Research and Extension Center System
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Research and Extension Center System

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Brown widow spider could be a concern for farmers

Brown widow egg sacs look something like giant pollen balls.
A UC Riverside scientist is asking for the public’s help to track the distribution of brown widow spiders in California. Brown widows’ range, he said, expanded rapidly in Southern California since their introduction in 2003; they may move northward this summer into Central California.

“The brown widow is spreading like wildfire,” said UC Riverside urban entomologist Rick Vetter. "It’s a very prolific pest. People find them by the hundreds in places where they haven’t seen spiders before.”'

The brown widow poses less of a health threat than black widows, but Vetter said there are several reasons why the agricultural community should be concerned about their potential northward migration. Currently little is known about brown widow spider biological control. While black widows prefer low hangouts, it is not yet known whether brown widows will adjust to higher posts in California. If the spiders take up residence in fruit orchards, for example, they could pose a problem for farmworkers.

“Pickers and harvesters won’t want to have these spiders falling down on them,” Vetter said.

Brown widows could also potentially congregate in agricultural shipping containers or packaging.

Brown widow spiders are native to Africa and are established in tropical environments throughout the world. They have been found in Florida for many decades, but only recently expanded their range from Texas through South Carolina, and into Southern California.  As of 2009, the spider was established in Los Angeles, Orange and San Diego counties, and in 2010 it made its way to Riverside, San Bernardino, Ventura and Santa Barbara counties. There have been a few finds in areas further north.

“I’ve gotten three females from Sacramento and three females from Washington (state),” Vetter said. “I’ve gotten no other spiders from those areas, so I don’t know if they will be another infestation area or not.”

Vetter is asking the public to assist in his brown widow spider research by carefully following instructions for collecting and sending brown widow spider specimens to the university. Potential spider collectors should study the photos on his website to learn the characteristics of brown widows. Because the spider is already established in Southern California, Vetter does not need specimens from San Diego, Orange, Los Angeles and the Riverside and San Bernardino-Redlands area. More specimens are welcome from Ventura, Santa Barbara, from Riverside and San Bernardino counties outside of the urban cities in the western part of the counties and from all the rest of California.

For spider shipping instructions, see Vetter’s brown widow spider research page.

Watch an 80-second video for tips on identifying brown widow spiders:

Posted on Tuesday, April 26, 2011 at 3:07 PM
Tags: brown widow (1), spider (1)

Unique lysimeter design aids researchers.

Since the 1960's HREC has maintained a unique research facility - a set of lysimeters. Each lysimeter consists of a steel tank, which is filled with soil, plumbed to collect all water draining out of that soil, and buried into a hill slope so that the soil within the tanks is similar in conditions to blocks of soil found in the natural system.  This unique setup allows researchers to test how different treatments impact the loss of water, nutrients, pesticdes, etc., from ecosystems.  This photo shows HREC's current 72-tank lysimeter facility, recently built by HREC staff with funds from the "National Research Initiative Cooperative State Research, Education and Extension Service".

Posted on Tuesday, April 26, 2011 at 8:58 AM
  • Author: Robert J Keiffer

Western Harvest Mouse resides at HREC

The Western Harvest Mouse (Reithrodontomys megalotis) is locally common throughout the western two-thirds of the of the United States (lower 48 states except for the high Rocky Mtns).  This secretive rodent prefers open mesa habitats with thick grass and forb vegetation and a build-up of dense litter.  At HREC they can be found in the long-ungrazed portions of the Center.  Bristly fur, a long bi-colored tail, and whitish feet are all characteristics of this native species.

Posted on Monday, April 25, 2011 at 8:32 AM
  • Author: Robert J Keiffer

Coast Live Oaks awaken to spring!

HREC is blessed with location as the Center is located at a "hub" of climate zones and maritime influence and soil and elevation differences.   As a result, HREC has over a dozen species of oaks that can be found on on the Center.  Here you see a Coast Live Oak (Quercus agrifolia) with fresh new leaves forming and catkins ready to bloom.   Coast Live Oaks are only found at scattered locations at the lower elevations on the west side of the Center.

Posted on Saturday, April 23, 2011 at 7:19 AM
  • Author: Robert J Keiffer

Springtime welcomes hatching Killdeer at HREC!

Killdeer are the most common species of shorebird that utilize HREC, and the only shorebird species that nests here.  This nest was placed by the parent killdeer in open gravel next to the HREC greenhouse, and was staked by HREC staff to prevent people from walking or driving over the nest.  Two days ago the eggs hatched, and yesterday the "mom" led the precocial chicks, four of them, away from the nest site and down to Parson's Creek gravel bar.

Posted on Friday, April 22, 2011 at 10:47 AM
  • Author: Robert J Keiffer

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