Attack of the adelgids!

The Eastern White Pine, Pinus strobus, is a fast-growing native used for plantation plantings, screens (where there isn’t too much wind), specimen trees and hedges. Its needles are long, slender and soft, and they eventually cover the ground, making a downy woodland carpet.

The trunks are stately and the branches whorl around it. A mature tree has dark brown-ridged bark, which adds to the appeal of the tree. It is a handsome species, elegant and ornamental in shape, but it also serves as a valuable timber tree.

White Pines are one of the fastest-growing landscape pines, reaching 50-75 feet tall in about 25-40 years. Some consider them invasive species, albeit a native, not exotic one. At my house, they have proven not to be quite as tenacious. I am forever finding and weeding out walnut and red maple seedlings from my garden but I have never seen a self-sowed White Pine seedling. Reportedly, White Pine re-seeds itself so quickly, especially in abandoned fields, that I remember my grandfather calling it "old field pine." 

At my house, we chose Eastern White Pine to fill in and add shade to what was originally pasture land. My husband planted 1,000 small saplings around one edge of the perimeter of the property for privacy when we first built our house. He prefers not to see his neighbors (and our neighbors feel the same way, though not from lack of friendliness. It's rather the hermit mentality we rural dwellers often have). I remember the saplings at knee-height, and now I walk under them in a magical forest that borders our dirt driveway and opens up to the “glen” that encompasses our house. 

In our 21 years of residence on our property, the White Pines have been the glory of the garden, creating a park-like atmosphere and giving me lots of pine needles for mulch. We thinned a few out in the early days, but now they are established and easily reach 50 feet high. Our only real battle with them is Oriental Bittersweet, which has to be cut out of our trees each year.

This year, when everything else in our garden was growing heartily (we finally had some rain), the White Pines started to look, well, white. The trunk of each tree looks like Tom Sawyer conned some of his friends into whitewashing them instead of Aunt Polly’s fence. One side of our driveway glows in the dark from the white, cottony mass on the bark of each tree.

After doing some research, we discovered that the whitewashing was actually the work of the Pine Bark Adelgid — yes, similar to that same adelgid that attacks the hemlocks but this one sticks to pines. It attacks Scotch Pines, Jack Pines, Ponderosa pines and Pitch pines, but mostly focuses on White Pines. 

It turns out it isn’t going to kill my white pines, although if the adelgids had attacked when they were knee-high to me, that would have been a problem. For mature trees the problem is primarily aesthetic.

This "whitewashing" is actually a white, wooly mass that's created by the female to help hide her eggs; she lays about about 24 in each cottony secretion. That means my trees had literally millions of adelgid eggs on them.

Most of these insects over-winter as immature females. As temperatures begin to rise in late winter, the females resume development, and, without mating, each one lays about 24 eggs within her protective woolly secretion.

Then the female dies. The hatchlings, called crawlers, have legs and can move about. A very few of them have wings, and all or almost all of those that are winged are females. The crawlers transform into another stage, called nymphs, and these settle in to feed and develop, which they do rapidly. Soon, they are mature and have 24 or so eggs beneath them, and so it goes. In one season, there are easily five generations. In theory, one over-wintering mom could have about eight million offspring by autumn, according to an article in the winter 2007 issue of Northern Woodlands Magazine.

That is a sobering thought, and one that has me wanting to rush out and buy natural predators, which come in the form of lady beetle larvae, several flies and the tooth-necked beetle. The tooth-necked beetle can exist solely on a diet of wooly adelgids and is gaining some popularity in its ability to help control them naturally.

Adelgids are tiny, sap-sucking insects that are closely related to aphids, and they are often mistaken for them. The insects are about 1/32nd-of-an-inch long, but their mouth parts, called stylets, are 1/16th-of-an-inch long. The mouth parts are used to penetrate the bark and into the phloem, a layer of tissue inside the bark that transports food from the leaves to the roots. With this many adelgids sucking away on my trees it seems impossible that damage can’t be done, but so far, we don’t see any, just as promised. The Pine Bark Adelgid is evidently one of the few gardening problems that will solve itself. It is short-lived and the adelgids will move on. 

That is my kind of gardening problem. Instead of fretting, I can actually marvel at the scene. Just think — something as small as 1/32nd of an inch finds a way to play a part in this bigger picture we call our world. I’m left with the knowledge that, at 5’6” and several pounds (no, I’m not saying), I’ve got nothing on this tiny little adelgid.

— Cinthia Milner gardens in Leicester.

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4 thoughts on “Attack of the adelgids!

  1. Taffymom

    Wow, so that’s what the white ‘stuff’ on my white pines is! Glad to know it’s not deadly, since I have a line of these beautiful trees along my creek bank. Thanks for the good information.

  2. Guard-ener

    OK, Mountain Xpress — THIS IS A GARDENING COLUMN! Funny, well written — and it’s about plants! Please keep them coming. (Not that I mind the sustainable living stuff, but gardeners want gardening!)

  3. Tedsaid

    Appreciate the good info about these pines–was wondering what to do about mine. Especially glad to know it’s not the same as the wooly adelgid that’s causing so much devastation to WNC hemlocks. Maybe a follow-up article on that issue? That would be great!

  4. Jonathan Barnard

    I doubt your black walnut seedlings were self-sown. I expect they were squirrel-sown.

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