Christmas tree farm update – May 1, 2026
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EmailSpongy moth treatment widows open along with other key pest and tree developments.
Weather update
Conditions have seen a major shift over the past week. Throughout April, most of Michigan has been in an extremely active weather pattern with multiple rounds of strong to severe storms, abundant rainfall and well above average temperatures. Current growing degree day (GDD) accumulations base 50 degrees Fahrenheit range from 340 GDD in southern Michigan to 50 GDD in northern Michigan; this is about two weeks ahead of normal (Photos 1 and 2).
The current weather pattern will be cooler than normal and below average precipitation. This is expected to continue for the first half of May. We also have seen several nights with frost and freezing events. Depending on severity of low temperatures, these events can damage trees that have broken bud (Photo 3) but are less likely to cause injury to buds that are only swollen (Photo 4). Practically speaking, there is not much that Christmas tree growers can do to avoid late frost damage (outside of not growing early bud breaking species).
Crop development
Tree development will vary greatly based on tree species and location. Cone development is evident in Fraser fir in the Grand Rapids, Michigan, region. Cone removal is a major expense for growers, however frost events may help damage or kill cones.
Spring herbicide applications should have been completed while the trees were still dormant. Growers that have not yet done so should be especially cautious with systemic herbicides (ex. glyphosate) at this time as some buds may be further along in development and would be susceptible to injury. Systemic herbicides move throughout the entire tree and can cause significant damage or death.
Insect update
Spongy moth treatment windows have opened for southern Michigan but remained closed for northern counties (Photo 5). A spray application is a mandatory component of the spongy moth federal quarantine. To provide more information on treatment options, consider reviewing this spongy moth treatment fact sheet.
Recent scouting has shown low levels of spruce spider mite (Photo 6). Michigan State University Extension recommends scouting for mites at biweekly intervals to determine when (or if) population levels warrant treatment. Consider lower treatment thresholds for trees as they near harvest age, while younger trees will have multiple years to recover from damage.
MSU Enviroweather update
For those in Michigan that use MSU Enviroweather, there is now an app available that allows for mobile use and easier weather data access from field settings.
This work is supported by the Crop Protection and Pest Management Program [grant no 2024-70006-43569] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
