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Yellow jackets & wasps, oh my

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POSTED November 22, 2009 2:17 a.m.
LATHROP – The City of Lathrop has launched a campaign to educate residents on what to do with the recent invasion of wasps and yellow jackets in the Mossdale area.

In the wake of reports received from residents in the west Lathrop residential community about sightings and close encounters with these so-called social wasps, the city has started distributing brochures and sending out mailings that contain information about these insects, plus remedies that they can utilize to fight the wasp infestation.

The council also included this item on their agenda this week as yet another avenue to inform the public about the recent insect invasion and what they need to know about these bugs.

The good news, according to Interim Neighborhood and Community Services Director Becky Enneking, is that with the onset of the colder autumn weather when temperatures dip well below the century mark, the wasps and yellow jackets activity should begin to die down.

As a general rule, she said, the insects’ life cycle starts in early spring when they come out from their winter hibernation. At their growth phase from spring to midsummer, they start to forage for food specifically honing toward sugars and proteins which is the reason they gravitate around barbecues, soda cans, garbage cans, pet food dishes and fruit trees in warmer weather when they interfere with residents’ outdoor activities. Wasps do not thrive in colder temperatures, so from late September to October, the male species mate with the queens then die off, thereby contributing to the insect populations’ decline, Enneking said. Right around now, the fertile queens start to go into winter hibernation until early spring when they come out and start building their nests again in areas where they come in close contact with people: under eaves of buildings, under tiles on tile roofs, sheds and garages. Wasps gravitate toward trees mainly because of the aphids or the honeydew by-product of aphids that they find in abundance there.

“That’s their candy store,” University of California, Davis Professor and Department of Entomology Vice Chairman Lynn S. Kimsey, Ph.D., said of this food-based insect-tree relationship.

Kimsey volunteered her time to speak at the council meeting, on the invitation of Enneking, to provide a more comprehensive understanding of the invading insects, their behaviors and other little-known facts about their life cycles as well as possible eradication measures, and to answer any questions from the council and the audience.

Problem with wasps, yellow jackets not unique to the City of Lathrop
While there was a number of calls from concerned residents in the Mossdale area about wasp stings and yellow jackets sightings and encounters, Enneking said the problem is not unique to Lathrop. She said she contacted the City of Stockton and found out that they have had similar problems. The city gets a call every six months from Weston Ranch for problem bees and wasps. Lathrop has had two complaints about wasps and yellow jackets this year.

The interesting thing, though, is that the problem does not appear to have affected the east side of Lathrop, which is the area east of Interstate 5. But that’s no reason for the residents there to be complacent about it. Professor Kimsey said what is happening at Mossdale is probably only the onset of the infestation and is just now contained in this area.

“Maybe the problem will be on the east side next year,” she surmised, while noting that the insects’ food-foraging habit is to look for food in the trees.

Enneking and city parks manager Nathan Houx said the infestation is probably come the river and riparian areas. Mossdale is right along the San Joaquin River.

How to solve the wasp, yellow jackets problem
Some residents have called City Hall to find out what the city can do about getting rid of the insect problems at or around their properties. One remedy is to spray the trees where the wasps congregate while foraging for food.

Enneking said that if the trees are on city property, “then we’ll take care of it.”

Dhaliwal wanted to know what would happen “if the problem continues and we have to spray.”

City Attorney Sal Navarrete said the city is permitted to maintain public avenues and that spraying would be a “permissible use of public funds.”

However, Professor Kimsey said spraying alone “won’t get (the insecticide) to the nests” of the insects. Powerful insecticides would be needed for this type of eradication.

“It’s a relatively recent problem,” she said, adding they don’t know of any baits at this time that will work in getting rid of the problem.

“At this point, the industry (devoted to this eradication problem) has not found something” that will do the job, she added.

The council asked, so what can residents do?

“Pray for rain,” the professor said with a laugh.

Tile roofs good news to wasps, bad news for residents
On a more serious note, said that what the city can consider is restricting the use of Spanish-style roofing which uses tile materials. The “cupped open ends” of these roof tiles attract not just pigeons, which is another problem for homeowners, but also wasps who find this structural condition ideal for building their nests.

Enneking said residents can also help the city’s efforts by “maintaining their gardens,” harvesting fruits and berries from trees and bushes before they become too ripe and fall on the ground. Those that fall on the ground should be disposed of immediately so as not to attract the insects.

Other ways to reduce the numbers of wasps and yellow jackets near around homes and yards:

• Consider having professional pest control around the home and yard.

• Remove insect nests around the home and yard and spray.

• Don’t overwater gardens. This can lead to soggy conditions which are suitable for the insects’ nest-building.

• Feed pets inside or remove the food bowls immediately after feeding.

• Do not leave food and drinks outside uncovered, or serve them inside the house.

• Make sure garbage lids are closed tightly.

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