- Author: 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.
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.
- Author: Dong-Hwan Choe
Benning Le, a MS student from the Choe laboratory successfully defended his MS thesis today (March 9, 2022). Benning's thesis research was on the development and laboratory / field testing of boric acid hydrogel bait targeting Argentine ant populations in agricultural settings. Benning is one of the students who went through our department's new graduate program, the combined BS+MS (4+1) program.
Congrats, Benning!
For more information regarding the UCR Entomology's combined BS+MS program, please click here.
/span>- Author: Dong Hwan Choe
Our research on Argentine ant IPM was published in August 2021 issue of Journal of Economic Entomology (JEE).
Choe, D.-H., J.-W. Tay, K. Campbell, H. Park, L. Greenberg, and M. K. Rust. 2021. Development and demonstration of low-impact IPM strategy to control Argentine ants (Hymenoptera: Formicidae) in urban residential settings. J. Econ. Entomol. 114: 1752–1757.
In addition, the photo showing a pair of Argentine ant workers feeding on a biodegradable hydrogel bait (made form alginate compound) was selected as the cover page for August 2021 issue of JEE. The biodegradable hydrogel bait with boric acid as the active ingredient was incorporated as the maintenance treatment option for the study.
To find more about the research, please visit here to access the full research article.
/span>
- Author: Dong-Hwan Choe
- Author: Kathleen Campbell
- Author: Michael K Rust
Many parks, recreational areas, and outdoor venues in California are home to yellowjacket wasps (Vespula spp.). Yellowjackets are commonly attracted to human food items, creating a serious nuisance and a potential stinging threat. If found, nests (usually underground) can be effectively treated with targeted insecticide applications (e.g., dusts containing pyrethroids). However, baiting could be a feasible alternative method to suppress yellowjackets over a wide area, especially if nests cannot be located. Currently, only one active ingredient (esfenvalerate) is registered for use within bait in California to control yellowjackets, and its efficacy is marginal because it is repellent and fast-acting. Effective active ingredients and optimal bait formulations have yet to be identified.
Foraging wasps seek out protein-rich foods for developing larvae in the nest. These foragers have strong preferences for some meats, and in the past, meats impregnated with insecticides have been used as baits. However, meat loses its attractiveness after less than a day, requiring the use of fresh meat, which has been a major hurdle in developing a commercial ”ready-to-use” bait product.
To overcome this challenge, a team of researchers from the University of California conducted experimental trials using non-meat materials as matrices for yellowjacket baits. Due to their high absorbency of water and water-soluble compounds as well as biological inertness, hydrogels were considered as possible candidates for this use. As a first step in this investigation, we observed whether foraging western yellowjacket wasps (V. pensylvanica) would accept polyacrylamide hydrogel crystals that were hydrated with chicken juice containing a toxicant.
Field Trials
The study was conducted at two different sites in Southern California. Site A was a private country club (~15 acres) with supporting recreational infrastructure (e.g., picnic tables, barbecue facilities, children's playgrounds, etc.). The site was surrounded by mixed conifer and oak forest. Site B was a multiple-use regional park (~161 acres) surrounded by undeveloped wilderness areas composed primarily of riparian and coastal sage scrub. Yellowjacket foraging activity was monitored using traps containing a chemical lure, heptyl butyrate.
In 2014 and 2016, sites were baited with hydrogel bait with 0.025% (wt/wt) fipronil*. Ten yellowjackets per trap per day was used as an action threshold for baiting. To prevent consumption by non-target organisms, the bait was provided at “bait stations” within three small plastic cups placed inside a cage.
Wasps were readily attracted to the bait, manipulated the bait with their mandibles, and flew away with small pieces of the bait (Figure 1). After 24 hours, the approximate amount of bait removed from in each cup in grams (g) was estimated.
Results
For Site A, the estimated amount of bait removed per cup was 8.3–16.5 g or about 27–83% of the bait provided. For Site B, estimated amount of bait removed per cup was 5.8–8.0 g or 29–40% of the bait provided. Monitoring data clearly indicated that yellowjacket foraging activity in baited areas dramatically decreased (~74– 96% reduction) immediately after baiting (Figure 2).
The behavioral observations at the bait stations and the amount of bait taken clearly indicated that polyacrylamide hydrogel was an excellent matrix for yellowjacket baiting. The meat-like physical texture and chemical inertness of the hydrogel may explain its acceptance by foraging yellowjackets. With its ability to absorb large amounts of liquids and to resist evaporation, hydrogel bait might also remain palatable for longer periods of time compared with meat-based bait.
The use of hydrogel for bait formulation may enable manufacturers to develop a commercial ready-to-use bait product for yellowjacket control. Hydrogel baits could be pre-packaged in bait containers, though dehydrated formulations would need to be hydrated with a prescribed amount of water before use. We observed that very few non-target insects were attracted to these baits; Argentine ants and velvety tree ants were occasionally seen foraging at the bait stations. Ants were excluded by using commonly available pyrethroid-impregnated “ant guards” designed for hummingbird feeders. This study used the liquid contents from canned chicken meat as an attractant/feeding stimulant. We are currently working on replacing this “chicken juice” with a mixture of synthetic and natural attractants and feeding stimulants which would be better suited for commercialization.
*Use of fipronil in combination with chicken meat (or juice) is strictly experimental and is not registered for yellowjacket control in California. Such use by licensed professionals would currently be considered illegal.
[Originally published in the Winter 2020 issue of the Green Bulletin.]
- Author: Dong-Hwan Choe
Our postdoctoral scholar, Dr. Jia-Wei Tay, has successfully completed her postoctoral research, and will be leaving the Choe laboratory. Dr. Tay has been working on a novel baiting system (i.e., biodegradable hydrogel bait) for Argentine ant, one of the most important invasive pest ant species in California. She will be taking a new position in University of Hawaii soon, working on urban / structural insects. For more about her research, visit http://www.jiaweitay.com/.
The lab members had the farewell lunch with Dr. Tay on Dec 4, 2018.
Good luck and all the best for your new endeavor, Dr. Tay!