Posts Tagged: Vespula pensylvanica
The question begged for an answer.
"It's yellowjacket time again. Does anyone have or recommend a good trap?"
A Bay Area beekeeper today sought recommendations from ledEric Mussen, Extension apiculturist with the UC Davis Department of Entomology and Nematology.
Mussen, who recently co-authored "Yellowjackets and Other Social Pests" on the UC IPM website with Michael Rust of UC Riverside, responded candidly.
"There are a number of ways that people try to deal with populations of yellowjackets at this time of year," he told her.
- If you can find the nesting area, a whole colony can be dealt with, directly.
- If you can’t find the nest, then most people resort to trapping, since putting out poisonous baits no longer is legal. You can purchase the yellow plastic traps at hardware and nursery stores, etc. You can catch quite a substantial number of wasps, but that often does not alleviate the problem. Similar traps in the spring, to intercept the foundresses, accomplishes a lot more in the long run. These traps contain a pheromone that attracts the wasps. Put the traps a good distance away from where you hope to have a wasp-free location.
- In many outdoor areas, people will tie a piece of raw meat suspended over a tub of detergent water. The wasps come and gorge themselves, then tumble into the water and drown. Again, this does not mean that you will get them all and no longer be vexed. Also, you may have to deal with other scavengers that will eat old meat.
- If the wasps are going after your bees, this is a good time to put “robbing screens” on the entrances to your hives. They pretty much stop honey bee robbing and they are helpful with wasp problems, too, where the wasp populations are not too high. You can see my idea of a good design at my Bee Briefs on our Entomology website. See Robbing Screen.
Western Yellowjackets (Vespula pensylvanica) like to hang around or nest near apiaries because it's "one-stop shopping," as former UC Davis postdoctoral scholar Erin Wilson, now an assistant professor of entomology at UC Riverside, said at a UC Davis seminar in December 2010.
Yellowjackets prey on honey bees. They raid the hives (killing the adults and brood, and stealing honey) and take the food back to their young.
Yes, it's that time again when beekeepers figuratively "see red" when they see yellow (jackets).
A yellowjacket entering its nest at an apiary. (Photo by Kathy Keatley Garvey)
A yellowjacket sipping water at an apiary. (Photo by Kathy Keatley Garvey)
As the guests dined on seafood, yellowjackets dined on bits of protein left behind.
The half-filled glasses were there to draw the yellowjackets away from the picnic tables. Don't know what was in the plastic glasses, but whatever it was, it did not kill them. It just slowed them down. A little. They jumped in, swam around, and climbed out.
Yellowjackets (genera Vespula) are pests.
"Defensive behavior increases as the season progresses and colony populations become larger while food becomes scarcer," wrote authors Eric Mussen of Uc Davis and Michael Rust of UC Riverside in the newly updated UC IPM Pest Note, Yellowjackets and Other Social Wasps.
"In fall, foraging yellowjackets are primarily scavengers, and they start to show up at picnics and barbecues, around garbage cans, at dishes of dog or cat food placed outside, and where ripe or overripe fruit are accessible. At certain times and places, the number of scavenger wasps can be quite large."
Yes, indeed. Uninvited guests are likely to join your picnic.
The ones we observed were Vespula pensylvanica, commonly referred to as "meat bees" because they like meat, including the hamburgers, hot dogs and other protein you serve at your picnic and at other outdoor outings. They also like sugary drinks.
An excerpt from the Pest Note:
"Usually stinging behavior is encountered at nesting sites, but sometimes scavenging yellowjackets will sting if someone tries to swat them away from a potential food source. When scavenging at picnics or other outdoor meals, wasps will crawl into soda cans and can sting your lips or the inside of your mouth or throat."
Want to know more about yellowjackets and other social wasps? Access or download the Pest Note.
Yellowjackets are attracted to this plastic container. (Photo by Kathy Keatley Garvey)
Close-up of yellow jackets. They soon climbed out and flew away. (Photo by Kathy Keatley Garvey)
What's that? A honey bee and a male yellowjacket on the same blossom?
Honey bees and yellowjackets belong to the same order, Hymenoptera, but different families. The honey bee (Apis mellifera) is in the Apidae family, while the yellowjacket, Vespula pensylvanica, belongs to the family, Vespidae.
When beekeepers open the hives at the adjacent Laidlaw facility, trouble can start between the honey bees and the yellowjackets. It's no secret that female yellowjackets establish their nests near apiaries to prey upon honey bees and their brood. They need the protein for their offspring.
But here they were--the honey bee and the yellowjacket--together.
The first occupant: the honey bee. She began foraging on a rose blossom when suddenly a male western yellowjacket approached her. Seemingly unaware of his presence, she kept foraging. He poked her with his antennae. She ignored him. He crawled up next to her and took a close look at her. She kept foraging.
A few seconds later, he left.
Native pollinator specialist Robbin Thorp, emeritus professor of entomology at UC Davis, later commented: "I can't help but wonder why the male yellowjacket was visiting a rose flower--no nectar there, so no reward for him."
"Maybe he was just checking out the other occupant 'while searching for love in all the wrong places.' "
Indeed, the male yellowjacket may have been looking for a suitable mate.
This one? Definitely not suitable!
Male yellowjacket heads toward a honey bee. (Photo by Kathy Keatley Garvey)
Male yellowjacket checks out the honey bee. (Photo by Kathy Keatley Garvey)
Honey bee continues to forage, while the male yellowjacket crawls away. (Photo by Kathy Keatley Garvey)
They're here. They're there.
The Western yellowjacket (Vespula pensylvanica) likes to hang around bee hives.
If you're a beekeeper, you've probably seen them nesting in a rodent burrow or hollow log near your hives.
At the Harry H. Laidlaw Jr. Honey Bee Research Facility at the University of California, Davis, yellowjackets currently occupy two rodent holes a few feet from the hives. To mark the spot, beekeeper and research associate Elizabeth Frost placed a brick over each nest (see photo below).
The yellowjackets are not welcome.
Members of the Vespula genus are "the most abundant and troublesome wasps in California," according to scientists Jerry A. Powell and the late Charles L. Hogue in their book, California Insects, published by the University of California Press.
"The voracious workers attack everything in the vicinity, from resting insects to pieces of hamburgers on the picnic table," they noted, and "the colonies may become very large by late summer or fall."
Bee breeder-geneticist Susan Cobey, who divides her time between UC Davis and Washington State University, agrees that yellowjackets "can be a big problem. I've seen them kill hives."
Cobey says she's fighting them now in Island County, Washington. "I have only 10 colonies, but these are special--the imports (for bee research). The wasps are always hanging around the entrance harassing the bees."
"I've had to move hives at times because the invasion was decimating the bee population," she said. "They go for the thorax (meat). They especially like the drones being kicked out of the hives in the fall--big and juicy. This is an easy dinner so then they start going in the hives and taking workers."
One way to counter the yellowjacket invasions is to "reduce the size of the entrance so the bees can protect themselves." Also, beekeepers must "keep the hives strong and healthy--yellowjackets pick on the weak."
To decrease the yellowjacket population, beekeepers bait traps in the summer "as the reproductives come out," Cobey says.
Since yellowjackets are meat eaters and honey bees are not--you can use cat food with the bait.
"But the bait must be protected from other critters," Cobey cautions. "You can put in it an empty beehive with a very small entrance."
(Note: Postdoctoral scholar Erin Wilson of the Louie Yang lab, UC Davis Department of Entomology, will speak from 12:10 to 1 p.m., Wednesday, Dec. 1 in 122 Briggs on how yellowjackets are wreaking havoc in Hawaii. Listen live at http://uc-d.na4.acrobat.com/ucsn1/. The seminar later will be archived.)
Emerging from Hole
You want to make sure that Mr. and Mrs. Yellowjacket and all their offspring--plus nephews, nieces, uncles, aunts, cousins and assorted other relatives--aren't on the invite list.
And if you're a beekeeper, you don't want them killing your honey bees. "They pull the bees off at the entrance, dismember them and fly away with the parts--generally the head--to feed to their larvae," said Extension apiculturist Eric Mussen (right) of the UC Davis Department of Entomology.
Indeed, these predatory insects can be a major problem this time of the year.
When Mussen addressed the Santa Clara County Beekeeping Guild on Monday, Oct. 4, he asked the 60 attendees: "How many of you have had significant problems with yellowjackets?"
About eight hands shot up.
What to do?
"It was around a decade ago that we lost the use of flowable microencapsulated diazinon (Knox Out 2FM^® ) as a yellowjacket bait poison," Mussen said in a message he also shared today with the UC Davis Department of Entomology. "As long as the wasps did not taste it, they would take the contaminated bait back to the nests and share it with their brood and other adults. It was amazing! Often in 48 hours the colonies were out of business and the area was clear of yellowjackets."
Recently, a new microencapsulated product, Onslaught^® , containing esfenvalerate, has come on the market to be mixed into yellowjacket baits, Mussen said. Formulating the bait is the same as it was with diazinon--about 1/4 teaspoonful of the insecticide in about 12 ounces of the bait.
Yellowjackets are attracted to many odorous potential foods when their prey runs out and they turn to scavenging, said Mussen, adding that the chemical seems quite a draw when it's mixed with canned, fish-based cat food.
"Try a couple samples of cat food without insecticide to see which product is most attractive to your local yellowjacket population. Then place about three ounces of formulated bait in each trap and things should get better fast."
"You can find this product on the web as Alpine Yellowjacket Bait Station Kit. A multi-year supply (one pint) of microencapsulated esfenvalerate and four bait stations--they look like over-sized, plastic prescription bottles with a hole in the side and a string for hanging--will cost about $85 before shipping. Sounds like a lot of money for a small amount of product, but if you need to clear out the yellowjackets in a hurry--wedding reception, fair, outdoor barbecue, your own peace of mind-- this is a good investment."
And don't even think about inserting insecticidal wasp baits in that empty soda bottle lying on the ground near your picnic table. It's illegal to put pesticides, including insecticidal wasp baits, into used food and drink containers.
"The last thing you would want is for someone to accidentally eat or drink your poisoned bait," he said.