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Posts Tagged: citrus

Climate change may reduce frost damage to orchard crops

Extreme cold can kill almond buds and flowers. Running sprinklers can warm the orchard to prevent frost damage. Photo by Allen Vizcarra

Irrigation water may ice some flowers, but help protect flowers in the upper canopy from frost damage. Photo by Allen Vizcarra

CalAgroClimate web tools help farmers prepare for frost events

A cold snap damaged almond blossoms across the Central Valley, resulting in more than $44 million in crop insurance claimsin late February 2018. A multi-day frost event wiped out roughly 75% of California's citrus crop and severely damaged avocados in January 2007. Frost can damage crops, impact growers' bottom lines and drive up food prices for consumers. With advance notice, farmers may be able to use heaters, wind machines, irrigation and other tactics to lessen some of the impacts of cold weather, such as damaging near-ripe citrus fruit or killing the bloom in almonds.  

CalAgroClimate is a new farmer-focused website that can help growers anticipate weather-related risks and make plans for taking defensive action. Growers and crop consultants can use CalAgroClimate's crop and location-specific tools and resources to help prepare for upcoming frost events. The website's tools can also support on-farm decisions for managing heat, crop development and pests. 

Future holds less frost

The risk of frost damage to crops and the need to prepare for that risk is top-of-mind for many farmers today, but will it always be so? To examine what climate change might mean for future frost risk, researchers at UC Davis, UC ANR and the USDA California Climate Hub conducted a study examining the incidence of temperatures below multiple “frost thresholds” during the months of critical development phases for three frost-sensitive California crops: almonds, avocados and navel oranges.

Severely frozen avocados may show brown water-soaked spots in the skin, gray areas in the flesh and may even crack or split. Frost-damaged fruit is unmarketable and will drop from the tree. Photo by Mary Lu Arpaia

The researchers found that even during the coldest winters and springs, the incidence of frost exposure declined under projected mid-21st century climate conditions by more than 50% for almonds and oranges, and by more than 75% for avocados. While farmers in 2050 will not find frost risk to completely be a worry of climates past, they will not have to contend with the same frost concerns that farmers face today.

Frost-damaged citrus
Beyond the obvious benefits of reduced risk of crop damages, additional benefits of reduced frost exposure include lower water use and energy costs associated with mitigation actions. Irrigation is a primary means of protecting crops from frost temperatures, and with fewer hours below freezing that means fewer hours of running water and using pumps. The authors of the future frost exposure study showed that growers may collectively save tens of thousands of acre feet of water and enjoy millions of dollars in energy savings.

Few aspects of climate change are considered “positives,” and although the warming winters and springs that result in reduced frost temperatures could also come with increased pest pressure, reduced chill accumulation and other challenges, the reduction in frost exposure is a silver lining.

However, until this frost-free future arrives, growers still need to be prepared to protect their orchards from frost. To assess frost risk for the next seven days for your location, check out the new interactive Frost Advisory Tool at CalAgroClimate.org.

Posted on Monday, January 23, 2023 at 1:20 PM
  • Author: Lauren E. Parker, USDA Climate Hub
  • Author: Tapan Pathak, UC Cooperative Extension specialist
Tags: almonds (64), avocados (6), CalAgroClimate (1), citrus (27), climate change (112), Tapan Pathak (11)
Focus Area Tags: Agriculture

UCCE researchers target sugar-feeding ants, a key to controlling citrus pests, disease

David Haviland sharing his research at the Argentine Ant and Citrus Pest Management Field Day in Redlands in October 2022. All photos by Saoimanu Sope.

Sugar-feeding ants protect pests that infect trees and damage the fruit they bear. Insecticides are often a go-to solution, but may kill beneficial insects in the process, too. Thankfully, Mark Hoddle, University of California Cooperative Extension entomologist and biological control specialist at UC Riverside, together with UCR colleagues in chemical engineering, developed a biodegradable hydrogel baiting system that targets ant populations, which protect sap-sucking pests from their natural enemies. Control of ants allows beneficial parasitoids and predators to greatly reduce pest populations.

Deciding to expand Hoddle's research was a “no-brainer” according to David Haviland, UC Cooperative Extension farm advisor in Kern County.

Haviland is investigating active ingredients that can be effectively used in hydrogel baiting systems. His research builds on Hoddle's use of alginate gels, also known as water beads, soaked in sugar water to control Argentine ants.

“What we're doing in California can benefit places like Florida, Texas, Mexico and beyond,” Haviland said.

A display of Argentine ants at the Argentine Ant and Citrus Pest Management Field Day in Redlands in October 2022.
Sugar-feeding ants are a universal problem as they interfere with biocontrol processes and promote diseases like huanglongbing, or citrus greening, because there are more vectors to spread disease-causing organisms between trees.

The Hoddle lab conducted two years of orchard research showing that when ants are controlled, the amount of citrus flush infested with Asian citrus psyllid (ACP), a mottled brown insect that vectors the pathogen causing citrus greening, decreases by 75%. Citrus flush refers to newly developed leaves.

“But benefits are not restricted to just ACP with Argentine ant control, as natural enemies destroy colonies of other sap-sucking pests too,” said Hoddle. “For example, citrus mealybug infestations on leaves were completely eliminated by natural enemies, 100% control, while densities of fruit infested by mealybugs were reduced by 50%.” 

The Hoddle lab's success inspired Haviland to consider how this approach will fare in different regions of the state where there are different crops, different pests and different ant species. 

Haviland has worked for many years on solid baits that are effective and affordable for ants that feed primarily on protein, like fire ants in almonds, but successful control measures for sugar-feeding ants that drink their food have been elusive.

“Therefore, we're using hydrogels to essentially turn a liquid bait into a solid, making it effective and commercially adoptable,” Haviland said. He and his team are assessing whether active ingredients that undoubtedly work against ants, like thiamethoxam, maintain their effects in a hydrogel system.

Unlike Hoddle's biodegradable alginate gels, Haviland is relying on acrylamide gels that are similar to the absorbing material you would find in a diaper. These gels are not organic, but are currently accessible on a commercial scale, and have been shown to be effective in wine grapes on the North Coast by a Cooperative Extension advisor in Napa County, Monica Cooper. Haviland's current research efforts are focused on citrus, table grapes and wine grapes in the San Joaquin Valley, and on lemons on the coast.

Hoddle's hydrogel baiting system uses alginate gels.
Haviland is experimenting with acrylamide gels.

The primary challenge now is navigating pesticide regulations and registration.

“This is cutting-edge research,” Haviland said, and manufacturer labels for the products being used need to be updated to include hydrogels as an approved use. This process takes time. Additionally, adding new product uses needs to make economic sense for the manufacturer.

Hoddle and Haviland's research can provide data for adding these methods to the product labels.

“If we can show that this tech works against lots of pests, lots of ant species, in lots of different crops across California, hopefully we'll achieve a critical mass of benefits that motivates product manufacturers to make modifications to their labels,” said Haviland.

Haviland is hopeful about the process, and said he believes that UC ANR is in a prime position to lead innovation for an issue that requires collaboration among specialists, advisors and the industry.

Posted on Monday, January 9, 2023 at 1:54 PM
Tags: ants (41), Argentine (1), bait (1), biocontrol (6), citrus (27), Haviland (1), Hoddle (1), hydrogel (1), innovation (2), Kern (1), pest (6), pesticide (1), Riverside (2), sugar (3)
Focus Area Tags: Innovation, Pest Management

Molecular Biologist Michelle Heck: Challenges of Citrus Greening Disease

If you grow citrus, you've no doubt heard of the invasive pest, Asian citrus psyllid, Diaphorina citri. ACP they call it. A native of...

Asian citrus psyllid nymphs and adults on stem and leaves of a citrus. (USDA-ARS Photo)
Asian citrus psyllid nymphs and adults on stem and leaves of a citrus. (USDA-ARS Photo)

Asian citrus psyllid nymphs and adults on stem and leaves of a citrus. (USDA-ARS Photo)

Posted on Friday, February 11, 2022 at 5:01 PM
Focus Area Tags: Agriculture, Economic Development, Environment, Innovation, Natural Resources, Pest Management, Yard & Garden

Cleaning the Tongue: A, B, C

So here you are, a honey bee seeking nectar from an unopened citrus blossom. And then your tongue (proboscis) becomes all sticky with pollen, nectar...

A honey bee takes a break and cleans her proboscis (tongue) after foraging on a citrus blossom. (Photo by Kathy Keatley Garvey)
A honey bee takes a break and cleans her proboscis (tongue) after foraging on a citrus blossom. (Photo by Kathy Keatley Garvey)

A honey bee takes a break and cleans her proboscis (tongue) after foraging on a citrus blossom. (Photo by Kathy Keatley Garvey)

Break over and time to get back to work! A worker bee and a mandarin blossom. (Photo by Kathy Keatley Garvey)
Break over and time to get back to work! A worker bee and a mandarin blossom. (Photo by Kathy Keatley Garvey)

Break over and time to get back to work! A worker bee and a mandarin blossom. (Photo by Kathy Keatley Garvey)

Posted on Wednesday, April 7, 2021 at 3:32 PM
Focus Area Tags: Agriculture, Environment, Food, Natural Resources

Asian citrus psyllid infected with huanglongbing disease found in Riverside citrus grove

The recent identification of an Asian citrus psyllid infected with huanglongbing disease in a Riverside commercial citrus grove isn't surprising, said UC Cooperative Extension specialist Monique Rivera in an interview with Brian German of AgNetWest.

"We've had positive trees removed here in Riverside and we're not that far from LA," Rivera said. "Eventually those two quarantine circles are likely to merge here in Southern California."

The two red-outlined areas show the ACP and HLB quarantine areas in Southern California. (Screen shot taken Aug. 13, 2020. For updated information, see https://ucanr.edu/sites/ACP/Distribution_of_ACP_in_California/)

Rivera said an HLB-infected ACP hasn't been found in Riverside commercial citrus before because CDFA is mainly responsible for sampling ACP in backyard trees. "They aren't looking directly or systematically at commercial groves," she said.

There are resources available for growers to test ACPs found in their citrus orchards. Growers can request PCR testing of ACP or plant samples from an accredited lab, such as the Citrus Pest Detection Program (CPDP) which is operated by the Central California Tristeza Eradication Agency. CDFA will also collect samples for analysis at no cost to the grower.

Posted on Thursday, August 13, 2020 at 10:55 AM
Focus Area Tags: Agriculture

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