New treatments protect Christmas from ‘Grinch’ grub

Across northern Wisconsin, many of the state’s Christmas tree growers struggle to protect their trees from an insect pest known as the white grub, which lurks in the soil, feeds on tree roots and destroys the crop.

The grub is the industry’s Grinch, causing persistent damage on as many as 30 percent of the state’s 1,100 tree farms. It has been known to destroy 50 acres of newly planted trees — all 50,000 of them — in one fell swoop.

“Where this grub is problematic, oh, it’s not good,” says University of Wisconsin–Madison entomologist Chris Williamson. “It’s the grower’s No. 1 focus.”

Recently, Williamson and graduate student P.J. Liesch developed a number of protection strategies that can save up to 90 percent of the trees in affected areas. The strategies involve chemical treatments that can be applied in practical ways: root sprays, root dips, soil sprays and soil drenches. Williamson is now working to get the word out to growers through UW-Extension and the Wisconsin Department of Agriculture, Trade and Consumer Protection.

“Fifty dollars of protection can save a grower $20,000 (per acre). That’s a great return on investment,” says Williamson, an extension specialist on insect control. “Equally important, however, is to raise awareness among growers — that they should be monitoring and sampling for this pest.”