Posts Tagged: weeds
A team of researchers has received a $5 million grant from the U.S. Department of Agriculture to find new ways to combat Johnsongrass, one of the most widespread and troublesome agricultural weeds in the world.
"Johnsongrass is a huge problem," said Jeff Dahlberg, UC Cooperative Extension sorghum specialist and director of the UC Kearney Agricultural Research and Extension Center in Parlier, Calif. "It impacts many different crops and is very hard to control."
Dahlberg is part of the team that includes scientists from Virginia, Kansas, North Carolina, Texas and Georgia. Andrew Paterson, director of the Plant Genome Mapping Laboratory at the University of Georgia, Athens, is the lead investigator.
Native to the Mediterranean region, Johnsongrass has spread across every continent except Antarctica. It was introduced to the U.S. in the 1800s as a forage crop, but it quickly spread into surrounding farmland and natural environments, where it continues to cause millions of dollars in lost agricultural revenue each year, according to the USDA.
The naturalization of Johnsongrass across much of the U.S. has also allowed the plant to develop attributes — such as cold and drought tolerance, resistance to pathogens and the ability to flourish in low-fertility soils — that make it particularly difficult to control. Adding to the challenge is the adoption of herbicide-resistant crops around the world.
"Herbicide-resistant crops have been associated with a dramatic increase in herbicide-resistant weeds," Patterson said. "With 21 genetically similar but different types of Johnsongrass known to be resistant to herbicides, it will only become more problematic in the future."
Over the course of their five-year project, the researchers will work to better understand the weed's capabilities and the genes that make Johnsongrass so resilient. Johnsongrass [Sorghum halepense] is closely related to sorghum [Sorghum bicolor (L.) Moench], a healthy gluten-free grain, animal feed and biofuel crop. Lessons learned from the Johnsongrass research may lead to strategies to improve sorghum.
For his part, Dahlberg plans to use the global information system (GIS) to map the locations of Johnsongrass in California to better record its distribution in the state and to help understand how it spread into California by relating it to other populations of johnsongrass in the U.S.
"Ideally, we will use an app to map, identify, manage, and catalog populations that have developed different traits – such as susceptibility to plant disease, ability to host a particular insect, or resistance to herbicides," he said.
This information may lead to new management strategies that curb its growth, providing farmers with more options to combat the invasive plant. The researchers also hope that learning more about the fundamental structures that give Johnsongrass its unusual resilience will pave the way for new genetic tools to improve useful plants, such as sorghum.
Other researchers working on this project are Jacob Barney, Virginia Tech; C. Michael Smith, Kansas State University; Wesley Everman, North Carolina State University; Marnie Rout, University of Texas, Temple; and Clint Magill and Gary Odvody, Texas A&M University.
An initiative to manage endemic and invasive pests and diseases is part of UC Agriculture and Natural Resources Strategic Vision 2025.
Dry beans are an important rotational crop in the Southern San Joaquin Valley. They are not a high value crop, so effective growing and marketing practices are a priority. The dry bean meeting held at Kearney on August 27, 2013 attracted about 30 attendees. It focused on many aspects of new crop management and marketing strategies to improve the return per acre of dry beans.
There were four field presentations. Larry Schwankl, UC Cooperative Extension irrigation specialist at Kearney Agricultural Research and Extension Center, and Carol Frate, UC Cooperative Extension advisor in Tulare County, alfalfa, dry beans, corn and plant pathology, discussed a subsurface drip irrigation trial for blackeye production. Carol Frate discussed the evaluation of insecticides for lygus bug management. Phil Roberts, chair and professor in the Department of Nematology at UC Riverside, nematode host-parasite relations, genetics and pest management in field and vegetable crops, discussed screening bean varieties and breeding lines for root knot nematode resistance. Phil Roberts and Bao Lam Huynh discussed developing new varieties of beans for insect and disease resistance.
Indoor sessions included PowerPoint presentations and related discussions. Gary Luckett, manager of the Cal-Bean & Grain Warehouse, provided an update on the blackeye market. Bao Lam Huynh discussed using marker-based techniques for developing new blackeye varieties. Kurt Hembree, UC Cooperative Extension advisor in Fresno County, weed management strategies in crop and non-crop settings, discussed past, present and future methods of weed control in dry beans.
The meeting provided:
- PCA hours: 1.5 hours of “other”
- CCA hours: 1.5 hours of IPM; 0.5 hours of crop management
Research by Jim Stapleton, a UC Cooperative Extension advisor and Statewide Integrated Pest Management Program Coordinator for Natural Resources, 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 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.
Annotated diagrams for suggested construction of solar tents can be found on the UC Solarization website.
Soil solarization involves covering a field with clear plastic mulch to trap solar radiation in moist soil. During the hot summer months, the soil temperature can rise to levels that can kill soilborne diseases, nematodes and weed seeds. This system has proven especially useful to small-scale, limited-resource and organic growers who produce specialty crops in warm climates.
Last summer’s research, coordinated by Kearney-based integrated pest management plant pathologist Jim Stapleton, was part of a bi-national, multi-institution collaborative effort led by UC Davis biological and agricultural engineering professor Jean VanderGheynst. The research was funded with a grant from the Binational Agricultural Research and Development Fund, which supports agricultural research in Israel and the U.S. that is mutually beneficial.
Environmental science students at Fresno Pacific University, under the supervision of professor and project collaborator Ruth Dahlquist, were enlisted to carry out some of the research on micro plots at Kearney. They subjected black mustard seed to a solarization regimen that mimicked typical farming conditions to study the effects of the treatment on the seeds and the physical and biological properties of the soil.
Two of the Fresno Pacific students were honored by the California Weed Science Society at its annual meeting in January for posters they developed based on their research findings. DeeAnn Kroeker earned first place in the student poster contest for her analysis of the effects of volatiles produced during solarization of compost-amended soil on black mustard seed inactivation. Kate Hernandez was awarded third place for her poster about the field effects of solarization and compost treatment on inactivation of black mustard seed.
The research at Kearney continues during the summer of 2012.
The Israeli counterpart of the solarization research is focused on the impact of a different type of compost and solarization on fungal plant pathogens in the soil.