, scale crawlers, and young mites. Predatory mites are starting to show up in response to early spider mite activity, especially in shaded areas. Hoverflies and minute pirate bugs may be seen near flowering weeds and will also feed on small pests like scale crawlers. Tiny parasitic wasps are beginning to target Cryptomeria and elongate hemlock scale by laying eggs inside the scale covers. These beneficials may not give quick results but help with long-term pest control and can reduce the need for spraying.

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.

The next scouting report will be available June 18, 2025