Posts Tagged: Hoddle

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

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.

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.

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.

The scent that could save California’s avocados

Scientists search for pheromone to disrupt insect mating

UC Riverside scientists are on the hunt for a chemical that disrupts “evil” weevils' mating and could prevent them from destroying California's supply of avocados.

Avocado weevils, small beetles with long snouts, drill through fruit to lay eggs. The weevil grubs or larvae bore into avocado seeds to feed, rendering everyone's favorite toast topping inedible.

“They're extremely hard to control because they spend most of their time deep inside the fruit, where they're very well protected from insecticides and natural enemies,” said UCR researcher Mark Hoddle, a UC Cooperative Extension entomology specialist.

Not only are the insects reclusive, they are also understudied, making information about them hard to come by. “All books on avocado pest management will tell you these weevils are bad. They're well recognized, serious pests of avocados, but we know practically nothing about them,” Hoddle said.

One strategy for controlling pests is to introduce other insects that feed on them. However, that is unlikely to work in this case. “Natural enemies of these weevils seem to be extremely rare in areas where this pest is native,” Hoddle said.

To combat avocado weevils in Mexico, an area where they are native, and to prevent them from being accidentally introduced into California, Hoddle is working with Jocelyn Millar, a UCR insect pheromone expert. They are leading an effort to find the weevil's pheromone, with the goal of using it to monitor these pests and prevent them from mating in avocado orchards.

Pheromones are chemicals produced and released into the environment by an insect that can be “smelled” by others of its species, and affect their behavior.

“We could flood avocado orchards with so much pheromone that males and females can't find each other, and therefore can't reproduce,” Hoddle said. “This would reduce damage to fruit and enable growers to use less insecticides.”

Alternative control strategies could include mass trapping, using the pheromone as a lure, or an “attract-and-kill” approach, where the pheromone attracts the weevils to small sources of insecticide.

The work to identify, synthesize and test this pheromone in the field is supported by grants from the California Department of Food and Agriculture, as well as the California Avocado Commission.

An initial phase of the project sent Hoddle to a base of operations three hours south of Mexico City, an area with large weevil populations. Using a special permit issued by the USDA, Hoddle brought weevils back to UCR's Insectary and Quarantine facility.

Hoddle and Sean Halloran, a UCR entomology researcher, captured the chemicals that avocado weevils release into the air. Possible pheromone compound formulas were identified from these crude extracts and are now being synthesized in Millar's laboratory.

“Weevil pheromones have complicated structures. When they're made in a lab, they can have left- or right-handed forms,” said Hoddle. Initially, Millar's group made a mixture of both forms to see if the blend would work as an attractant, as it is far cheaper to make the blend than the individual left- or right-handed forms.

Field work in Mexico with the pheromone cocktail by Hoddle, his wife Christina Hoddle, an associate specialist in entomology, and Mexican collaborators did not get a big response from the weevils, suggesting that one of the forms in the blend could be antagonizing the response to the other.

As the next step, the researchers plan to synthesize the individual forms of the chemicals and test the insects' response to each in Mexican avocado orchards.

Because the levels of avocado imports from Mexico are increasing, the risk of an accidental weevil invasion is rising as well. Hoddle is hopeful that the pheromone will be successfully identified and used to lower the risk this pest presents to California's avocado growers.

“We've been fortunate enough to be awarded these grants, so our work can be implemented in Mexico and benefit California at the same time,” Hoddle said. “The tools we develop now can be used to make sure crops from any exporting country are much safer to import into California.”

Consult UC ANR's map to see how close you live to citrus with HLB disease

UC Cooperative Extension developed an online interactive map that allows Californians to see how close they live to citrus trees infected with huanglongbing disease, reported Jeanette Marantos in the Los Angeles Times. This information is critical for the more than 60% of Californians who are growing their own backyard orange, grapefruit, mandarin, lime and other citrus trees.

Huanglongbing is an exotic citrus disease that kills every tree it infects. An exotic insect, the Asian citrus psyllid, spreads the disease from tree to tree. If the disease makes its way into California's commercial citrus production regions, it threatens the state's valuable and iconic citrus industry.

Go to http://ucanr.edu/hlbapp and type in your address. If you are inside the red circle — within two miles of a hot zone — UCCE suggests you remove your citrus trees and plant different types of fruit trees, such as peaches, pears, apples or figs, until researchers find a cure. In the yellow circle — within two to five miles of a hot zone — consider replacing your tree with a non-citrus fruit tree or protect your citrus trees. Find detailed information on home citrus management here https://ucanr.edu/sites/ACP/Homeowner_Options/

“When we first started this program back in 2012, I was encouraging Master Gardeners to teach homeowners how to treat their trees [to discourage psyllids, which are the insects that spread HLB],” she said, “but the complaint came back from the Master Gardeners, ‘I treat my trees but none of my neighbors do, so what's the point?'” said Beth Grafton-Cardwell, UC Cooperative Extension entomology specialist and director of the Lindcove Research and Extension Center in Exeter.

Grafton-Cardwell said the threat is serious. HLB disease devastated Florida's citrus industry when it hit in 2005, destroying half of its acreage and production, and pretty much eliminating residential citrus. 

The battle against the psyllid in California is being helped by the introduction in 2011 of Tamarixia radiata, a parasitic wasp native to Pakistan, by UC Cooperative Extension biological control specialist Mark Hoddle and his entomologist wife Christina Hoddle.

"We've had psyllid here [in California] since 2008, but we still have a lot of oranges,” Hoddle said. “The disease hasn't swept through California the way it did through Florida, and I believe our biological control program is why. Psyllid populations have decreased by 70% to 80% since our first parasite release in 2011. We haven't wiped out HLB in citrus trees, but we have mitigated the risk.”

Three UC ANR programs receive research grants from CDFA

The California Department of Food and Agriculture has awarded more than $1 million to fund three UC Agriculture and Natural Resources integrated pest management projects to research insects that have the potential to become pests in California agriculture. Each of the three-year projects received strong support from commodities which could be affected by invasive pests.

The projects that were awarded the funds are:

Proactive management of avocado seed and stem feeding weevils, led by UC Cooperative Extension specialist Mark Hoddle and entomology professor Jocelyn Millar, both at UC Riverside, will receive $348,893. This project will develop pheromones, identify natural enemies in the host range, and quantify flight capacity of the avocado seed weevils. Native to Mexico and invasive in Ecuador, these weevils feed directly on avocados and could cause substantial damage to the California avocado industry. The California Avocado Commission pledged an additional $150,000 to support this project. The work will be conducted at UC Riverside and in Mexico.

A proactive approach to prepare for the invasion of Tuta absoluta into California, led by UCCE specialist Ian Grettenberger, will receive $499,847. T. absoluta, a tomato leafminer, is a serious pest throughout Europe, Africa, western Asia and South and Central America and could decimate California's tomato industry. This project will proactively test targeted insecticides, identify native natural enemies that could be used in biological control, and conduct work to assist in breeding plants resistant to this pest. This project will be conducted at UC Davis, throughout California, and in Chile and Peru.

Detection, biology and control of the exotic Sweede midge for California cole crops, led by UCCE area IPM advisor Alejandro Del Pozo-Valdivia,  UCCE specialist Ian Grettenberger and USDA research entomologist Daniel Hasegawa. Swede midge is a pest of cole crops in the Northeastern U.S. and Canada and could cause significant management issues for California's large cole crop industry. This project will collect important information about the biology of Swede midge, test low impact insecticides and botanical products as options for control, assess the possibility of weeds as alternative hosts, and work with growers to start monitoring for the pest. This project will be conducted at UC Davis and in the Salinas Valley.

 

Goldspotted oak borer continues to spread

The invasive beetle, goldspotted oak borer (GSOB), has been found in the mountain community of Sugarloaf near Big Bear in San Bernardino County, reported the Chino Champion. The detection causes concern for other nearby communities where oak trees are prized.

All stages of the insect - larval, pupal and adult - were found underneath bark in dying black oak trees on private property. GSOB is a native of Guatemala, southern Mexico and southeastern Arizona. It was first collected in San Diego County in 2004. To limit the pest's spread, officials ask Californians not to transport firewood from one location to another.

"It realistically should be treated like a quarantine situation," said Doug Yanega of the UC Riverside Department of Entomology. "All it takes is a few people who don't know any better or think the rules don't apply to them to infest new areas."

The Chino Hills area has nearly 4,000 oak trees in parks, landscaping and parkways, not including trees on private property and city open space. 

"The goldspotted oak borer posts an unprecedented threat to native oaks in Southern California," said UC Cooperative Extension specialist Mark Hoddle, director of the the Center for Invasive Species Research at UC Riverside. "Hiking trails and campsites have been closed because of the risk of branches dropping from dead trees."

For more information about GSOB, see the UC Cooperative Extension GSOB website.

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