Destroy dead pines now to halt wilt disease
The central U.S. pines turning color now could be victims of either drought or pine wilt. In either case, they also could be a kind of time bomb for healthy pine trees.
The reason is a long-horned, cylindrical insect called the pine sawyer beetle. It prefers laying its eggs on stressed or dead pines--including recently cut pine logs. Its newly hatched larvae will overwinter there.
Unfortunately, these sites are also prime spots to find a microscopic worm called the pinewood nematode. Its claim to fame is that it can reproduce so fast during a typical summer that its numbers can literally shut down a pine's circulation system within weeks. The result: deadly pine wilt.
The only way to stop the disease's spread is to break the unique tie between beetle and nematode.
The two don't truly get together until spring. Then a new generation of pine sawyer beetles gears up to fly to find another pine on which to feed. At the last minute, though, up to 100,000 tree-clogging nematodes quickly hitch a ride in each beetles' windpipe.
The nematodes will enter their new host through the feeding holes the beetles create. The symptoms of that death sentence will usually appear by August through December.
Typically, the needles of an infested tree will wilt. The symptoms can appear across all of a tree or in progressive parts. The tree itself will die within a matter of weeks or a few months. The dead needles will hold on for up to a year.
The way to break this cycle is to get rid of the beetles' and nematodes' overwintering sites. Dead pines must be down and gone by May 1--at latest. Even a stump can foster pine wilt's spread. The resulting wood must be chipped, buried or burned, to eliminate any possible haven for the deadly pests.