Posts Tagged: Oneto

Poison Oak: Leaves of Three, Let Them Be

Poison oak is a common native plant in California, growing everywhere from oak woodlands to urban...

Officials release new weevil to battle yellow starthistle

In April 2021, scientists released weevils from the Mediterranean region of Europe at the Bureau of Land Management Magnolia Ranch day-use area in El Dorado County to join the battle against yellow starthistle. Yellow starthistle rosette weevil is a newly approved natural enemy of yellow starthistle, which was introduced in California more than 150 years ago and, with no natural enemies in its new location, became one of the state's most harmful weeds, infesting nearly 15 million acres.

In California, yellow starthistle can grow to shoulder height, forming massive, thorny patches that block hiking trails, crowd out native plants and present a wildfire danger. The plant is toxic to horses and its flowers are encircled by inch-long sharp spines that can pierce the eyes of grazing animals.

UC Cooperative Extension has worked for decades with landowners to manage yellow starthistle-invested land.

“Over the years, we have developed effective control strategies for yellow starthistle – including well-timed mowing, grazing, hand pulling, burning, cultivation and herbicide application,” said Scott Oneto, UC Cooperative Extension natural resources advisor in El Dorado County. “But these treatments are rarely implemented on a scale large enough to combat our enormous starthistle infestations.”

Efforts to introduce natural enemies from yellow starthistle's home range began in the 1960s. Several species were released to attack starthistle flower heads. These insects lay eggs, hatch and feed on developing seeds, reducing seed production.

“Although the flower head insects sometimes attack high proportions of flowers, yellow starthistle is a very prolific seed producer with an individual plant producing as much as 100,000 seeds,” Oneto said. “Even if the insects reduce seed production by 50%, that still leaves a lot of seeds.”

The newly introduced yellow starthistle rosette weevil, first collected in Turkey as a prospective biocontrol agent in 1984, attacks the plant at the base. Since 2001, United States Department of Agriculture research entomologist Lincoln Smith has studied the insect at the USDA Agricultural Research Service laboratory in Albany.

“Larvae of the weevil develop and feed inside the root crown during spring, adults emerge in June, and then they spend the rest of the year hiding,” Smith said. “There is only one generation per year, so populations will grow slowly, which will gradually reduce yellow starthistle populations.”

The weevil presents no risk to other plants in California except bachelor's buttons, which is an introduced plant from Europe, but not considered a noxious weed. Successful biological control with the weevil is expected to reduce yellow starthistle, but not completely eliminate the weed.

This was the second release of the beneficial insect in North America. The first release occurred in Solano County in April 2020.

Bureau of Land Management and University of California Cooperative Extension researchers will be monitoring the Magnolia Ranch site intensively over the next several years to determine the rate of rosette weevil reproduction and efficacy at feeding on yellow starthistle.

For more information, see A New Warrior Released in the Battle to Control Yellow Starthistle by Scott Oneto on the UC Weed Science blog.

Pokeweed: A Growing Weed Problem

American pokeweed is a large weedy shrub also known as pokeberry, American nightshade, poke salad,...

Invasive Spotlight: Brooms

Brooms are shrubs which were originally planted in California as ornamentals and for erosion...

Rancher wisdom can be improved with science

When California was part of the Wild West, it took a certain amount of guesswork to move cattle from their home range to summer pastures while making sure sufficient forage was left behind to hold the cattle over till fall rainfall spurred new growth.

“Ranchers eyeballed it,” said Theresa Becchetti, UC Cooperative Extension livestock and natural resources advisor. “In time, second-, third-, and fourth-generation ranchers got pretty good at deciding, but UC Cooperative Extension introduced a more scientific approach.”

In the spring of 1936, the USDA Forest Services began measuring ungrazed forage at the San Joaquin Experimental Range in Madera County. The project continues today as a joint effort of UC Cooperative Extension and the USDA Natural Resources Conservation Service.

Sixteen years later, just after the UC Hopland Research and Extension Center was established on Mendocino County rangeland in 1951, another study began; and in the early 1980s, scientists at the UC Sierra Foothills Research and Extension Center in Browns Valley commenced a similar long-term study.

As scientists learned of the multiple factors impacting forage production across the Coast Range and Sierra Nevada foothills, some 70 research sites were identified – most on private land - and consistently monitored. The results show that there is much more to understanding forage growth than looking at a rain gauge.

Above, watch a full season of rangeland forage growth in one minute. UC Cooperative Extension rangeland and natural resources advisor Royce Larsen set up a camera to capture images of the daily grass growth on Pozo Peak in San Luis Obispo County.

While high annual rainfall usually results in high forage production and low annual rainfall generally results in low annual production, there are exceptions. It all depends on the timing of the rainfall.

During the devastating drought of 2011-2016, Becchetti noticed forage production didn't mirror the drought damage to state water resources and mountain forests.

“It was interesting,” said Becchetti. “In a lot of my plots, forage would be close to normal. We got rain when the soil was warming up. If we get rain in the late fall or winter, there is no grass production because it's too cool. If rains come when the temperatures warmed up, the grass takes off.”

The expected variation from climate change is another factor that encourages UCCE scientists to conduct routine forage monitoring.

“When I started 11 years ago, we had some good production years; we had poor years, a couple of normal years,” Becchetti said. “Monitoring is giving us a better snapshot that all of us can use to see the impact of climate change on forage production.”

To develop an accurate picture of forage growth, the research locations are fenced or caged to keep out grazing animals. Grass and forbs within one square foot of the exclosure is clipped to the ground. The vegetation is dried, weighed and the figures logged in a database.

Long-term production data are particularly valuable for the three research stations because daily weather data that are also collected there can be used to determine the effects of rainfall and temperature on annual forage productivity.

Year-to-year variability at the Hopland research site ranged from 900 pounds of forage per acre in the poorest year, up to a 3,500 pounds per acre bounty when conditions were just right. Average annual production at Hopland is 2,399 pounds per acre. At the Sierra Foothill Research and Extension Center, annual forage ranged from a low of 1,071 per acre up to 4,696 pounds per acre. The average annual production there is 2,971 per acre.

 “There is no way we could represent the exact forage production across the state, but this does allow us to come up with a percent either below or above normal for a particular area,” Becchetti said.

The monitoring research conducted by UCCE scientists are important to provide guidance to county agricultural commissioners and local Farm Service Agencies.

“If you think about it, so many of our ag commodities are based on weight or volume,” said Scott Oneto, UCCE rangeland and natural resources advisor in El Dorado, Tuolumne, Calaveras and Amador counties, where annual monitoring has been conducted for 25 years. “But annual rangelands are so different when it comes to figuring out whether a given year is average, above average or below average. And when crop insurance is involved, it makes it very difficult for ag commissioners to declare a loss if they don't know what the loss is or if there even was one.”

Becchetti, along with 14 current and former UCCE colleagues, wrote a 12-page review of UCCE's ongoing range forage production study, which includes average production for many of the study sites. ANR Publication 8018 is available for free download from the UC ANR publication catalog.

Read more