The foliage discolors, and eventually the tree dies. Because the larvae feed underground and the adults are active at night, pine root weevils are difficult to detect. Growers don't know the insects are present until the trees start to fade in color, and then there's no way to protect the trees, says Ken Raffa, a UW-Madison entomologist. Christmas tree growers must control pine root weevils before they infest a plantation, or trees cannot be marketed, Raffa says. This forces growers to apply an insecticide on a preventive basis, which increases their costs if they spray areas that don't need treatment.
Growers currently apply the insecticide lindane to control pine root weevils.
Lindane can pose serious problems because it persists so long in the environment. In addition, many Christmas trees are grown on sandy soils, increasing the threat of groundwater contamination. Although pine weevils always pose a potential threat, their populations fluctuate dramatically between seasons and between farms in a given season. Frequently, there is no need to treat trees, says Raffa. Growers then could use pesticides that are less harmful to the environment.