An article in the current issue of California Agriculture, the peer-reviewed journal from the University of California Agriculture and Natural Resources, examines the spread of herbicide-resistant weeds in California and shows how UC researchers and Cooperative Extension specialists are helping growers to understand and manage the factors that drive it.
Five more articles in this special issue of California Agriculture highlight the work of UC Agriculture and Natural Resources on pests and diseases that threaten the state's people, agriculture and natural resources. The commitments to research and outreach profiled in the issue include the Endemic and Invasive Pests Strategic Initiative, the UC Statewide IPM Program and several successful collaborations with regulatory agencies and the agricultural community.
Whether it's pinkeye, bluetongue or poisonous plants, UC maintains a strong network of laboratories and field experts to protect livestock health in California.
Regional alliances of federal, state and university plant diagnostic labs work together to identify and control disease spread.
Managing newly established pests
A regulatory program coordinated by government agencies, scientists and growers successfully contained an infestation that threatened California vineyards.
The 1999 arrival in California of a new Pierce's disease vector, the glassy-winged sharpshooter, posed a major new threat to California vineyards and orchards. A 15-year collaborative effort has successfully contained the sharpshooter and led to major improvements in our understanding of the biology of Pierce's disease, including promising advances in the development of disease-resistant grapevine lines.
Maintaining long-term management
Little or no crop rotation and limited herbicide options have contributed to the rise of herbicide-resistant weeds in orchards, vineyards and rice fields.
The UC Integrated Pest Management Program helps provide management solutions for invasive pests that destabilize IPM programs in agricultural and urban landscapes.
E-edition research article
The spread of the invasive insect in the late 1990s led to increased costs and changes in agricultural practices for grape, citrus and nursery producers.
These articles and the entire October-December 2014 issue are available at http://californiaagriculture.ucanr.edu.
California Agriculture is the University of California's peer-reviewed journal of research in agricultural, human and natural resources. For a free subscription, go to http://californiaagriculture.ucanr.edu or write to firstname.lastname@example.org.
University of California Agriculture and Natural Resources is the bridge between local issues and the power of UC research. UC ANR's advisors, specialists and faculty bring practical, science-based answers to Californians. Visit ucanr.edu to learn more.
- Author: Jeannette E. Warnert
Research by Jim Stapleton, a UC Cooperative Extension advisor based at the Kearney Agricultural Research and Extension Center, was published as Feasibility of solar tents for inactivating weedy plant propagative material in the March 2012 issue of the Journal of Pest Science.
Stapleton, who specializes in plant pathology and integrated pest management, was inspired to conduct the study when a fire crew came upon a patch of Iberian starthistle growing along a stream in the Sierra foothills near Mariposa. Iberian starthistle is a robust, spiny weed native to the Middle East that, left unchecked, can dominate entire landscapes.
“Crews were going through and cutting dried plants and stacking them, but the seeds survived,” Stapleton said. “If you start moving plant material around with viable seeds, seeds are liable to spread, making the problem worse instead of better.”
Iberian starthistle is only one of many exotic, invasive plants that are capable of transforming California’s open areas into useless and unsightly tracts of land. On rangeland, for example, such weeds diminish desirable annual rangeland feed for cattle and wildlife. Weeds can shade out native wildflowers, make recreational areas inaccessible and, in dense infestations, become a fire laddering fuel.
In the past, such weeds may have been stacked and burned, but fire danger and air quality regulations have forced land managers to find alternatives.
“You wouldn’t want to try this on a 40-acre area,” Stapleton said. “Eradication of weeds with solar tents is best suited for small-scale weed infestations in warm climates.”
For the research project, Stapleton constructed three replicate solar tents with concrete rubble, mulberry shoots and clear plastic tarps. He placed johnsongrass rhizomes inside black trash bags along with about one cup of water. The sample bags were left inside the solar tents for 72 hours.
“Regardless of where you are, regardless of financial resources, you should be able to construct a solar tent,” Stapleton said. “Most of the materials needed – rocks and sticks – are easy to find on site.”
Air temperature inside the sample bags rose to 158 degrees Fahrenheit. Over the three days of the experiment, the rhizomes were exposed to temperatures 140 degrees and higher for 10 hours. None of the rhizome segments treated for three days in the solar tents sprouted. In contrast, rhizomes maintained in clear vegetable storage boxes and kept indoors for comparison all sprouted.
UC Cooperative Extension farm advisor Carl Bell, a San Diego area weed expert, tested the process in Lakeside, east of the San Diego metropolitan area, where a group of volunteers were working on restoration of the San Diego River.
“There are a lot of sites in California where volunteer groups are going into canyons and other remote spots to clean up weeds,” Bell said. “They’re going to places with no roads or trails, scrambling over rocks to clean up these areas. They could construct one of these tents and return in a week to find everything in the bags overheated to a point where seeds won’t germinate and rhizomes are dead. They only have to carry out the plastic bags and tarps.”
For the demonstration, volunteers pulled weeds and built solar tents on a parking lot. They invited the public to a workshop at the site a week later.
“When we pulled out the bags of treated material after a week of cooking, it was a gooey mass of vegetative material incapable of regenerating the weeds,” Bell said.
Diagram of suggested solar tent construction:
(a) closed, black plastic trash bag, e.g., 40 gal volume, containing targeted plant material and one pint to one quart of water for free moisture presence; (b) interior framework of woody plant shoots, sitting on (c) rocks, to elevate trash bag above soil surface and allow heat to surround target; (d) sheet of black plastic film on soil surface to assist with heat accumulation and preclude escape of propagative material onto the soil; (e) clear plastic sheet, supported by (f) hoops of woody plant shoots to form a tent over the treatment bag; (g) exterior rocks, soil and/or logs sealing edges of tent canopy to minimize heat loss and preclude escape of propagative material.
(Graphic by Cynthia Stapleton, adapted from Journal of Pest Science 85:17-21. Graphic may be reprinted with credit. High resolution version.)/span>