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September 14, 2007

UC scientists find answers about Sahara mustard's spread

Sahara mustard's sweep into Death Valley National Park and other southwestern deserts has caught the attention of UC scientists and California land managers.

   Native annual desert pincushion, Chaenactis stevioides, surrounded by Sahara mustard seedlings.
  

Native annual desert pincushion, Chaenactis stevioides, surrounded by Sahara mustard seedlings.
Photo by Robin Marushia

Sahara mustard is a member of the mustard family and native to North Africa, the Middle East, and southern Europe. It has spread to the southwestern United States, including southern Nevada, and has invaded native Mojave Desert shrublands.

The mustard's seed is spread when dry plants break off and tumble in the wind.  Animals and humans also spread it when it becomes wet and sticky. The drought-tolerant mustard thrives in sandy soils of beaches, dunes, and roadsides. It threatens native desert vegetation by using soil moisture and mineral nutrients needed by native plants.

Plant physiologist Jodie Holt and PhD student Robin Marushia from UC Riverside designed a field experiment to track Sahara mustard and compare its growth, survival, reproduction, and dominance against the same measurements in the native plant community.

"We found that not only does Sahara mustard grow and reproduce more quickly than native plants, but it also tends to survive and reproduce at a higher rate," says Marushia. "These results are important for land management because it suggests that there could be a short window of time between native plant and Sahara mustard growth when we could selectively control Sahara mustard. Our results indicate that it invades areas that are rich with native annual wildflowers, and land managers can target these areas first with prevention and control efforts."

"Sahara mustard appears to exhibit an escape strategy that allows it to thrive in the Mojave Desert environment," says Holt. "In experiments, Sahara mustard grows rapidly under a wide range of environmental conditions. Early, rapid, plentiful growth may allow it to take over resources and gain an early competitive edge over native annuals that have more precise germination requirements."

Results are being used to test control strategies for Sahara mustard and identify areas most susceptible to invasion and on which to focus control.

The field project also provides land managers with information about the timing of Sahara mustard's life stages, such as the rosette and flowering stages, the ideal time to control the weed through hand-pulling.

"We also plan to study Sahara mustard's distribution based on climate," says Marushia. "This information could help land managers to predict and map its spread."

The UC Exotic/Invasive Pests and Diseases Research Program funded this project.

The UC Exotic/Invasive Pests and Diseases Research Program targets research on exotic pests and diseases in California. The program aims not only to improve our knowledge and management of pests that are already here, but also to reduce the potential impact of those pests and diseases that pose a threat to the state. The program is a collaboration between the UC Statewide Integrated Pest Management Program and the UC Riverside Center for Invasive Species Research. U.S. Department of Agriculture, Cooperative State Research Education and Extension Service, funds the program.

Resources

High-resolution image (1MB) "Native annual desert pincushion, Chaenactis stevioides, surrounded by Sahara mustard seedlings." Photo credit: Courtesy of UC Riverside, Robin Marushia.

High-resolution image (500KB) "Researcher Julie Proctor from US Geological Survey measures plants on Rasor Road, the site of the researchers' Sahara mustard field experiments between Interstate 15 and the Mojave National Preserve." Photo credit: Courtesy of UC Riverside, Robin Marushia. Photos are for use with this release only. All other uses see Legal Notices.

Exotic and Invasive Pests

Contacts

Stephanie Klunk, Communications Specialist
UC Statewide IPM Program
(530) 754-6724

Jodie Holt, Plant Physiologist
Botany and Plant Sciences
UC Riverside
(951) 827-3801

Robin Marushia, PhD
Botany and Plant Sciences
UC Riverside

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