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UC scientist studies an alternative to burning old trees when replacing an orchard

When preparing to replant an orchard, farmers typically push together the old trees and burn them. UCCE advisor Brent Holtz is studying alternatives.
When almond orchards are about 25 years old, farmers must pull out the trees and plant new ones to maintain quality and yield. Typically, the old trees are pushed out and burned or ground up and hauled to a co-generation plant. However, UC Cooperative Extension advisor Brent Holtz believes there may be a better way.

Holtz has been pioneer in ag burn alternatives throughout his 26-year-career with UCCE, and going back still further on his family almond farm near Modesto. Beginning in the early 1990s, Holtz and his father experimented with chipping almond prunings instead of burning them, long before air quality regulations required wide implementation of the practice.

When Holtz heard a four-acre stone fruit orchard was slated for removal at the UC Kearney Agricultural Research and Extension Center in Parlier seven years ago, he took the opportunity to study the impact of grinding up and incorporating the whole trees before planting a new orchard.

“When an orchard is pushed out, there is about 100 tons per acre of organic matter that is taken out of the system,” Holtz said. “My previous research showed positive results from organic matter. Our San Joaquin Valley soils are typically critically low in organic matter. Why remove it if it is good for the soil?”

A local company was contracted to grind up and incorporate the trees using an Iron Wolf, essentially a 50-ton rototiller, in selected research plots. (See video below.) At first, Holtz was concerned that the Iron Wolf left “firewood-sized” chucks of wood in the plots, pieces much larger than he had studied before in his wood chipping research. But the worry turned out to be unfounded.

In comparison plots, trees were pushed together and burned. The ashes later were spread out on the soil. All the plots were fertilized at the normal rate.

Over the years, Holtz has compared laboratory analyses of the nutrients available to the trees in the soil and nutrients in the leaves. Initially, the burn treatments had more nutrients available. The second year, nutrient availability was about equal. Leaf analyses in the third year began to show a higher level of nutrients in the leaves of trees growing in the area where old trees had been ground up and incorporated. In the fifth and sixth years, Holtz didn't see any differences in growth, but data suggests slightly higher yields where the trees were ground up.

“A lot of growers feared if we added that much carbon to the soil, the microbes breaking down the organic matter would tie up nitrogen and the trees would be stunted,” Holtz said. “But the research results suggest that the trees will do just as well or better in the presence of the additional organic matter.”

One potential barrier to grinding up old trees is the cost. Holtz said the Iron Wolf treatment cost $800 per acre and it is not readily available in the San Joaquin Valley. Burning is nearly cost-free for the farmer, but contributes to air pollution and is highly regulated.

Another option for almond farmers preparing to remove an orchard and replant is employing a large tub grinder, which leaves much finer particles of wood than the Iron Wolf, is more readily available but more expensive. Holtz said he hopes that growers in the future will receive incentives to grind up their orchards and incorporate the wood chips into their soils before they plant a second- or third-generation orchard.

“I'm trying to find growers who would be interested in trying this approach to conduct on-farm research,” Holtz said.


In the video below, the Iron Wolf grinds up whole trees and incorporates the organic matter into the soil:

An initiative to enhance competitive and sustainable food systems is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.

Author: Jeannette Warnert

Posted on Tuesday, January 27, 2015 at 8:16 AM
Tags: air quality (1), almonds (3), Brent Holtz (1), burn (1)

Air pollution is ravaging what’s left of California’s native coastal sage scrubland

Coastal sage scrub near Lake Skinner in Riverside County, an area of relatively low nitrogen deposition.
Before Americans of European descent began actively farming and developing the beautiful, temperate California coast, vast stretches from San Francisco to the Mexican border were covered with a low-growing, aromatic plant community called coastal sage scrub. The ecosystem supported an array of seasonal wildflowers, such as California poppy, lupins, wild onions and sego lilies.

Because of its gentle topography and proximity to coastal cities, however, two-thirds of the coastal sage scrubland has already been converted to housing or farming, said Edith Allen, UC Cooperative Extension specialist in the Department of Botany and Plant Sciences at UC Riverside. The remaining coastal sage scrub is threatened by an invasion of exotic species and nitrogen deposition.

“Nitrogen deposition is caused by nitrogen oxide emissions from cars and industry. In addition, another plant fertilizer, ammonia, is emitted from agriculture and livestock operations,” Allen said. “The airborne emissions eventually settle on the soil surface, throwing the fragile coastal sage ecosystem out of balance, even 100 miles or more away from the emission sources.”

The combined deposition of nitrate and ammonia is up to 30 kilograms per hectare per year in the Los Angeles air basin. In contrast, in areas without the basin's air quality problems, about 2 kilograms are deposited per hectare each year.

“Growers fertilize small grain fields with 30 kilograms per hectare, so this represents a substantial nitrogen input,” Allen said.

Further compromising the coastal sage scrubland, grass species from the Mediterranean have been accidentally introduced into the ecosystem by activities associated with a booming agriculture industry, population growth, grazing and road building. The high nitrogen favors these exotic annual grasses.

“We've made a bad problem worse,” Allen said. “The exotic grasses are able to take up nitrogen at a faster rate, grow faster than native plants and displace them.”

In recent years, Allen worked with graduate students Robert Cox and Kristine Preston to understand vegetation-type conversion rate and recovery in coastal sage scrublands in western Riverside County. They compared information gathered by the Forest Service 85 years ago with 2002 California Department of Fish and Wildlife maps updated to 2009 using Google Earth. The analysis included measures of climate, topography, vegetation, land use, nitrogen deposition and fire in 151 study sites.

Former coastal sage scrub converted to exotic annual grassland near Mt. Rubidoux, Riverside County, following frequent fire and high nitrogen deposition.
The research revealed that 34 percent of coastal sage scrubland in western Riverside County had been converted to exotic grassland between 1930 and 2009. The converted sites had higher nitrogen deposition, shallower slopes and were more often west-facing.

The analysis showed that 24 percent of the sites that were mapped as annual grassland in 1930 had recovered to coastal sage scrubland.

“In those parts of the county that did not receive much nitrogen, the native vegetation was able to recover,” Allen said. “Overall, the study shows that coastal sage scrubland conservation and restoration efforts are most likely to be successful on sites with low nitrogen deposition and low invasion of exotic grasses.”

For that reason, it only makes sense to try to restore coast sage scrub in areas where nitrogen deposition is low. For broader conservation, the best option is improving air quality.

This research determined that regions where nitrogen deposition is above the level of 11 kilograms per hectare per year will spontaneously convert to grassland.

“We have a value that can be used by regulatory agencies,” Allen said. “Right now, air pollution regulations aren't strong enough to protect the environment.”

Today, most passenger cars emit very low amounts of nitrogen oxides. The bigger problems in the Los Angeles Basin are diesel trucks and pollution generated in the ports of Los Angeles and Long Beach.

“Our population is growing. The volume in the ports is growing. As we come up with better, cleaner technologies, we're staying at the same pollution levels,” Allen said. “People need to realize that we will need lower nitrogen emission levels to protect our natural plant communities.”

The research was published last fall in the journal of Global Ecology and Conservation.

An initiative to maintain and enhance sustainable natural ecosystems security is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.

Posted on Friday, January 23, 2015 at 3:00 PM

Exotic mange found in California golden eagles

Golden eagle before treatment
Golden eagles in the western United States may be at risk of infestation by an exotic and possibly new species of mite that causes a fatal skin disease, according to an Emerging Infectious Diseases case report published in October 2014. 

Two adult golden eagles that were recovered in California between July and August 2013 were infested by a mite with morphologic features similar to those of Micnemidocoptes derooi, a species of mite seen only once, in an African palm swift in West Africa more than 40 years ago.

Both eagles had substantial feather loss and scabbing on the head, neck, and legs and near the cloaca. One of the raptors was found grounded and so ill the animal was euthanized. The other was live-trapped, rehabilitated, and eventually returned to the wild. (She underwent 8 months of recovery and rehabilitation at the California Raptor Center, a program of the UC Davis School of Veterinary Medicine. Read her story here.)

A third golden eagle, found in December the previous year in the same region as the others, was likely also infected by the Micnemidocoptes–like mite, according to the report. The bird had been struck by a car and died of its injuries.

In their report, the authors note that while wild raptors can sometimes become infested with mites, such debilitating mange in otherwise healthy animals is highly atypical.

“The severity and diffuse distribution of skin lesions of these eagles suggest a possible serious, unique outbreak,” they wrote. 

Additional golden eagles with suspicious feather loss have been spotted in California and Nevada since August 2013.

Ready for release
Dr. Michelle Hawkins is director of the California Raptor Center at the University of California-Davis School of Veterinary Medicine and one of the report's co-authors. Her team spent several months treating the golden eagle that was eventually healthy enough to be released. Dr. Hawkins said mites in the Knemidocoptinae subfamily typically infest a bird's non-feathered areas, such as its face, beak or legs. The mites on the golden eagles are unusual because they only affected the feathered areas.

Feather loss impacts an eagle's ability to maintain normal body temperature and may limit the animal's ability to obtain food, making it weak and susceptible to trauma. Severe mite infestation is unusual in birds, especially adult birds. No such infestation among golden eagles has been previously reported.

“It's all very strange,” Dr. Hawkins admitted. “It's not something that's been identified by any researchers that we're aware of at that point. This may be closely related to M derooi but has not been previously described.”

As for how this potentially novel species of mite arrived in the United States and is spreading, they are also mysteries. The entire life cycle of M derooi is reported to be spent on its host, so theoretically, transmission would require direct contact between birds. Dr. Hawkins supposes the mites could be passed along through an infested bird's nest, although additional research is needed in this and other areas involving this mite.

In the meantime, the California Department of Fish and Wildlife is asking residents to report golden eagles or other large birds with severe feather loss. Dr. Hawkins has written a paper on the clinical treatment of eagles with mange, which is expected to be published in the near future.

The article, “Knemidocoptic mange in wild golden eagles, California, USA,” is also available online.

This article originally appeared in JAVMA News by Scott Nolen.

Posted on Wednesday, January 21, 2015 at 9:27 AM

New online course helps PCAs manage pesticide resistance

New online course focuses on pesticide resistance.
Pesticide resistance is not a new subject, and researchers have been working for years on how to manage the problem. Resistance develops when the same type of pesticide is used repeatedly and frequently to control a pest. Every pest population contains individuals that vary genetically in some way; some vary in their susceptibility to being killed by a particular pesticide.

When a pesticide is applied, some individual insects or weeds are killed and others are not. The individuals that are not killed vary genetically from the ones that were killed, and when they reproduce, their offspring are also likely not to be susceptible to the pesticide. Over time, the population changes and you are left with the genetically resistant individuals as the majority of the population. Resistant pests can result in higher pesticide rates being applied and more frequent applications. We see resistance occurring in weeds, insects and pathogens.  

Pest control advisers and growers are often the first to see what is going on in the field. After a pesticide is applied, they may be the first to report back to researchers if the application was effective or not. If they see patterns of decreased susceptibility of a pest population to a pesticide that was previously effective at controlling the pest, they may conclude that resistance is occurring. Pesticide resistance is the topic of a new online course developed by UC IPM that can help PCAs and other licensed pesticide applicators recognize resistance when it is occurring, discover how it developed, apply practical methods of managing it and delay its occurrence.

The new online course covers resistance within the disciplines of plant pathology, entomology and weed science. It is based on a series of workshops on resistance management held in Davis, Fresno and at the UC Kearney Agricultural Research and Extension Center during the spring of 2014 presented by UC Cooperative Extension specialists Doug Gubler (Dept. of Plant Pathology, UC Davis.), Larry Godfrey (Dept. of Entomology and Nematology, UC Davis), Beth Grafton-Cardwell (Lindcove Research and Extension Center and UC Riverside Dept. of Entomology), and Kassim Al-Khatib (UC Statewide IPM Program).  

There are several mechanisms through which pests become resistant to pesticides. One mechanism common to all three disciplines is target site alteration, where the site a pesticide normally attacks is somehow altered and no longer allows a pesticide to bind and affect the pest. Metabolic resistance is another mechanism, where pests detoxify or break down the chemical before it can work.

Although some differences occur in delaying or managing resistance across the disciplines, the key is to try to avoid intensive applications of pesticides so as not to allow resistant pests to become the majority of the population. Good IPM practices can reduce the need for pesticide applications. Rotating chemicals with different modes of action can also help manage resistance.

For an in-depth look at pesticide resistance, check out the new course at This course has been approved for two continuing education units in the “Other” category from the Department of Pesticide Regulation.

Posted on Wednesday, January 14, 2015 at 8:58 AM
Tags: IPM (9), resistance (1)

Turkey vultures have peculiar nesting habits, study finds

A turkey vulture spreads its wings at Hopland. (Photo: Robert Keiffer)
Omnipresent and homely, turkey vultures are a native California wildlife species that doesn't get a lot of research attention.

But UC Cooperative Extension advisor Greg Giusti has found a surprising level of interest from the public in his Northern California research project about turkey vultures' nesting preferences in oak woodland.

“Animals with cute fuzzy faces are far more attractive in our culture,” said Giusti, a wildland ecology expert. “Turkey vultures have been overlooked. Very little is known about their biology and environmental needs.”

Giusti worked with Robert Keiffer, superintendent of the 5,300-acre UC Hopland Research and Extension Center in Mendocino County, to better understand the nesting habits of the red-faced scavengers.

In the study area, the researchers counted 417 trees in all; seven of them had suitable nesting elements for turkey vultures. They found that the vultures at the Hopland facility select large hollow trees – either dead or alive, either shaded or in the sun – to lay eggs and rear their young. The tree species in the study included blue oak, interior live oak, Oregon white oak and valley oak.

Turkey vulture nestlings deep inside a hollow tree at the UC Hopland Research and Extension Center.
The nesting trees were widely dispersed and ranged in diameter from 36 inches to 65 inches around at breast height. The nesting cavities are vertical tubes in the tree trunks that drop down as much as 13 feet from the entrance to the ground.

“This is very different from other large birds, like eagles and osprey, who build open cup nests high up in tall trees, which they may use for generations,” Giusti said.

After turkey vulture chicks hatch, the parents drop into the cavity five or six times a day to feed their young, Giusti said. How birds with a five-foot wingspan traverse a deep vertical tunnel is a mystery.

“They just shimmy up and down, I would imagine,” Giusti said. “We don't know how the young birds do it when they fledge. We've never witnessed the adult birds calling them out.”

Giusti said the scientists will continue to build on the turkey vulture nesting database they have started with results from this project. In the coming years, they hope to learn whether turkey vultures will re-use successful nesting sites and whether they may be found nesting in fallen logs or rock piles.

In the video clip below, a turkey vulture explores a possible nesting cavity at the UC Hopland REC.

An initiative to maintain and enhance sustainable natural ecosystems is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.

Posted on Friday, January 9, 2015 at 8:25 AM

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