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Woodchucks and Squash Vine Borers By Hugh Wiberg

Orginally published in the N.E.P.G.A. Newsletter - March, 1996

It is said that for every creature on this earth there is a purpose. Someday, maybe, someone will explain to me the "purpose" of woodchucks, mosquitoes, black flies, squirrels (the bane of everyone who feeds birds) and squash vine borers.

My pumpkin partner Tom Cone (a biology instructor at Phillips Academy in Andover) and I have been bedeviled by woodchucks the last several years. In 1992 we grew our biggest pumpkin so far, a 582 pounder from a seed sent along by Mike MacDonald of Ontario. In 1993 and 1994 our best plants were severely damaged, in spite of our continuing efforts toward bombing the chuck dens in the area and enclosing the pumpkin patch, (90' by 45') with a sturdy fence. A small percentage of the varmints have always managed to get over, around, or through the fencing.

This year we decided to install a double strand electric wire fence a foot or so inside of our regular fence. This was accomplished for just under a hundred dollars, and utilizes a 6-volt battery instead of an electric plug-in. (Our patch is too far removed from an electrical outlet.) Others who have used electric fences, including the Hackneys and the Chaponis', have had good success with them. The fence delivers enough of an attention getting buzz, without killing the varmint, to encourage the chuck to have his breakfast elsewhere. If this works, Tom and I will no longer have an excuse for not producing pumpkins over 700 pounds.

Our pumpkin growing friends in Nova Scotia (and other parts of Canada) have one distinct advantage over us New Englanders. According to Danny Dill, there are no borers on his maritime island. Serious growers here in the northeast usually start out with the false hope that there won't be squash borers in their neighborhood. And if squash and pumpkins' have not been grown in an area for several years, some growers do escape, for a time at least, from borer damage.

The Massachusetts Department of Agriculture estimates that 25 to 30 percent of the commercial crop of field pumpkins are lost each year due to squash vine borer infestations.

Fortunately, this insect pest can be controlled. Like clockwork, the adult borer moth emerges from the soil here in central New England between the 10th and the 15th of June. The adult moth is about the size of a wasp, a little fatter, and has clear wings. Its body is reddish, and shows a thin line of black dots down the center of the back. The female moth can be seen flying lazily among the leaf stems on hot days between mid-June and through the end of July. They fly slowly enough that you can sometimes swat them down by hand.

I have studied this pest for 25 years and have often seen them resting on the leaves. I have never seen the female lay her tiny black eggs on the leaves themselves, therefore we do not waste time spraying the leaves. I have watched borer moths lay eggs on leaf stems, and occasionally on the vines. If the plants are not sprayed weekly for seven weeks commencing about June 10, the plants are almost certain to suffer later on. The tiny eggs hatch after three or four days, the larva tunnels into the leaf stem or vine and begins eating its way toward the point where the main stem enters the soil. On a hot day around mid-August the whole plant system collapses and your chances of producing a big pumpkin are pretty much passe.

Dusting the plant with Rotenone or Sevin powder is not the way to go, even with a dust pumper. It is almost impossible to cover all of the stems and vines completely with dusts. The only way to go is to use a compressed air tank sprayer. Tom and I have had good luck with Sevin, using one tablespoonful of the insecticide mixed with a gallon of water. We always spray very late into the evening, just before dark, to allow the bees time to return to their hives. Since the maturing male and female flowers are closed tightly at night, the Sevin solution never enters the inside of the flowers. When the flowers open in the morning, the bees and other pollinating insects are not at all inhibited about completing their task.

The six or seven weekly sprayings are easy at first, since the main runner is only four or five feet out by mid-June. By the middle of July the task becomes a chore, with the entire area turning into a green jungle. We stay with it though, being careful to spray the left stems and vines from both sides of the plant to insure complete coverage.

Here in eastern Massachusetts, we have never seen adult moths around the plants before June 10, or after July 28.

Again - resist the temptation to use pesticides before 7:30 in the evening. Sevin and methoxychlor are quite toxic, and will do a number on your pollinating insects if used carelessly. Follow directions on the insecticide container to the letter.

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