Californians can help in the fight against invasive species by learning and participating during California Invasive Species Action Week, June 2–10.
During the week, the UC Statewide Integrated Pest Management Program invites the public to spend lunch learning about invasive tree killing pests, aquatic nasties like quagga mussels and nutria, and how the invasive weed/wildfire cycle is altering our ecosystems. http://ucanr.edu/sites/invasivelunch/
The invasive species killing trees is causing sugar volcanoes to erupt on avocado trunks and branches that might be infected with Fusarium dieback. Fusarium dieback is a invasive, beetle-vectored disease that causes damage on avocado and more than 39 other tree species. The disease has spread in urban forests and wild lands in the Los Angeles basin since early 2012, and in Orange and San Diego counties since early 2013 and Ventura County in 2015.
The symptoms — staining, sugary exudate, gumming and beetle frass — are often noticed before the tiny beetles (1.5–2.5 mm) are found.
As its name suggests, these beetles bore into trees. Near or beneath the symptoms, you might notice the beetle's entry and exit holes into the tree. The female tunnels into trees forming galleries, where she lays her eggs. Once grown, the sibling beetles mate with each other so that females leaving the tree to start their own galleries are already pregnant. Males do not fly and stay in the host tree.
Shothole borers have a special structure in their mouth where they carry two or three kinds of their own novel symbiotic fungi. Shothole borers grow these fungi in their tree galleries. It's these fungi that cause Fusarium dieback disease, which interrupts the transportation of water and nutrients in the host tree. Advanced fungal infections will eventually lead to branch dieback.
Early detection of infestations and removal of the infested branches will help reduce beetle numbers and therefore, also reduce the spread of the fungus.
- Chip infested wood onsite to one inch in size or smaller. If the branch is too large to chip, solarize them under a clear tarp for several months
- Avoid movement of infested firewood and chipping material out of infested area
Avocado is one tree host. Shothole borers successfully lay eggs and grow fungi in many tree hosts, with some of these trees susceptible to the Fusarium dieback disease. For more information about tree host species, where the shothole borer is in California, and what symptoms look like in other tree hosts, visit the UC Riverside Eskalen Lab website or the Invasive Shot Hole Borers website.
Content in this post taken from the UC IPM Avocado Pest Management Guidelines. Faber BA, Willen CA, Eskalen A, Morse JG, Hanson B, Hoddle MS. Revised continuously. UC IPM Pest Management Guidelines Avocado. UC ANR Publication 3436. Oakland, CA.
Sweeping acres of striking golden flowers may soon grace California's desert southwest. UC Cooperative Extension irrigation specialist Khaled Bali believes sunflowers may be an ideal crop for the state's most punishing agricultural region.
California produces more than 90 percent of the country's hybrid sunflower planting seed, which is shipped around the nation and world. The seed is used to grow sunflower seeds for a healthy snack or salad topper, and for seeds that are expressed into sunflower oil, valued for its clean taste and polyunsaturated fat.
Most California seed is produced on about 50,000 acres in the Sacramento Valley. But the plant's low water use and early maturity hold promise for production in Southern California's low desert.
Bali's research began two years ago with 1,800 plots of sunflowers, nearly 300 different genotypes, at the UC Desert Research and Extension Center in Holtville. All plants were well-watered for four weeks before drought treatment started. In 2016, the trial plots were irrigated at 60 percent of the area's ETo (the full amount of water used by well-irrigated, mowed grass in that environment), and at 100 percent.
“Sunflower is a California native species grown as a hybrid seed crop,” Bali said. “With limited water, we wanted to look at varieties that tolerate drought and stress.”
That year, Bali found significant variation in yield across the varieties, but no difference between plots that received 60 percent of ETo and 100 percent
“I've been doing deficit irrigation for a long time,” Bali said. “I never expected that.”
For the 2017 season, the 60 percent ETo plots were dropped to 10 percent to better understand the implications of severe drought on the sunflower cultivars.
“The emphasis in 2017 was to intensify our drought treatment, giving less water earlier and to quantify the genotypes' drought avoidance strategy by digging up roots and using computer image analysis to determine root traits,” Bali said.
Bali attributes the sunflower crop's low water needs to its deep tap root and crop production timing. Sunflower in the low desert may be planted from January to February, and harvested in May and June.
“Sunflower water needs are relatively low since they are harvested before the hottest part of the summer,” Bali said.
His research is continuing in 2018.
A new UC publication, Sunflower Hybrid Seed Production in California, is now under review and is expected to be available to producers in fall 2018. Written by UC Cooperative Extension advisor Rachael Long and colleagues, including Bali, the publication outlines crop production standards, land preparation, fertilization, pest management, harvesting and more.
Long said sunflowers are favored for crop rotations because they help in long-term management of weeds and diseases, the plants add biomass to the soil after harvest, and they are a profitable specialty field crop.
Read more about California sunflowers in a Green Blog post by Rachael Long, Sunflower seeds are boosting California's ag economy.
The strawberry industry ended a long good-bye to methyl bromide in 2016. The fumigant had been used for decades to kill a wide range of soil-borne pathogens, weed seeds and insects, permitting the California strawberry industry to flourish. Scientists determined it was an ozone-depleting chemical in 1991, but its phase-out was delayed for years because of lack of equally effective alternatives.
Strawberry farmers now use a combination of approaches, including fumigation with other chemicals, soil oxygen deprivation, biofumigants, and beneficial microbes that improve soil biology. A greater arsenal is needed.
“Growers have three or four chemical alternatives, some are used alone and others in various combinations,” said UC Cooperative Extension advisor Surendra Dara. “Now, certain minerals, beneficial microbes and biostimulants are becoming available to enhance plant's natural defenses and improve strawberry growth, yield and health in an era without methyl bromide.”
Dara conducts research and advises strawberry and vegetable growers in the Central Coast counties of San Luis Obispo and Santa Barbara. Each year he holds a field day that attracts nearly 200 farmers, pest control advisers and representatives of allied industries to Manzanita Berry Farms outside Santa Maria. The agenda for the May 9 event included preliminary results of trials studying a number of commercially available and soon-to-be available biological and synthetic amendments to improve strawberry plant health, berry quality and yield.
Dara was ill, so Manzanita Farm owner Dave Peck reviewed the handout prepared by Dara for the field day. Manzanita Farms is one of two sites where Dara is testing products in replicated plots. Other studies are conducted in strawberries grown at the Shafter Research Station, a privately managed agricultural research facility in Kern County.
Several products resulted in increased marketable yield of strawberries during the February 2018 to April 2018 study period. See the preliminary results here. Data collection will continue through the end of the strawberry season.
“A challenge was that many people did not have complete faith in biologicals a few years ago,” Dara said. “By conducting multiple studies year after year, we are able to generate critical data that is useful for the farmers as well as companies that produce biologicals. By using different application strategies and rates, and a combination of techniques - as appropriate for their situations - farmers can engage in sustainable strawberry production.”
When San Juan Bautista resident Michael Cent was looking for ways to rehabilitate a large backyard pasture infested with invasive foxtail weeds, he called Devii Rao, the UC Cooperative Extension range and natural resources advisor in San Benito County.
Though Rao works mainly with large, commercial producers, she was intrigued by Cent's well thought out plans to replace foxtail with more desirable plants using sustainable practices. She paid him a visit.
Behind the home sits a two-acre fenced pasture where previous owners grazed llamas and ran horses. The picturesque setting adjoins San Juan Creek and frames a panorama of farm fields and the Diablo Mountain Range. But the tableau was spoiled by fence-to-fence foxtails, an exotic plant that hails from the Mediterranean, offers poor forage value and presents nuisance characteristics.
“The seed heads get stuck in the eyes, ears and noses of livestock and pets,” Rao said. “Foxtail is an annual grass that is difficult to control, but that didn't stop Michael Cent from trying.”
Cent is a pharmacist and self-described plant nerd.
“He turned his foxtail problem into a science project,” Rao said.
As a pharmacist, Cent said he is technically a chemist. “When you look at botany as chemistry, if you drill down into all the chemical reactions going on, it's amazing.”
Cent tested the soil Ph and nutrients. He identified 12 plants that would thrive under his pasture conditions and potentially out-compete the foxtails.
“In my research, much of what I see is not native,” Cent said. “My expectations to plant only natives have tempered. It's good to do within reason, but if a benefit of a non-native species outweighs a lesser advantage of being native, I'll go with the non-native species.”
Cent borrowed a tractor to break up the soil and reseeded by hand with his chosen grass and broad leaf plants. He kept detailed notes.
- Birdsfoot trefoil grew a dense carpet that choked out everything.
- Crimson clover germinated and grew quickly early in the season, but didn't do as well as anticipated.
- Harding grass was seeded specifically to out-compete the bristly ox-tongue, another undesirable plant.
- Chicory has a deep taproot, which helps it survive the dry season.
- Oxalis has come in like gangbusters, even though it wasn't seeded.
At first Cent regularly mowed the pasture to keep down the foxtails, but when the job became forbidding, he contracted with a company to bring in goats to aid control.
After four years of effort to overcome foxtail with grazing goats and seeding plants, Cent has come to a realization.
“I thought I could set it in motion and it would take care of itself,” Cent said. “But it's going to take a sustained effort.”
What drives Cent's devotion to rehabilitating a pasture with extensive plant research and management? The miracle of life, he said.
“The marvel of putting a seed in the ground, managing it and seeing what becomes of it. It's fascinating,” Cent said.
As sorghum plants cope with drought conditions, the plants' roots and adjoining microbial communities are communicating in a chemical language that appears to improve the plants' chances under water stress.
“It's amazing,” said Peggy Lemaux, UC Cooperative Extension specialist. “We know there are lots of microbes in the soil and, for the most part, ones in the surrounding soil stayed the same under drought conditions. We only saw changes in those microbes closely associated with the roots.”
The role of drought in restructuring the root microbiome was the first published discovery to come out of a sweeping drought research project underway since 2015 in the fields at UC Kearney Research and Extension Center in Parlier. The five-year study, funded with a $12.3 million grant from the Department of Energy, aims to tease out the genetics of drought tolerance in sorghum and its associated microbes. Using sorghum as a model, scientists hope the research will help them understand and improve drought tolerance in other crops as well.
The new research results from the lab of USDA's Devin Coleman-Derr at UC Berkeley, published April 16, 2018, in the Proceedings of the National Academy of Sciences, document the fate of microbes associated with sorghum roots under three distinct irrigation regimens. Because the San Joaquin Valley generally sees no rain during the growing season, it is the ideal place to mimic drought conditions by withholding irrigation water.
All plots received a pre-plant irrigation to initiate growth. In the control plots, sorghum was irrigated normally, with weekly watering through the season. In the plot simulating pre-flowering drought stress, the plants received no additional water until flowering, about halfway through the season. The third treatment was watered normally until it flowered, and then water was cut off for the rest of the season.
Beginning when the plants emerged, the scientists collected samples from each plot on the same day and time each week for 17 weeks. In a mini, in-field laboratory, roots, rhizosphere (zone surrounding the root), leaves and soil samples from 10 plants in each plot were immediately frozen and transported to Berkeley, where they were disseminated to collaborators, who investigated the plant and microbial responses at the molecular level.
“When a sorghum plant is subjected to drought, it starts sloughing off metabolites, nutrients and amino acids from the roots. The compounds appear to communicate to the neighboring microbial community that the plant is under stress,” Lemaux said. “That selects out a certain population of microbes. Certain types of microbes increase, others go away. When you add water back, the microbial community returns to its pre-drought population in just a few days.”
The researchers cultured two specific microbes that were enriched in the rootzone under drought conditions. They coated sorghum seeds with the microbes and planted them under drought conditions in a growth chamber. This treatment encouraged the plant to grow more roots.
“The microbes appear to improve plant growth during drought,” Lemaux said. “Those microbes appear to be helping plants survive drought. We didn't know that was happening before we got these results.”
Lemaux said the research might lead to future field use of the research breakthrough.
“A lot of companies are interested in the microbiome,” she said. “Some are already selling microbes to coat seeds.”