Budworms know jack

Some of the lakes area's most abundant neighbors are having a tough summer.

• Photos

Jackpines in north-central Minnesota are suffering from an infestation of jackpine budworms. If the jackpine in your yard is looking a bit dry, with reddish needles and an increasingly bare crown, it could be infested with the worms and it might be too late to save it.

Last year many jackpines around Pequot Lakes and Pine River had the disease. This year it has spread to Brainerd and points south, especially along the Highway 371 bypass and along old Highway 371 in Barrows. Several years ago there were severe outbreaks in the Park Rapids and Bemidji areas, so the disease appears to be heading south.

These brown jackpines along the Highway 371 bypass are infected with jackpine budworm, a disease that could lead to the trees' death. Note the green, healthy red pines next to the diseased trees. How far the disease will spread is unknown at this time.

Jackpine budworms begin as larvae, the immature, wingless feeding stage of an insect. The larval stage lasts about six weeks, from mid-May through June. The larva eats the male cones of the jackpines when the cones are very small, then creates a web on the trees' new needles. Within that web the larva has shelter and food. It cuts each needle off at the stem and eats it, then moves on to other needles. If larvae don't eat all of a needle the remainder turns red. If it eats all of a needle the tree becomes bare. Thus the reddish, bare trees that carry the mark of the jackpine budworm.

After larvae become moths the moths are carried by wind to other trees, where the process starts over. Each tree goes through a two-year cycle of infestation. Severity varies from tree to tree. Some survive, others die. If an infested jackpine in your yard is 45 to 50 years old you might consider harvesting it, said Dean Makey, DNR forester in Brainerd. The DNR harvests infected jackpines on state land and sells the wood to a Potlatch sawmill near Bemidji, where it's sawed into boards. Smaller trees are sold for pulpwood.

Can diseased jackpines be saved?

"Very hard to do," Makey said. "With larger trees you're talking about trying to eradicate thousands of worms. Watering trees is about all you can do. It helps them stay healthier when they're being stressed by insects."

Bt (Bacillus Thuringiensis), a natural soil bacteria found worldwide, will occasionally save a diseased jackpine. When applied it kills the moths and butterflies in their caterpillar stages. When eaten by a caterpillar, Bt causes paralysis and the caterpillar stops feeding and dies.

Don't look for Bt at Fleet Farm, Makey said, for it can only be purchased from commercial applicators. It was used to control forest tent caterpillars around Gull Lake a few years ago.

Makey said he can't predict how widespread the infestation of jackpine budworms will become in the lakes area.

"Maybe the winds will tell," he said. "That's how it moves, so we'll have to wait and see. In my travels I haven't seen it in the eastern part of (Crow Wing County). I'm working on a timber sale in Wadena County and I've seen it there, especially along the Cass County line."

VINCE MEYER can be reached at vince.meyer@brainerddispatch.com or 855-5862