From the Field - Crow's Nest Preserve

Fall's Imminent Arrival

The days are getting shorter. It's dark when I get up now, so it's a little harder to leap out of bed. The nights are cooler—the reliable cat now insists on sleeping under the covers; we'll know fall is really here when all three nestle close. But these are still the "easy days," when working outside is a joy: no numb fingers, winter-runny nose, or sleet-stung face. I enjoy the good weather more knowing that it isn't always like this.

We're mostly cleaned up from recent storms and trying to whip the place into shape for fall events: WebWalkers, Spiderlings, a contra dance, preparing a presentation for the Willistown Environmental Stewardship Festival, helping out at East Bradford Day at Stroud Preserve. We also have planned a community hayride and a family program of star stories at Crow's Nest. Please call us for more information, 610-286-7955, or stay tuned to this space.

This is a great time of the year to visit the preserve. The summer wildflowers are hanging on, and there is just a touch of fall color in the trees. We're about a month away from peak foliage, but we're seeing some great reds and oranges in the black gums. And the red maples I girdled (over a year ago!) as part of a wetland restoration are just now turning fall color prematurely, a sign that the girdling is taking effect.

The dogwood sawfly

Each year the redosier dogwood (Cornus sericea) in the yard is host to the caterpillars of the dogwood sawfly (Macremphytus tarsatus). The sawfly is far better known by its distinctive larval caterpillar; the adult is a small wasp-like fly whose picture I couldn't find on a quick search of the internet. The larvae are a real pest on this red-twig dogwood; they can strip all the leaves off in a couple weeks.

The smallest stage of the caterpillar usually goes unnoticed. By the time they are in their second stage they are covered with a waxy white coating that makes them look like, well, bird droppings—likely a good protection from birds. By this time they are eating many of the leaves down to the midvein.

By the third stage they are yellow and black, a pattern that may offer camouflage as they eventually disperse to locate overwintering sites on the forest floor, according to Johnson & Lyon in Insects that Feed on Trees and Shrubs (Cornell University 1991, p. 126).

The authors note that they also overwinter in wood-fiber wallboard and clapboard siding, and that woodpeckers can detect their presence and cause damage in their feeding. Uh oh, I have seen them climbing the stucco walls of the house toward the cedar siding above.

Most years I have controlled some of them with a strong spray from the hose or knocking them off into a coffee can filled with soapy water. The goal of this IPM, or integrated pest management, is to reduce the damage to a tolerable threshold using means with the least harm to the environment.