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Gypsy moths coming?


Infestation levels appear lower than last year



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June 09, 2010 | 08:57 AM
It can't be seen from the road, but a pink ribbon hanging off a tree branch shows where an adult gypsy moth trap has been set.

The bright green trap that looks like a milk carton is hidden. It hangs in the brush and for the time being, it is empty.

But, local and state officials expect the trap boxes to be full of gypsy moths at some point in July as they try to survey the population in an effort to slow the spread of the invasive pest.

Trappers began setting the boxes in late May. Nearly 29,700 traps are expected to be set in 45 western and central counties in Wisconsin by early July. There are 56 traps set in Walworth County. Bayfield County has the most traps with 1,762, while Walworth is among the lowest. Only 17 traps are being set in Marinette County.

"Trapping tells us where the moths are and where they're not," said Chris Whitney, gypsy moth trapping coordinator. "It also helps us determine if an area needs aerial spray treatment the following year or if an egg mass survey needs to be done in the fall to better evaluate the population."

For the time being, little can be done to control the population for 2010.

"There's not much we can do," said Geneva Lake Environmental Agency Director Ted Peters. "The larvae are in the trees and feeding. When we get through summer, we do the egg counts in fall."

But, he said it appears last year's spraying in certain locations was successful.

"We knocked them down in the areas where we sprayed," he said. "We haven't seen a whole lot in those areas."

Several sprays in Linn Township and at Big Foot Beach State Park occurred in the spring of 2009, which Peters considered the worst infestation since 2003. Now, both Peters and Regester haven't received the calls from those areas, but have from the south shore of the Lake Como area.

Regester, the Walworth County University of Wisconsin-Extension horticulture educator, and Peters also said along with spraying in the spring of 2009, cold, wet weather during the same time also has made an impact on this year's possible gypsy moth infestation.

"We'll see what happens," Regester said. "I have received calls from the Wildwood area off of McDonald Road, so it appears to be in the Lake Como area more than Lake Geneva so far."

According to Peters, in 2003, the gypsy moth infestation was relatively localized to the Snake Road area and some other surrounding Geneva Lake areas. However, it was serious enough to force an aerial spraying to suppress the population at that time. There also are a number of natural factors, including normal fluctuations in insect populations, weather conditions and natural predators, that can help limit moth population growth.

"I don't think we have a big problem," Peters said. "It takes a while to get the numbers back up after a good treatment."

According to information from the UW-Extension, gypsy moth outbreaks last from one to three years with about 10 years between outbreaks.

"It's unclear what triggers a population explosion, but they always eventually collapse as a result of natural causes," according to the information.

There are two different traps being used to survey the adult moths — a triangular delta trap which looks like small birdhouse and a mile carton trap. The delta trap can hold up to 20 moths, while the mill carton trap can hold up to 1,5000 moths.

In areas where gypsy moths are known to be, most traps are the milk carton traps. Delta traps are used mostly in the western third of the state where gypsy moths are not as common. There is no trapping in the eastern part of the state because it is considered generally infested and trapping does not provide usable data, Whitney said.

The traps attract male gypsy moths by using pheromone of the female moths as a lure. The traps will be left in place until the moths stop flying in August. The traps also do not allow birds or small mammals to enter.

"It's important to leave the traps up during moth flight to get the data we need," Whitney said. "So, we ask that people leave the traps alone if they see one. Then, after the moth flight ends, we'll take them down."

"They are just assessing the numbers," Peters said of the traps. "There's now doubt they are here. We didn't kill them all, but are they at a high enough number to require a treatment next spring?"

The gypsy moth was first detected in Wisconsin in the mid-1970s in the eastern part of the state. In 1989, the gypsy moth established populations along the eastern shore of the state from Milwaukee to Green Bay. Since then, the moths have been found in nearly every county and the eastern half is recognized as infested, according to the Wisconsin Department of Natural Resources.

The gypsy moth was inadvertently introduced into North America in 1869 in a misguided effort to breed a hardy silkworm.

Regester said if the caterpillar is on a tree it doesn't like, it drops silk and swing on it to a tree it prefers. That's how they move.

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