Needles on some eastern white pines across much of New England, New York and eastern Canada are turning yellow and brown again, indicating the renewed presence of disease.
Forest health managers are concerned about the amount of damage these fungi can cause to the eastern white pine, an important tree species across the region.
Three fungi appear to be the culprits. They include Mycosphaerella dearnessii, Canavirgella banfieldii and Bifusella linearis.
The infected needles started to change color in May and they are expected to fall off by early July.
Pines typically hold two or more years’ worth of needles. Current year needles appear at the end of the branch. The needle damage caused by the fungi affects last year’s needles, in the middle of the branch. Diseased needles will turn yellowish brown and then fall off, resulting in trees with thin crowns.
“It showed up suddenly over Memorial Day weekend,” said Vermont Forest Health Program Manager Barbara Burns. “It’s widespread. Wherever we find white pine trees, we see evidence of the needle damage.
New Hampshire Forest Health Program Manager Kyle Lombard agreed. “We’ve been getting a few calls about it. It’s another stressor that harms trees. They take on sort of a rusty red haze. So far I’ve seen it everywhere from the lakes region south. We haven’t checked north of there yet.”
“The Forest Service is working with State Departments of Forestry in northern New England to assess the impact of damage on tree growth,” said Isabel Munck, a US Forest Service pathologist.
Dr. Cheryl Smith, UNH Plant Health Specialist and Director of the UNH Plant Diagnostic Lab, said the Lab has been getting phone calls and receiving samples for the last two – three weeks. The majority of the needles have been infected with Mycosphaerella dearnessii, the fungus that causes brown spot needle blight of pines. The needles that are yellowing and falling off this spring were infected last year. All three of the needlecast fungi infect emerging needles during wet weather in the spring.
Fungicides are usually not recommended for management of the needlecast diseases on white pines. If anyone would like confirmation of which needlecast is infecting their pines, they can submit samples to the UNH Plant Diagnostic Lab. There is a $20 fee for the sample diagnosis. Here is a sample submission form.
The summer of 2010 was the first time in recent years that pines in this area showed so much needle damage. The same group of fungi caused that outbreak. A succession of moist springs caused the fungi to be more prevalent in the last few years.
The eastern white pine ranges across much of eastern North America as far south as Georgia.
Adapted from a USDA Forest Service, Northeastern Area State and Private Forestry press release by Glenn Rosenholm.