Jack pine budworm might be the reason you’re seeing brown branches on jack pine trees, according to the Michigan DNR.
Budworm caterpillars feed off needles on jack pine and red pine trees. This leaves trees defoliated and can cause die-back among the crowns of trees.
Clipped and damaged needles turn reddish brown in early July. Over time, rain and wind remove the dead needles, which can give trees a bare, grayish appearance.
What are budworm caterpillars?
The jack pine budworm, also known as Choristoneura pinus, is a native insect.
The budworm population usually booms and then collapses after two to four years. Outbreaks happen every six to 12 years.
The adult moths are reddish-brown with white markings. They lay masses of green eggs on jack pine needles. When the caterpillars hatch they spin cocoons and remain there through winter. They emerge in the spring.
The caterpillars are yellowish-brown and turn reddish-brown with cream-colored spots. They have a black head and grow to about one inch long.
The caterpillars feed on needles for about six weeks. After that, they pupate and emerge as adult moths in six to 10 days.
What are jack pine trees?
Jack pine is a short-lived species. They often reach maturity at 40 to 55 years.
Trees older than 45 that grow on sandy sites and endure stressors, like drought, are most vulnerable to budworm infestation.
Current management practices include harvesting jack pine before they are at risk. Doing so can reduce the jack pine budworm impact and the risk of wildfires.
Jack pine budworm outbreaks
The last large outbreak happened in 2015 and 118,000 acres were defoliated.
In 2022, about 28,000 acres were defoliated during an outbreak. Severe infestations can kill trees or lead to diebacks in the tops of overmature jack pine stands, which can create fuel for wildfires.
“What we’re seeing right now is an outbreak that started in 2022 with infestations in the central and eastern Lower Peninsula and some small pockets in the U.P.,” said Simeon Wright, forest health specialist with the Michigan Department of Natural Resources.