Christmas Tree Scouting Report: May 8, 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 

We finally got rain in most of our region, although we are still not out of drought warnings in most counties.  Schuylkill County has been downgraded to drought watch. To check drought status, visit Drought Information.

We know that severe storms ripped through many areas and hope everyone fared okay. With Mother's Day approaching this week, we are starting to see the emergence of almost everything! Although the day can vary on the calendar, Mother's Day has always been a gardener's guide to be safe from frost and a reference for pest activity. Here's hoping for no late frosts and plentiful rain! We have been getting a few questions from growers with expanded nursery inventory, so you may see some pests on the reports that might not be Christmas tree specific, but very likely produced by growers that are Christmas tree growers.

Balsam Twig Aphid

In York County, it has been observed that the second generation of Balsam twig aphid is causing some twisting of expanding needles. The balsam twig aphid has a complex life cycle involving multiple generations. In early spring, overwintering eggs hatch into wingless females known as stem mothers. These stem mothers feed on last season's needles and, as buds begin to swell, give birth to the second generation of nymphs. These nymphs migrate into the opening buds and feed on the newly expanding needles. This feeding causes the needles to curl and twist, leading to permanent deformation that reduces the tree's aesthetic value and marketability. Incorporate cultural practices such as maintaining tree vigor through proper fertilization. Encourage natural predators like lady beetles and lacewings to help control aphid populations. Bifenthrin, Lambda, and Imidacloprid are some options for control, but only reduce the current population and honeydew accumulation, not reverse needle curling.

Spider Mites

New spruce spider mite eggs (Oligonychus ununguis) have been observed in York County.  Damage is identified by needle discoloration due to tissue cell contents, including green chlorophyll, being sucked out by the mites. Last year's growth damage is very visible behind the new growth that is still green and not yet damaged.

If you are considering adding a miticide to your next treatment of chlorothalonil, be sure to check labels for compatibility. Do Not mix horticultural oils, neem-based products or petroleum-based products with chlorothalonil, as it will cause foliar burning, especially as the temperatures increase. Bifenazate is a good knockdown with residual control and low impact on predators. 

Needle Casts

Growers should be applying their second application of chlorothalonil this week to control needle casts. We are still seeing high percentages of damage from Swiss Needle Cast and Rhabdocline Needle Cast in the areas we are scouting. Propiconazole is recommended for Rhizosphaera, but not as strong on Swiss Needle Cast. If you are looking to rotate another product for chlorothalonil, Azoxystrobin and Fludioxonil (expensive) are recommended, but not to be used solely. Chlorothalonil is still the gold standard for control. Trees in Southeastern Pennsylvania are at 100% bud break and have several inches of new growth at this point. We have had several days of welcomed rain, and temperatures are rising; the perfect environment for needle cast to sporulate, so be timely with applications for maximum control. The needle cast diseases of spruce, Rhizosphaera and Stigmina, will also be ready to release spores to infect the newly emerging buds. Rhizosphaera affects Colorado blue spruce and Engelmann spruce, and Stigmina infects Colorado blue spruce, black spruce, and Serbian spruce. The signifying symptoms of these diseases are brown or discolored needles on the lower branches, which exhibit tiny, black fruiting bodies pushed out through the stomates on the undersides of the needles. Growers dealing with rust should begin fungicide applications to the spruce foliage when the new buds have begun to break. Additional applications can be made weekly and should continue until the new needles harden off or the old infected needles are cast. This should also be followed if both rust and needle cast diseases are present. The recommendations for needle cast suggest a 2–3 week interval between applications, although if the season is rainy, that interval can be shortened.

Cryptomeria Scale

No crawlers have been found in our scouting areas yet. As a reminder, in Pennsylvania, two generations of Cryptomeria scale occur. The first generation will emerge at 400–500 GDD (May-June) typically. The second generation will emerge late July to early August. Crawlers will be bright yellow, flat and oval-shaped and will be moving on the needles around the white and yellow adult scales. Growers should be scouting for scales on the undersides of yellow speckled needles found on the lower branches of host trees. An easy way to scout is to tap infested foliage over black paper or a plate to spot yellow crawlers. True firs, such as Fraser, Canaan, and Concolor, seem to be the preferred hosts, but if the pressure is high, Cryptomeria can be found on both Douglas-fir and spruce trees. When the scale crawlers do emerge, growers should be prepared to make at least two applications of an insecticide, 7–10 days apart, to get control of this pest. 

Pine Needle Scale

This week, pine needle scale crawlers were not found moving yet, but the female scale covers have been observed. As the eggs will continue to hatch and the crawlers will continue to move out from under the adult coverings to spread out along the needles. These crawlers will also move to new areas of the tree limbs. This scale can be identified by the bright white, oblong female scale covers. Scale crawlers are flat, oval-shaped shaped and paprika colored. Hosts of this pest include Eastern white pine, Scotch pine, and Mugo pine. Populations are often heavier on Scotch and Mugo pines. It may also be found on spruce, true fir, and Douglas-fir, although these occurrences are less common. Crawler emergence can last 2 to 3 weeks, so if the population is heavy enough to warrant a treatment, growers may want to consider making one application of an insecticide, followed by a second application one week later. If control is not achieved at this point in the season, there is a second generation that is active in mid-July. This is another time when the scale may be managed. If you have already applied Imidacloprid, Lambda, or Dinotefuran, you should see systemic control for this pest. Use Bifenthrin for a knockdown.

Elongated Hemlock Scale 

No Eggs or crawlers were found inside the casings of female elongate hemlock scales this week in our scouting areas. Very soon, these crawlers will be seen moving around on the needles. Look for the scales on the lower branches of hemlocks, true firs, and Douglas-fir (occasionally spruce). The upper surface of infested needles will have a yellowed speckling, and the scales will be found on the underside of these needles. Female scales are oblong, smooth, and amber-brown in color. Male scales are white, shorter, and can have a build-up of waxy filaments. This waxy build-up may also lead to a waxy coating on the upper surface of the infested needles, giving the branches a flocked appearance. The crawlers, or first generation of nymphs, which will soon be found moving among the adult scales will be tiny, oval, and lemon yellow. The scale activity observed this week is a little earlier this year than is usual. Crawlers are normally seen mid to late May. Growers should be scouting populations of this scale now. The crawler emergence signals the time for beginning control applications. There are a few options for elongate hemlock scale control. The standard control application recommended by Penn State research is either a series of 3 applications with 4 weeks between each application, or 4 applications with 3 weeks between each application - Bifenthrin, Lambda, Imidacloprid, Dinotefuran. Some growers have found that a single application of the chemical spirotetramat (Movento, Kontos) has been effective and also controls Hemlock Wooley Adelgid. 

Cedar Apple Rust 

Cedar apple rust is a disease that is very noticeable at this time. As the name suggests, this is a disease that affects two alternating hosts: apple and eastern red cedar. While eastern red cedar is not a Christmas tree, many conifer growers may also be growing this conifer species for the landscape. During this wet, spring weather, galls growing on twigs of red cedar have swollen and produced bright orange spore-producing telia, or tubular growths. The spores released from these growths can only infect apple or crabapple leaves. After the telia are done sporulating, they will dry up and die, killing the twig from the gall to the tip of the twig. Fungal spots develop on apple leaves, which will produce a different spore-producing structure (aecia) on the undersides of the leaves. Spores released from the apples can infect the cedar from mid-summer to early fall. With that infection, a gall will begin to form the following spring, but will not be mature enough to release spores for another year. For management, galls can be clipped off the tree before the telia begin to elongate to stop the cycle. If trees grown next to an orchard regularly have an issue with this disease, a fungicide program for either the apples or the cedar could be looked into.

General Information

Spotted Lanternfly nymphs have hatched in most of our viewing areas. Although Christmas trees are not a preferred host, SLF can feed and lay eggs on several conifers, especially young or stressed trees, and may be a nuisance. If you are spraying for anything listed above, especially with dinotefuran, you will also be controlling SLF at this nymph stage. For all things SLF, visit Spotted Lanternfly Management Resources. 

Coning – If growers were using herbicide to control cones, your window has closed as new growth has emerged and you will cause severe damage and possible death to your trees. It appears to be, as expected with the severe drought, a heavy cone year. Picking the cones off Fraser Fir is highly recommended for proper growth and overall appearance of your trees. Removing the cones in May to June is ideal as it has the least impact for damage, but more importantly, redirects the energy into producing lateral branches and leader growth. Without removal, you will have crooked leaders, weak branching, and a host location for pests, like bark beetles, to thrive.

Please keep sending pictures and observations to Kelly Piccioni at keg200@psu.edu.  We are working on scheduling our farm visits so they coordinate by location as best we can to maximize our travel days. If you and neighboring farms would like to schedule a visit, please email us and we look forward to seeing you! 

The next scouting report will be available May 15, 2025