Is your white pine tree dying? Perhaps, but probably not. Let’s take a close look at your tree and see if there’s anything to worry about, or anything you need to do.
Many White Pine trees turn yellow this time of year because of normal “needle drop” on the inside branches. Eastern white pine trees don’t have needles on their inner branches. Each year, last year’s needles turn yellow and fall off, not to be replaced. This year’s new growth at the tips of all the branches still green and lush. The green needles on the tree are all around the outside, and the inner branches are bare from that point on.
You should, however, keep a sharp eye out for some common white pine problems, and fix them as soon as they appear. Here are the “top four” problems you may find:
WHITE PINE WEEVIL attacks the growth leader (the very tip of the trunk at the top) causing it to wilt and turn brown. Eventually the entire top of the tree turns brown and dies. This is caused by pine weevil larvae, which tunnel inside the tender tip of the trunk. Adult pine weevils usually overwinter in leaf litter, appearing on the host tree throughout April to May as they fly or crawl to leaders of host trees. The female chews out a hole and deposits 1-5 eggs. The hole is then sealed with chewed up bark. There may be hundreds of eggs on each leader. Larva hatch out and start to feed under the bark, killing the leader (sometimes called the “candle”) of the previous year. The new growth of the current year starts to grow but soon droops into a crook. The larvae bore into wood to form pupal chambers.
To treat pine weevils you should first cut the dead leader off. Check for tunnels in the cut off end; they will be filled with sawdust but you can see them. Cut the trunk back until no tunnels show, and burn the cut off pieces. You should then treat the tree (and others nearby) with a systemic drench containing imidacloprid, like Bonide’s 12 month Tree & Shrub Drench. This is a concentrate you mix with water and pour around the base of the tree.
BAGWORMS like to nibble on white pines. You can easily spot bagworms by their cone-shaped hanging bags made of chewed needles and bits of twigs. These are the bagworm’s portable homes, and are sometimes mistaken for small pine cones. They should be sprayed, or treated with a 12-month drench, following the label directions.
WOODPECKERS sometimes create little holes arranged in neat rows, on the smooth bark of white pines. They are a sign of Yellow-bellied sapsuckers; woodpeckers that create rows of holes on the trunks of certain trees and often return to the same trees year after year, along with their offspring. Heavy feeding can damage young trees. We discourage them by spraying black tree wound paint into the holes.
WHITE PINE DECLINE causes pale green or off-color limp, drooping needles that later turn brown. The bark may be spongy and may shrivel and ooze sap. Usually the entire tree is affected at once. Trees usually do not recover and death occurs within four weeks. Causes might be a combination of drought, compaction under the tree or disturbance of the root zone. I’ve seen many cases where there is paving close by, causing the tree roots to run out of room as it grows, and leading to drought stress. To prevent white pine decline, avoid machine traffic or digging under the tree, and give your tree a weekly deep-root soaking during drought.
Steve Boehme is a southwest Ohio landscape designer/installer specializing in landscape makeovers. “Let’s Grow” is published weekly; column archives are online at www.goodseedfarm.com. For more information call GoodSeed Farm Landscapes at (937) 587-7021.