Christmas tree update – May 26, 2023

Bill Lindberg<lindbe35@msu.edu>, Michigan State University Extension - May 30, 2023

Be prepared for continued warm temperatures and no precipitation. Irrigate trees wherever possible, especially on recently planted fields.

GDD maps of Michigan. — Photo 1. Map of growing degree day accumulation (left) and comparison to normal (right). Photo by MSU Enviroweather.

Weather update

Growing degree day (GDD₅₀) accumulations vary, with over 400 GDD in southern Michigan and around 200 GDD in the Upper Peninsula, indicating heat accumulation for the year is either normal or slightly ahead of schedule by three days, depending on your specific location (Photo 1). For the next two weeks, continued dry weather is forecasted for the entire Great Lakes region. May has been abnormally dry, and soil moisture is rapidly decreasing. At the same time, the amount of water trees require for photosynthesis is increasing due to higher temperatures and expanding tree growth. Despite being significantly earlier than usual, Michigan State University Extension advises growers to assess soil conditions and consider irrigation if feasible. Keep close attention to recently planted trees more prone to drought stress.

Christmas tree development

Depending on your location and tree species (Photo 2), most trees have begun vegetative growth for 2023. This stage of development is prone to fungal infections. Maintain protectant fungicide applications in fields with previous disease issues and on highly susceptible tree species, such as Douglas fir and Colorado blue spruce. Low (no) rainfall should reduce disease pressure, as fungal spores rely on wet needles for infections to initiate.

Christmas tree field. — Photo 2. Differences in budbreak between early (concolor fir, left) and late (Fraser fir, right). Photo by Bill Lindberg MSU Extension.

Insect update

Several growers have reported balsam twig aphid damage (Photo 3). Adult aphids can be found by utilizing a scouting board and a hand lens. Treatment for balsam twig aphid needs to occur before 150 GDDs. The treatment window for balsam twig aphid in 2023 has passed. Keep in mind trees will outgrow some balsam twig aphid damage over the course of the year due to continued needle growth.

Photo 3 balsam twig aphid damage concolor cropped.jpg — Photo 3. Balsam twig aphid damage resulting in twisted needles on concolor fir. Photo by Bill Lindberg MSU Extension.

For management information and upcoming events, sign up to receive MSU Extension’s Christmas tree production newsletter. For general information, visit MSU Extension's Christmas Trees website.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).