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Yellowjackets out in force this summer

Looking for moisture, more of these wasps are likely to show up in your garden


Yellowjacket on a piece of wood
This is a western yellowjacket. They're beneficial
insects, but will sting if their nest is disturbed.
(Photo courtesy UC IPM)



Watch where you step; it’s yellowjacket season.

Late July and August are peak times for yellowjacket encounters, especially during a drought. As it searches for water sources, this familiar black wasp with distinctive yellow markings is more likely to fly into irrigated landscapes. Quite often, they’ll hang out on lawn as they search for grubs and caterpillars as well as moisture.

Because they eat so many destructive plant-eating insects, yellowjackets are considered very beneficial, and not a pest. Unless they start stinging.

Yellowjackets will sting – a lot – if their nest is disturbed. That likely was the case earlier this week when six tourists to the Sonoma Coast were stung repeatedly by yellowjackets after one of them fell into a nest near Goat Rock State Beach; the others were stung as they tried to help. Two women, ages 68 and 70, were flown to a local hospital.

Yellowjackets also are attracted to dropped fruit under trees. They like flower nectar (and help with pollination). With a craving for meat and sweets, their favorite “food” is people’s garbage; they’re known for buzzing trash cans – as well as outdoor picnics or barbecues.

Unlike paper wasps that build open-honeycombed nests in eaves and other protected spaces far above ground, yellowjackets like the cool of the earth. They opportunistically build their nests (which are enveloped in paper) in abandoned gopher burrows, gaps in walls or holes in the soil. Or they may make their home inside an irrigation valve housing – it’s cool and connected to its own water source.

One nest or colony may be home to hundreds, even thousands, of yellowjackets. Once yellowjackets discover a source or food or water, they’ll return often to hover at that location – even after the food is gone.

People usually can get along with yellowjackets as long as they respect their space, according to experts.

“In Western states, there are two distinct types of social wasps—yellowjackets and paper wasps,” explains the UC master gardeners. “Yellowjackets are by far the most troublesome group, especially ground- and cavity-nesting ones such as the western yellowjacket, which tend to defend their nests vigorously when disturbed. Defensive behavior increases as the season progresses and colony populations become larger while food becomes scarcer.

“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,” added the master gardeners. “At certain times and places, the number of scavenger wasps can be quite large.”

Cover your drinks. Scavenging yellowjackets have been known to crawl into soda cans and sting unsuspecting sippers.

“Paper wasps are much less defensive and rarely sting humans,” noted the master gardeners. “They tend to shy away from human activity except when their nests are located near doors, windows, or other high-traffic areas.”

In your home garden, be careful while weeding. It’s easy to unearth a nest while pulling tall grasses or step in an occupied hole. (Personally, I’ve done both.)

Because they are beneficial insects, yellowjackets have an important place in the landscape. “(They) should be protected and encouraged to nest in areas of little human or animal activity,” say the master gardeners.

“The best way to prevent unpleasant encounters with social wasps is to avoid them,” say the master gardeners. “If you know where they are, try not to go near their nesting places. ... Be on the lookout for nests when outdoors. Wasps that are flying directly in and out of a single location are probably flying to and from their nest.”

Keep garbage covered and, when eating outdoors, cover food and drink, too.

And watch where you step.

For more on yellowjackets and paper wasps:
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7450.html This page also has a helpful video on distinguishing yellowjackets from lookalike insects.


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Garden checklist for week of May 31

Remember to water early. No more rain is in the immediate forecast.

* It’s not too late to transplant tomatoes, peppers, eggplant or other summer favorites. Make sure they stay hydrated.

* From seed, plant corn, melons, pumpkins, radishes, squash and sunflowers.

* Plant basil to go with your tomatoes.

* Transplant summer annuals such as petunias, marigolds and zinnias.

* It’s also a good time to transplant perennial flowers including astilbe, columbine, coneflowers, coreopsis, dahlias, rudbeckia, salvia and verbena.

* Let the grass grow longer. Set the mower blades high to reduce stress on your lawn during summer heat. To cut down on evaporation, water your lawn deeply during the early hours of the morning, between 2 and 8 a.m.

* Tie up vines and stake tall plants such as gladiolus and lilies. That gives their heavy flowers some support.

* Dig and divide crowded bulbs after the tops have died down.

* Feed summer flowers with a slow-release fertilizer.

* Mulch, mulch, mulch! This “blanket” keeps moisture in the soil longer and helps your plants cope during hot weather.

* Cut back fruit-bearing canes on berries.

* Feed camellias, azaleas and other acid-loving plants. Mulch to conserve moisture and reduce heat stress.

* Cut back Shasta daisies after flowering to encourage a second bloom in the fall.

* Trim off dead flowers from rose bushes to keep them blooming through the summer. Roses also benefit from deep watering and feeding now. A top dressing of aged compost will keep them happy. It feeds as well as keeps roots moist.

* Pinch back chrysanthemums for bushier plants with many more flowers in September.

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Dec. 16: Add asparagus to your edible garden

Dec. 9: Soggy soil and what to do about it

Dec. 2: Plant artichokes now; enjoy for years to come

Nov. 25: It's late November, and your peach tree needs spraying

Nov. 18: What to do with all those fallen leaves?

Nov. 11: Prepare now for colder weather in the edible garden

Nov. 4: Plant a pea patch for you and your garden

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Oct. 20: Change is in the autumn air 

Oct. 13: We don't talk (enough) about beets

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Sept. 30: Seeds or transplants for cool-season veggies?

Sept. 23: How to prolong the fall tomato harvest 

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Sept. 16: Time to shut it down? 

Sept. 9: How to get the most out of your pumpkin patch

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Aug. 19: Put worms to work for you

Aug. 12: Grow food while saving water

Aug. 5: Enhance your food with edible flowers

July 29: Why won't my tomatoes turn red?

July 22: A squash plant has mosaic virus, and it's not pretty

July 15: Does this plant need water?

July 8: Tear out that sad plant or baby it? Midsummer decisions

July 1: How to grow summer salad greens

June 24:  Weird stuff that's perfectly normal

SPRING

June 17: Help pollinators help your garden

June 10: Battling early-season tomato pests

June 3: Make your own compost

May 27: Where are the bees when you need them?

May 20: How to help tomatoes thrive on hot days

May 13: Your plants can tell you more than any calendar can

May 6: Maintain soil moisture with mulch for garden success

April 29: What's (already) wrong with my tomato plants?

April 22: Should you stock up on fertilizer? (Yes!)

April 15: Grow culinary herbs in containers

April 8: When to plant summer vegetables

April 1: Don't be fooled by these garden myths

March 25: Fertilizer tips: How to 'feed' your vegetables for healthy growth