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Project description

Distribution and control of an exotic pest wasp, the German yellowjacket (Vespula germanica), in Southern California. (02XU028)
Program Exotic Pests and Diseases Research Program
Principal
investigator
P.K. Visscher, Entomology UC Riverside
Host/habitat Landscapes; Structures and Residential
Pest German Yellowjacket Vespula germanica
Discipline Entomology
Review
panel
Urban Systems
Start year (duration)  2002 (Three Years)
Objectives Document the present distribution in Southern California of the German yellowjacket, to guide decisions about control methods for this exotic pest.

Develop a baiting program to reduce problems from this and other yellowjacket wasps where they occur. Specifically, this study has the following goals.

Determine the range and relative abundance of the German yellowjacket in southern California.

Determine the seasonal pattern of German yellowjacket activity, and how it compares with that of native yellowjacket species.

Develop improved baits and strategies for controlling pest yellowjackets.

Project
Summary
Vespula germanica is an exotic yellowjacket wasp which is a nuisance pest in a variety of outdoor settings in California, is a minor public health threat, and potentially a problem in species conservation. This project will document the current distribution of this wasp, and its seasonal activity pattern relative to native yellowjackets. It will identify bait materials and low-impact toxicants that could provide effective control for this and other yellowjacket species, quantify their efficacy, and test abatement procedures. The results will be widely disseminated through numerous cooperators, training workshops for pest control personnel, and a project Web site.
Final report This project made considerable progress toward the goal of controlling German yellowjackets in southern California. Several pesticides were tested for palatability issues with two (fipronil and imidicloprid) being taken in high quantities and, therefore, deemed acceptable for use in eradication tests.

Using fipronil mixed with ground chicken baits in a Claremont Park, the German yellowjacket population was eliminated within hours. Subsequent monitoring in the following weeks showed no resurgence of German yellowjacket populations in that park indicating that a very short experimental exposure of fipronil was sufficient to destroy the colony completely.

Additional early-season testing demonstrated that queens and early season workers also scavenge ground chicken baits, signifying that it seems feasible to attempt yellowjacket control early in the year before populations reach pestiferous levels.

Third-year
progress
The progress in the last year is moving toward the goal of controlling German yellowjackets in southern California. Several pesticides were tested for palatability issues with two (fipronil and imidacloprid) being taken in high quantities and, therefore, deemed acceptable for use in eradication tests. Using fipronil mixed with ground chicken baits in a Claremont Park, the German yellowjacket population was eliminated within hours. Subsequent monitoring in the following weeks showed no resurgence of German yellowjacket populations in that park indicating that a short experimental exposure of fipronil was sufficient to destroy the colony completely. Additional early-season testing demonstrated that queens and early-season workers also scavenge ground chicken baits signifying that it seems feasible to attempt yellowjacket control early in the year before populations reach pestiferous levels.

Second-year
progress
We have mapped much of the distribution of the German yellowjacket (Vespula germanica) in southern California, including Orange, Los Angeles, and western Riverside Counties. German yellowjackets are most commonly found in the lowlands, replaced by the native western yellowjacket (Vespula pensylvanica) near the foothills. These two species are the most common pest yellowjackets in southern California. Information on their distribution is important for determining control strategies due to differing food preferences. Without this information control efforts could be directed to the wrong wasp or using the wrong bait.

We have developed a website (http://wasps.ucr.edu), including general information on yellowjacket wasps in southern California, an illustrated key to local species, and other information. This medium is reaching a wide audience among the millions of people in coastal southern California.

Presentations to the Entomological Association of Southern California and at the annual UC Riverside Urban Entomology Conference, have alerted approximately 300 entomologists and pest control personnel to the existence of our research and the need for cooperation from their disciplines.

In the control studies, we have found that heptyl butyrate, which is used, as an attractant for western yellowjackets is unattractive to German yellowjackets. Furthermore, other chemical baits reported attractive to German yellowjacket had minimal effect in this region. We have compared the attractiveness and amount taken of a number of meat-based foods that can be used for survey work and will be used as carriers for toxicants as we develop control strategies for German yellowjackets.

First-year
progress
We have started to map the distribution of the GYJ in southern California, concentrating in Orange County. Knowledge of this distribution will be important for determining control strategies due to differing food preferences of these two species (by far the most common pest yellowjackets in southern California). It will be important for pest control personnel to know which species they are working with; otherwise they might be trying to control the wrong wasp or use the wrong bait. Our results so far agree with prior anecdotal reports of GYJ being most commonly found in the flatland sections and replaced by the native western yellowjacket (Vespula pensylvanica) in proximity to the foothills.

We have posted a new website (http://wasp.ucr.edu) with information on yellowjacket wasps in southern California, including general information, an illustrated key to local species, and solicitation of yellowjacket samples from the public to expand our database. We expect this medium to reach a wide audience among the millions of people in coastal southern California, and will continue to update the information as this project develops.

The results so far have been presented to the Entomological Association of Southern California and at the annual UC Riverside Urban Entomology Conference, thereby alerting approximately 300 entomologists and pest control personnel to the existence of our research and the need for cooperation from their disciplines.

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