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JOB ANNOUNCEMENT :: Weed Ecology and Management for Specialty Crop Systems Professor

https://academicjobsonline.org/ajo/jobs/12712 Section of Horticulture - Geneva, Cornell University Position ID: Cornell-Section of Horticulture - Geneva-AAP [#12712, WDR-00017043] Position Title:  Weed Ecology and Management for...

Posted on Wednesday, December 5, 2018 at 9:22 AM

Why mud daubers are on spider patrol

UC Cooperative Extension advisors are on the front line and get the most interesting questions from our community. Someone brought some wasps into our office, and was worried they were invading her home, and wondered how to get rid of them. They were identified by the UC Davis Entomology Museum as black and yellow solitary mud dauber wasps, which are natural predators of spiders, and hence beneficial! Before you reach for that can of insecticide or heaven forbid, a blow torch to control spiders, talk to a UCCE advisor or Master Gardener in your county and read this blog for more information on managing them.

Yellow and black mud dauber wasps are predators of spiders but harmless to people. Adults are about 1-inch in length with true wasp waists!

Here's all you need to know about mud daubers and spider control

That mud you track into your house is nothing compared to what mud daubers can do — and what they do to spiders. Female mud daubers, or wasps, build mud nests for their young — and provision them with spiders.

Where are the nests and what do they look like?  

Female mud daubers, the architects, build those characteristic rectangular mud nests in protected areas of our homes, shops and garages, such as along eaves, walls or ceilings. Mud daubers are black and yellow solitary wasps (Sceliphron caementarium) that hunt spiders for their young. Another wasp, the blue mud wasp, reuses the black and yellow mud dauber wasp nests and primarily preys on black widow spiders.

Mud dauber wasp nests with holes where adults have exited after completing their immature stages.

Do mud daubers sting or bite? 

Mud daubers do not aggressively protect their nests. Unlike hornets and other social wasps, they are generally docile and rarely sting. 

Are mud daubers dangerous?

No, mud daubers are harmless and actually beneficial. They prey on spiders, including black widows, a favorite prey. They pack each cell with up to 25 to 30 spiders for their young. With about 15 to 20 cells per nest, that's over 500 spiders eaten. This is good news, especially for those of us who fear black widow spiders. True, mud daubers can be a nuisance, as their mud nests look messy, but they are generally peaceful.

How do they make their nests?

Females construct their nests by gathering globs of mud in their mandibles (jaws) from a nearby source of wet dirt. They carry the mud to a protected nest site, where they construct a cell. Then they begin hunting for spiders to provision the cell for their young, and lay a single egg inside. When they capture a spider, they sting it, permanently paralyzing it. This preserves the spider until their larvae are ready to eat it. When the cell is full of spiders, the female mud dauber caps it with more mud and builds another cell next to it. After the egg hatches and the food gone, she pupates. When an adult emerges, it opens the cap, leaving holes behind in the nest for the next cycle.

Mud daubers have a low reproductive rate, with about 15 to 20 eggs per female. Adults are active during the day during spring and summer with multiple generations per year. Queens overwinter in the cells in the larval stage. Adults sip nectar from flowers, where the male mud daubers are often found. Mud dauber wasps have good vision and use landmarks to locate nests and hunt spiders. They prefer protected areas where there are plenty of spiders. Sometimes you might see them going in and out of your house vents, hunting for spiders in your basement or attic.

Mud dauber pupa (right) and cells packed with spiders, showing the importance of these wasps for providing natural spider control.

How do mud daubers avoid being eaten by spiders?

Some are able to land on webs without getting entangled, and pluck the web to simulate an insect in distress. When the spider rushes to capture its prey, it becomes a victim of the wasp's paralyzing sting. The wasp then carries it back to her mud nest.

How do you get rid of mud dauber nests?

Although mud daubers are considered beneficial, you can remove the nests by scraping them off with a paint scraper or a knife into a dust pan, and then tossing them or moving them somewhere else where you don't mind their activity. The best time to remove the nests is in the late evenings when wasps are not active, or during the wintertime when they are dormant.

Do I have to worry about getting stung by a wasp or bit by a spider during nest removal?

No, the spiders are paralyzed and the wasps are not aggressive. Mud daubers can sting, but only if directly handled or if they accidentally snag in your clothing.

What's the best way to get rid of spiders?

Overall, spiders are beneficial because they're predators and feed on pests like flies. Most spiders cannot harm people. Those that might injure people — for example, black widows — generally spend most of their time hidden under furniture or boxes, or in woodpiles, corners or crevices. The spiders that we commonly see out in the open during the day are not aggressive toward people. The brown recluse spider has occasionally been brought into California in household furnishings, and other items, but it does not reside here. Spiders enter houses and other structures through cracks and are also carried inside on plants, firewood and boxes. 

According to the UC IPM Spider Management Guidelines, the best approach for controlling spiders in and around your home is to remove hiding spots for secretive spiders such as black widows, and regularly brush or vacuum webs from windows, corners of rooms, storage areas, basements and other seldom used areas. This is effective because their soft bodies generally cannot survive this process. If you see a dust-covered web indoors, it's no doubt an old web that a spider is no longer using.

Why should one protect mud dauber nests?

Because mud daubers eat spiders, especially the cryptic black widows. In the process of cleaning spiders and webs, be sure to try protect those mud nests, because mud daubers naturally help control spiders in and around your home.

Blue mud wasp adults favor black widow spiders. Photo credit: University of Florida Extension.
Posted on Tuesday, December 4, 2018 at 8:05 PM

Field scouting guide: Palmer amaranth

Poor control of Palmer amaranth can result in a significant infestation late in the season and crop failure. Photos by the late Dr. Ted Webster, Research Agronomist with USDA-ARS

From Growing Produce by Karli Petrovic | November 27, 2018https://www.growingproduce.com/vegetables/field-scouting-guide-palmer-amaranth/ Field Scouting Guide: Palmer Amaranth This month's field scouting guide concentrates on Amaranthus palmeri S....

Posted on Tuesday, December 4, 2018 at 9:42 AM

New weed control options for leeks

Photo 1. Weeds in untreated

Richard Smith is a University of California Cooperative Extension Farm Advisor in Monterey County.   Leeks are in the onion family and are increasingly important crop in Monterey County. In 2017, there were 475 acres produced worth $8.6 million....

Posted on Tuesday, November 27, 2018 at 2:20 PM

Organic farmers and researchers strive to advance soil care

Organic farmer Phil Foster has developed a creative way to nurture the soil on his 200-acre farm near Hollister. He plants cover crops in a single line at the top of the planting bed, saving water and seed while keeping the furrows clear for irrigation.

"We were finding we couldn't use cover crops because of water," Foster said. The narrow strip makes the best use of the limited water supply, while garnering the benefits of cover crops - which buffer soil temperatures, inhibit weeds, increase soil microbial activity, improve water infiltration and add nutrients. Growing cover crops prepares the soil for the production of high-quality vegetables.

Organic farmer Phil Foster stands in front of a field with cover crops planted in strips at the top of the planting bed.

Foster is one of eight organic vegetable growers who are working with researchers at Chico State, Fresno State and UC Agriculture and Natural Resources on a project funded with a USDA grant designed to make significant improvements in soil care in organic production systems. He guided project participants around his farm, equipment yard and compost operation in early November to share the techniques he and his staff have developed over three decades to promote soil health.

Tiny pores and roots can be seen in the soil at the Foster farm.
 
UC Cooperative Extension farm advisor Sarah Light examines a soil sample. The agronomy expert, who serves Yuba, Sutter and Colusa counties, is a cooperator on the project.

Tour participants marveled at the soil characteristics, admiring tiny pores and roots in clods of dirt, evidence of the soil's capacity to move water and nutrients. They studied the plant and soil conditions after farm manager Efrain Contreras pulled a carefully crafted implement for rolling down the cover crop across the field with a tractor. 

Foster credited Contreras, a 30-year employee, for his role in building the soil on the farm. Labor, Foster said, is his biggest cost. He has 50 full time staff, many with 5 to 20 years of experience.

"They are the key to to the success of the ranch," Foster said.

Farm manager Efrain Contreras pulled an implement through a mature cover crop to show how the field can be prepared for planting.

Minimizing and, eventually eliminating, soil disturbance can be combined with organic groundcover, year-round root growth and robust biological activity in the soil to further promote soil health. Following the tour, the farmers talked about ways to attain the goal on their farms of no-till organic vegetable production. 

Foster said he will experiment with reducing soil disturbance to determine whether doing so will maintain or increase yields. Another farmer in the project, Scott Park of Meridian, Calif., 50 miles north of Sacramento, said he will dedicate eight acres of his organic farm to comparing the results when the cover crop is chopped and left on the soil surface to chopped and incorporated with tillage.

Paul Muller and Andrew Braitt of Fully Belly Farm in the Capay Valley suggested the researchers could help the farmers by identifying optimal, effective cover crop rolling techniques. Retired organic farmer Tom Willey of Madera suggested grant funds be used to purchase appropriate scale cover crop seeders for on-farm experimentation.

"We're making great progress," said project coordinator Jeff Mitchell, UC Cooperative Extension vegetable crops specialist. "By getting together regularly, we're seeing opportunities for moving further toward reduced-disturbance on the farms, identifying the equipment needs and establishing effective channels of communication."

Over the project's three-year term, the farmers and researchers will continue to experiment with soil-building techniques and share results.

Andrew Brait of Full Belly Farmers, foreground, looks at roots and nodulation of rhizobia on the cover crop. Kelly Mulville and Esther Park of Paicines Ranch are in the background.

 

A safflower and vetch cover crop growing in the autumn light.

 

Workers, in the background, manually weed the safflower and vetch cover crop.

   

Project coordinator Jeff Mitchell, UC Cooperative Extension vegetable crops specialist, and Phil Foster.
 
UCCE farm advisor Amber Vinches, center with sun glasses, is a cooperator on the project. Vinchesi serves vegetable crop farmers in Colusa, Sutter and Yuba counties.
Posted on Monday, November 26, 2018 at 8:35 AM

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