Last winter’s bone-chilling cold wasn’t good for much except pushing up heating bills and freezing fingers and toes, but it may have also contributed to slowing the spread of gypsy moths.
On the heels of a record number of gypsy moths caught in Minnesota in 2013, with over 90 percent of those caught in Cook and Lake county, the state of Minnesota placed a quarantine on both counties restricting the movement of pulp wood, firewood, trailers, and other items that might transport the gypsy moths or their larvae. It was Minnesota’s first quarantine ever, and it came after years of treating the pests with pesticides.
In 2013, 71,262 moths were caught statewide. Of those, 62,243 were trapped in Cook and Lake counties.
But one of the coldest winters on record last year seems to have helped contain the leaf-eating pest that is now wholly or partially quarantined in 23 states.
“Yes, we do believe the record cold temperatures coupled with the cold, wet, spring did have a negative impact (from a management standpoint, a positive impact) on the gypsy moth population in Minnesota. In fact, this was seen nationwide,” said Thielen Cremers, director of the Minnesota Department of Agriculture Gypsy Moth Program.
“In 2014, we caught 522 total moths statewide, with 105 being caught in Lake and Cook counties,” said Cremers.
Part of the reason fewer moths were caught was because there were fewer traps set.
“In 2014, we placed a total of 552 traps in Cook and Lake counties, a decrease of approximately 48 percent from the total traps placed during the 2013 survey season. It is common that we place fewer detection traps within areas that become quarantined since the goal of our survey program is to detect newly established populations out in front of the generally infested area,” Cremers said.
“Cook and Lake counties would be considered generally infested. In addition, it would not be uncommon for us to pick up less moths due to the significant decrease in survey traps placed within Lake and Cook counties. However, I’m sure that’s not the whole story.
“I don’t think I need to remind anyone, but the 2013-14 winter broke a lot of records and was one of the coldest winters on record. The National Weather Service documented the 2013-14 winter as the coldest meteorological winter in 35 years!” said Cremers.
Cremers noted that the 65 days following December 1, 2013 broke the below zero record for cold by 6 days. The previous record was set in 1958-9, 1916-1917, “as well as the winter of 1874-1875.”
She also said that December 2013 was one of the snowiest on record.
Future of the Gypsy Moth Quarantine
Brought to America in 1868 to Boston, the moths slowly made their way west, following the food trail. The moths are especially damaging to oak trees, defoliating them and leaving them weak and less resistant to disease, causing millions of dollars of damage.
Because of the damage the moths can do, the quarantine won’t end anytime soon, said Cremers. With few natural enemies in North America, the moth will continue to spread, but states like Minnesota are trying to slow the spread through quarantines.
“The MDA along with federal, state, local and tribal partners, examined several years of data before proposing quarantine for Lake and Cook counties. It would be premature, after one year of population drop, to say the quarantine will be pulled back, and multiple years of data would need to be examined to make that determination. Therefore, it is much too early to tell what future gypsy moth population numbers will be in the coming years.
“We do know, however, that we cannot count on Mother Nature to keep our population in check. Gypsy moth populations can rebound once established. In fact, despite low numbers our most significant trap capture was in Lake County this past season.
“The MDA will continue to monitor the gypsy moth population in Minnesota and will evaluate the situation each year to assure we are slowing the movement of this devastating pest into new areas of the state,” Cremers said.
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