California Naturalist
California Naturalist
California Naturalist
University of California
California Naturalist

ANR Green Blog

August 19th is National Honey Bee Day: Dr. Elina Niño reminds us to help honey bees cope with pests

National Honey Bee Day is celebrated on the third Saturday of every August. This year it falls on Saturday the 19th. If you use integrated pest management, or IPM, you are probably aware that it can solve pest problems and reduce the use of pesticides that harm beneficial insects, including honey bees. But did you know that it is also used to manage pests that live inside honey bee colonies? In this timely podcast below, Elina Niño, UC Cooperative Extension apiculture extension specialist, discusses the most serious pests of honey bees, how beekeepers manage them to keep their colonies alive, and what you can do to help bees survive these challenges.

https://soundcloud.com/ucipm/help-honey-bees-cope-with-pests

To read the full transcript of the audio, click here.

Successful IPM in honey bee colonies involves understanding honey bee pest biology, regularly monitoring for pests, and using a combination of different methods to control their damage.

Visit the following resources for more information

For beekeepers:

For all bee lovers:

Sources on the value of honey bees:

 

 

Posted on Thursday, August 17, 2017 at 9:14 AM

New dust sources resulting from a shrinking Salton Sea have negative ecological and health impacts

Salton Sea. Photo courtesy of NASA
UC Riverside study shows soils once submerged under the sea and airborne particulate matter are high in sodium and selenium

Scientists at UC Riverside investigating the composition of particulate matter (PM) and its sources at the Salton Sea have found that this shrinking lake in Southern California is exposing large areas of dry lakebed, called playa, that are acting as new dust sources with the potential to impact human health.

“Playas have a high potential to act as dust sources because playa surfaces often lack vegetation,” said Roya Bahreini, an associate professor of environmental sciences, who led the research project. “Dust emissions from playas increase airborne PM mass, which has been linked to cardiovascular disease, respiratory disease, and mortality.”

Study results appeared recently in Environmental Science and Technology.

Bahreini's team set out to test whether emissions from playas change the composition of PM10 (particulate matter with diameters up to 10 microns) near the Salton Sea. The team assessed the composition of playa soils (recently submerged underneath the Salton Sea), desert soils (located farther from the sea), and PM10 collected during August 2015 and February 2016.

They found that dust sources contributed to about 45 percent of PM10 at the Salton Sea during the sampling period while playa emissions contributed to about 10 percent. Further, they found that playa emissions significantly increased the sodium content of PM10.

Roya Bahreini is an associate professor of environmental sciences at UC Riverside.
“Increase in the sodium content of PM10 can affect the ecosystem when the sodium-rich particles deposit downwind and change the natural balance for soils and agricultural lands or when these particles form clouds,” Bahreini said. “Currently, the primary concern for PM emissions from playa is the contribution to total concentration of PM10, which regardless of composition, is an irritant and can have negative respiratory effects.”

Her team also found that playa soils and PM10 are significantly enriched in selenium relative to desert soils.

Bahreini explained that selenium can be a driver of aquatic and avian toxicity. “Additionally, higher selenium enrichments in PM10 during summertime suggest that selenium volatilization from the playa may become an important factor controlling the selenium budget in the area as more playa gets exposed,” she said.

Alexander L. Frie, a graduate student in environmental sciences and the first author of the research paper, urges that the Salton Sea be paid close attention since, although it is widely considered a large ecological disaster, with no serious monitoring and remediation efforts the sea may also create a human health crisis for the surrounding area.

Alexander L. Frie, a graduate student in environmental sciences and the first author of the research paper, at the sampling site.
“Although our results indicate playa emission may not be especially toxic when compared to other dust particles, increased emissions from a shrinking sea will reduce the quality of life of the residents within the Imperial Valley and other downwind regions,” he said.

Samantha C. Ying, an assistant professor of environmental sciences and a coauthor on the paper, stresses that monitoring the increase in dust sources over time is necessary to quantify its contribution to local health problems.

“Our study shows that the shrinking Salton Sea is contributing to dust sources in the region,” she said. “Even considering just the small area of playa that is exposed now, the contributions are significant.”

Another concern the researchers point out is that water that is currently diverted from the Colorado River and directed into the Salton Sea is scheduled to end before 2018. The resultant decrease of inflow into the sea will likely cause a decline in water level, exposing more playa, and therefore emitting more dust.

“With more playa being exposed, we expect total PM10 concentrations to increase and human exposure to these particles in downwind areas will also increase,” Bahreini said. “Therefore implementing any project, for example, creating shallow water pools over the playa, that limits formation of salt crusts on the playa will be valuable.”

Bahreini, Frie and Ying were joined in the study by Justin H. Dingle, a graduate student in Bahreini's lab.

The study was funded by UCR Regents' Faculty Development Award, USDA National Institute of Food and Agriculture, a UCR Provost Research Fellowship, the U.S. Geological Survey and ANR's California Institute for Water Resources.

Read more: 

KPBS, David Wagner New Study Traces Airborne Dust Back to Shrinking Salton Sea

The Desert Sun, Ian James Studying dust around the Salton Sea, scientists find initial answers

Palm Desert Patch The Hidden, Potentially Deadly, Dangers of The Salton Sea

 

 

Posted on Tuesday, August 8, 2017 at 10:36 AM
  • Author: Iqbal Pittalwala

How to check your citrus trees for a deadly disease and the pest that spreads it

There is no known treatment for huanglongbing, which kills citrus trees.

The incurable citrus tree disease huanglongbing, or HLB, has been detected in Los Angeles and Orange counties and most recently in Riverside. The citrus disease is spread from tree to tree by Asian citrus psyllids, the insects that move the bacteria that cause huanglongbing.

Citrus trees infected with huanglongbing develop mottled leaves and produce fruit that is misshapen, stays green and tastes bitter. There is no known treatment for the disease, which usually kills the tree within three to five years, according to UC Cooperative Extension specialist Beth Grafton-Cardwell.

Huanglongbing causes blotchy yellow mottling that is not the same on both sides of the leaf
Huanglongbing, which is also known as citrus greening, has already devastated the citrus industries in Florida, Georgia, Louisiana, South Carolina and Texas.

You can help prevent this disease from destroying California's citrus as well as your own trees.

Look for yellowed leaves on citrus trees. Nutritional deficiencies can also cause citrus trees to have yellow leaves so it is important to know the difference. Nutrient deficiency causes a similar pattern of yellowing on both sides of the leaf. HLB causes blotchy yellow mottling and is not the same on both sides of the leaf.

To identify the Asian citrus psyllid and the disease symptoms of HLB, see the fact sheets, videos in English and Spanish and other resources at http://ucanr.edu/acp.

If you see any trees that display symptoms of huanglongbing, contact your local agriculture commissioner.

To learn about the latest research, visit UC ANR's new Science for Citrus Health website at http://ucanr.edu/sites/scienceforcitrushealth.

More resources on Asian citrus psyllids and huanglongbing:

 

Posted on Friday, July 28, 2017 at 2:04 PM

UC has boots on the ground in an unrelenting search for Asian citrus psyllid

With two magnifying loops around her neck and a truck stocked with vials and tools for insect collection, Joanne O'Sullivan scouts Ventura County citrus orchards every day. She walks the perimeter, examining newly emerging leaves and tapping branches with a PVC wand to bat pests onto her clipboard.

O'Sullivan is one of four scouts hired and trained by UC Agriculture and Natural Resources scientists to carefully and continuously monitor citrus orchards for Asian citrus psyllid, an invasive pest in California that can spread the devastating huanglongbing disease.

Joanne O'Sullivan is one of the scouts hired by UC to search for and collect Asian citrus psyllids.

In Florida, where the pest was left unchecked when it first invaded citrus growing regions, the disease swept through the state. Citrus production in the Sunshine State plummeted 60 percent in 15 years.

“We don't want to let that happen here,” said Beth Grafton-Cardwell, UC Cooperative Extension entomology specialist. Grafton-Cardwell hired O'Sullivan and her colleagues who monitor citrus in San Diego, Imperial, Riverside and San Bernardino counties to scour dozens of orchards to document how treatments to control ACP are working. Next year scouts will be added in Tulare and Kern counties.

When ACP are found, they are carefully bottled and sent to the lab to determine whether they carry the bacterium that causes huanglongbing disease.

O'Sullivan taps branches with a PVC wand to knock off insects.

The expansive ACP monitoring effort is funded by a $1.45 million multi-agency coordination grant from the USDA. The project funds promising tools and long-term solutions to reduce the spread of huanglongbing. Led by Neil McRoberts, a professor of plant pathology at UC Davis, the grant also provides funds for two other activities. 

One is a collaboration with California Citrus Mutual to offer free citrus tree removal to homeowners in areas where HLB is known to occur. The second is modeling data from the CDFA HLB survey program, in which psyllids and symptomatic plant tissue are tested for the bacteria. Trees may have the disease but not show symptoms, so testing the psyllids is a more effective way to find infected trees. The modeling work will improve the ability to predict the locations of infected trees.

However, the main thrust is monitoring citrus treatments and their impacts on the ACP population with a team of scouts. A mix of conventional and organic farmers and growers who use biological integrated pest management programs to manage their orchards were recruited for the project. The farmers make ACP treatment decisions informed by research results that show the best treatments and timing.

“Most growers are coordinating their treatments to get a bigger bang for their buck,” Grafton-Cardwell said.

If she finds ACP, O'Sullivan places them in vials to be sent to a lab for testing to determine whether they are carrying the bacterium that causes huanglongbing disease.

With just six months of data, the monitoring program has already yielded important information about Asian citrus psyllid.

“We're seeing more psyllids on the borders than the centers of groves,” Grafton-Cardwell said. “And so eventually, we will make recommendations that at certain times of year or when populations are low, the grower will only need to spray the borders of the grove."

This will reduce costs and the impact of pesticides on natural enemies.

"The early data have also revealed which chemicals are the most effective for psyllid control. We've found that organic growers need to be more aggressive in the frequency of treatments, because the organic insecticides are not as effective as conventional insecticides," she said.

At 8 of the 49 Ventura County ranches in the project, yellow sticky traps were placed in trees to monitor for ACP's natural enemies, including lady bugs, green lacewings, and Tamorixia radiata, tiny wasps from Pakistan that were released in California to battle ACP.

O'Sullivan spends her days looking for ACP and rooting for natural enemies that can help control them.

When O'Sullivan sees one of the natural enemies at work in the field, she pauses to observe the process.

“Sometimes I'll see a lacewing munching on an ACP and I'll say, ‘Go man, go!'” O'Sullivan said.

Posted on Friday, July 28, 2017 at 8:19 AM

UC scientist gives orchards a whole new color scheme

For centuries, farmers have used all the colors of the rainbow to assess their orchards: The bright pink of blossoms in springtime, the vibrant green of heathy leaves, the red blush on fruit ready to harvest.

However, there are wavelengths beyond what a human eye can see that also provide valuable information about the crop – including tree vigor, plant stress, water use and fertilizer needs.

UC Cooperative Extension agricultural engineering advisor Ali Pourreza is peering into these previously invisible colorations to create a virtual orchard that will quickly, easily and inexpensively allow farmers and scientists to manage orchards for optimum production.

To develop his first virtual orchards, Pourreza launched a camera-equipped drone over an orchard at the UC Kearney Agricultural Research and Extension Center in Parlier. As the drone flies over the trees, it snaps thousands of photos and, using photogrammetry and software that stiches the images together, makes a three-dimensional point cloud model of the orchard.

A computer program can make colors that are invisible to the human eye – such as near infrared, red edge and ultraviolet – into imagery that illuminates key crop health indicators. Near infrared indicates the amount of healthy foliage, plant vigor and crop type. If the trees have low near infrared values, it means the plants are under stress. Red edge indicates plant stress and nitrogen content. High red edge values indicate nitrogen stress and low water content in plant tissues.

UCCE ag engineer Ali Pourreza views the virtual orchard on his computer.

Patrick Brown, a pomology professor at UC Davis, is planning to use the virtual orchard to map nitrogen use in citrus.

“We are currently working on developing models to help growers determine their fertilization demands and have been contrasting the results from real orchards with the virtual orchard,” Brown said. “We have already utilized the approach to contrast the estimates of tree growth and yield with whole tree excavations and harvests to help validate the virtual approach and provide a more accurate estimate of tree nitrogen demand.”

Ultimately, Brown hopes to develop a way for growers to rapidly and cheaply estimate the nitrogen demand of their orchards, monitor the status of their orchards and manage nitrogen fertilizer applications.

The drone hovers over an orchard at the UC Kearney Agricultural Research and Extension Center.

In addition to the color variations brought to light by the virtual orchard, the system provides detailed data on other aspects of the crop development.

“We can learn canopy height and width, the spacing between the trees, total leaf area, canopy density and the amount of shaded area in the orchard,” Poureza said.

This data is of interest to scientists studying plant development, soil health and irrigation.

For example, UCCE agricultural water management specialist Daniele Zaccaria is researching the impact of soil-water salinity on water use by pistachio trees in the San Joaquin Valley.

“In our on-going research study we are characterizing the functional relationships between soil-water salinity, canopy size and density and evapotranspiration of pistachio trees through the light interception by the canopy,” Zaccaria said. “We plan to work with Ali to see how the virtual orchard approach can represent that and simulate the physical process of soil evaporation and tree transpiration as a result of different canopy sizes and densities intercepting different amounts of solar radiation.”

Zaccaria said he also plans to deploy a similar approach to understand how different canopy sizes, planting densities and row orientations found in commercial citrus orchards in the San Joaquin Valley – from navel oranges, to mandarins and lemons – can affect the citrus water demand and use.

In addition to the rich data that scientists can glean from the virtual technology, Pourreza envisions many applications of this technology for farmers, including yield forecasting, blossom mapping, variable pesticide application and robotic harvesting.

Ali Pourreza with the drone he uses to create virtual orchards.
 
View a video on YouTube produced by the scientist, Ali Pourreza. The video shows images of the virtual orchard.
Posted on Tuesday, July 25, 2017 at 11:10 AM
Tags: Ali Pourreza (1), drone (1), virtual orchard (1)

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