Tuesday, May 22, 2018

The White Pine Weevil - a New Film

The eastern white pine (Pinus strobus) is the tallest growing tree species in the northeast; in fact, currently, the tallest living thing in New England is a 175-foot white pine growing in northern Massachusetts.

White Pine

In early colonial times, Britain had long been exploiting the European supply of Baltic pine or "Riga fir" (P. sylvestris), from which masts for her warships were fashioned, and the supply was becoming strained. A dependable source of shipmast trees was badly needed, and the newly discovered eastern white pine in the American colonies was just the ticket. This was the tallest conifer species in all of eastern North America. Masts 40 inches in diameter and 120 feet tall (weighing up to 18 tons) could be readily obtained from these soaring, straight trunks.
Arrow-straight white pine

Massive white pines, straight as a sunbeam, were also highly prized by the colonists for the superb timbers and lumber they could provide, their wood being easily worked; it was light, and strong for its weight. The fledgling colonies sorely needed the pines for building materials as much as the British navy did, albeit for different purposes. The original, primeval stands of virgin pine were relentlessly clear cut, beginning along the New England coast, going north and west from there.

Through the 1800's, central New England was rapidly cleared for agricultural land, to the point where only about 20 percent of that area retained any forest cover. Big pines were no more. With the opening of the Ohio valley in the latter part of the nineteenth century, New England farm land was largely abandoned, and reverted to forest. Many fallow fields seeded in with white pine, eventually resulting in the next round of white pine logging in the early twentieth century. And today, white pine lumber is still in high demand.

One of the downsides of large tracts of pine growing in open, abandoned fields  is that the flush of young pines growing in full sun is a boon to an insect known as the white pine weevil (Pissodes strobi). The vigorously growing saplings are highly susceptible to the onslaught of this weevil, and are a vital part of the insect's life cycle. In spring, adult weevils feed on the tissues of the uppermost shoot and terminal buds (last year's growth); that in itself might not do much damage to the shoot or tree. However, the adult females chew pinholes through the tender bark and cambium layer of the shoot and deposit eggs in them. This is where their young will develop and feed, and there may be hundreds of them in one shoot. The larvae will feed in the soft, developing tissues under the supple bark, which kills the terminal shoot; when they mature to adults, they chew their way out.

The white pine weevil

A pine tree, like most conifers, is programmed to grow one trunk, straight up, by elongating the topmost terminal bud (and growing a whorl of side branches at its base), eventually ending the growing season with a new set of terminal buds for next year's growth.

But when that new terminal shoot is damaged or killed, the whorl of side branches below it curve upward to take over the role of upward-growing leader. Problem is, now there are typically two or more trunks instead of one. It's great real estate for the next generation of weevils, but a severe blow to the value of the tree for man's uses.

Multi-trunk white pine - result of weevil damage

If you've ever wondered why some pines are single-stemmed and others are multi-trunked, you now know the original terminal shoot was either killed or broken. If you'd like to see the weevil's life cycle, then you'll want to watch the latest New England Forests film, "The White Pine Weevil". Click the player below (may not be available in email feeds), or it can be found at our Youtube channel (www.youtube.com/c/NewEnglandForests).

Feel free to leave comments on the blog and/or at the Youtube film.

1 comment:

  1. Great film, Ray! I've always been fascinated by these little creatures and the damage they do. Thank you!


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