- Author: Ben Faber
Argentine Ant is the great protector of many pests found on plants. Without the Argentine, many pests would not be so much of a problem. In many crops, like cherimoya and passionfruit, mealy bug can become so severe that fruit will stop growing and fall off the tree. Controlling Argentine, makes it possible for predators and parasites to do their thing in bringing them under control. Watch these two videos to see how hoverflies (syrphids) can help biocontrol and how Argentine Ant control can help that biocontrol
Citrus Psyllids Bribe Ants With Strings Of Candy Poop | Deep Look - YouTube
How Hoverflies Spawn Maggots that Sweeten Your Oranges | Deep Look - YouTube
Cherimoya fruit and stems covered with mealy bug.
- Author: Ben Faber
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Synergizing IPM of Argentine ant and biocontrol of sap sucking pests with biodegradable hydrogels, infra-red sensors, and cover crops in commercial citrus orchards
Ivan Milosavljevi?, Department of Entomology, University of California, Riverside, CA
Nicola A. Irvin, Department of Entomology, University of California, Riverside, CA
Kelsey A. McCalla, Department of Environmental Science, Policy, and Management University of California, Berkeley, CA
Mark S. Hoddle, Department of Entomology, University of California, Riverside, CA
Argentine Ant control critical for IPM in citrus groves
The invasive Argentine ant (AA) (Linepithema humile) is a serious impediment to the biological control of sap sucking pests (SSPs) in citrus orchards (Hoddle et al. 2022). SSPs include mealybugs, scales, aphids, and Asian citrus psyllid (ACP), the vector of a bacterium that causes HLB, a lethal citrus. AA protect >85% of SSPs and >55% of ACP colonies from their natural enemies which exacerbates pest infestations. In return for protection from natural enemies, ants are rewarded for this service by SSP's through the provision of a sugary waste product, honeydew, which ants harvest and return to nests to feed brood and queens. Contact sprays for AA and SSP control applied to soil, trunks, and foliage kill natural enemies, cause secondary pest outbreaks, and increase the likelihood of insecticide resistance developing. IPM of AA and SSPs requires an accurate method of assessing pest densities so that appropriate treatment decisions can be made, precision delivery of insecticides to kill foraging AA is necessary if natural enemies are to be preserved, and enhancement of natural enemies through conservation biocontrol can increase the efficacy of free pest control services provided by natural enemies in citrus orchards.
Enhancing and automating Argentine ant monitoring using infra-red sensors and the internet of things
Efficient and accurate pest monitoring is a key component of IPM programs. There are currently no standardized monitoring programs for assessing AA infestation levels. Visual ant counts are time consuming, tedious, and become inaccurate when counting fatigue sets in. To remedy this problem, we developed and field-tested infrared sensors (IRS) that clamp to irrigation lines to automate ant counts . AA use irrigation lines as super-highways to rapidly move across the orchard floor to reach pest infested citrus trees. Statistical analyses indicated that it is possible to predict with about 85% accuracy the average number of ants ascending tree trunks based on the average number of ants running on irrigation lines. Thus, ant counts made by IRS on lines can be used to accurately predict the average number of ants ascending tree trunks in citrus orchards. Ant counts made by IRS are relayed wirelessly to the cloud where average AA densities are reviewed on an App that is loaded onto a smart device. IRS's eliminate the need for humans to monitor ant densities, they provide block specific estimates of AA activity, and they can potentially operate 24/7/365! We are currently determining the minimum number of IRS needed per acre to estimate ant densities with fixed levels of precision (e.g., 85, 90, 95% accuracy).
Based on accurate ant density estimates treatment decisions can be made, and importantly, just the areas of the orchard exceeding acceptable ant densities can be identified and treated (Schall et al. 2018). Focused applications reduces insecticide use, saves money, and minimizes adverse effects of insecticide use on beneficial non-target species, like natural enemies (McCalla et al. 2020). As part of an AA IPM programs, treatment decisions require action thresholds and when AA densities exceed the action threshold, treatments can be initiated. At this time, there are currently no established action thresholds for AA in citrus. This is an important problem we are currently working on.
(A) Infra-red sensor (IRS) clamped onto an irrigation line in a commercial citrus orchard. (B) Argentine ants use polyethylene irrigation lines that sit on the soils surface as “super-highways” to move from underground nests to tree canopies where they collect honeydew. (C) Close-up of IRS counting Argentine ants running on irrigation lines. (Photos by Mike Lewis and Mark Hoddle, UC Riverside).
Hydrogel baits provided targeted and highly effective Argentine ant control in citrus orchards
Chlorpyrifos, the industry standard insecticide for AA control, was recently banned in California because it poses significant risks to human health. In response to this ban, we developed biodegradable hydrogel beads (HGBs) as an alternative highly specific treatment that targets AA. HGBs contain a 25% sucrose solution, and an ultra-low dose of insecticide (0.0001%). HGB's are applied to the ground under citrus trees and spread out so foraging AA can rapidly find them. Ants imbibe sugar water laced with insecticide, return it to the nest to feed brood and queens which kills them. Consequently, HGB's may provide a superior alternative to plastic liquid bait stations for delivering toxins to AA as bait stations are cost-prohibitive for mass use in orchards. Our lab has demonstrated that both thiamethoxam and an organically approved spinosad formulation are highly efficacious when delivered to AA using HGBs infused with sugar water that is laced with insecticide. Within 2-3 days of HGB applications, AA colonies collapse, and AA densities are reduced by >95% in comparison to untreated plots. Rapid (< 5 days) long term (> 3 months) control of AA results from repeated HGB applications (~3-4 applications ~3 weeks apart over summer). Once AA are controlled long-term reductions in densities of SSPs in citrus results because natural enemies are able to more effectively control SSP's in the absence of AA. We are currently determining the minimum amounts of HGBs, and frequency of applications needed to optimize AA control at the lowest costs to growers.
Using flowering plants to enhance natural enemies of ACP and SSPs in citrus orchards
Our previous work has shown that natural enemies, especially hover flies (syrphids), respond strongly to flowering alyssum (Lobularia maritima) and buckwheat (Fagopyrum esculentum). Field work has also shown that ACP in citrus plots with flowering plants suffer significantly greater levels of natural enemy attack, especially by predatory hover fly larvae, when compared to plots lacking flowering plants. Hover fly larvae are dominant predators attacking ACP nymphs and other SSPs in citrus (Kistner et al. 2016, 2017). Tamarixia radiata, a tiny parasitic wasp has been imported into California from the Punjab of Pakistan to attack ACP nymphs also feed from buckwheat flowers. We have also found that hoverflies in southern California are most active in spring and fall and this is when flowering plants are most beneficial to them. This finding is important as ACP (and SSP) populations are greatest in spring and over fall also. Sowing flowering plants late-February and re-sowing in early-September would synchronize hoverfly activity with ACP population increases. We are currently assessing the efficacy of flowering plants in multiple commercial citrus orchards to the magnitude of reductions in populations of ACP and SSP densities when cover crops are present and absent.
Take home messages
IPM of AA and SSP's in citrus, include ACP, requires new and innovative approaches if long-term sustainable management is to be achieved. To achieve this, we are working on developing a package that combines three tools, HGBs, IRS, and flowering plants that enhance monitoring of AA (IRS), provides targeted highly specific control of AA (HGBs) that in turn relieves natural enemies from pressure of foraging ants which permits them to increase the free pest management service that they provide in citrus orchards. These agroecosystem services provided by natural enemies can be further enhanced through resource provision, cover crops, which provide pollen and nectar to natural enemies. This combination of tools, IRS, HGBs and cover crops, synergizes IPM of AA and biocontrol of sap sucking pests infesting California-grown citrus.
- Author: Ben Faber
CLas-positive Asian citrus psyllid found in commercial grove in Pauma Valley, San Diego County
An Asian citrus psyllid (ACP) sample confirmed positive for Candidatus Liberibacter asiaticus (CLas) – the bacteria that causes Huanglongbing (HLB) – was collected from a commercial citrus grove in the Pauma Valley area of San Diego County. This confirmation marks the first CLas-positive ACP found in a commercial grove in San Diego County and only the second grove detection in California.
The ACP sample was collected during a routine commodity survey conducted by Citrus Pest and Disease Prevention Division (CPDPD) staff. Five adult psyllid samples were pooled and tested for CLas, resulting in confirmation of the bacteria by Citrus Research Board's Jerry Dimitman Laboratory, and later verified by the U.S. Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS).
An expansion of the HLB quarantine zone in San Diego County will not be established as a result of the CLas-positive ACP detection and CPDPD staff are swiftly conducting intensive surveys and collecting samples per the ACP/HLB Action Plan from the perimeter of all commercial groves and residential HLB host plants that are located within a 250-meter radius around the find.
While treatment is not mandatory as a result of the detection, all growers within 250 meters of the find site will be notified by their local Grower Liaison and encouraged to apply insecticides to all HLB host material within the designated area with materials recommended by the University of California (UC).
It is more crucial than ever that we prevent HLB from potentially impacting commercial citrus groves by working to eradicate ACP populations now. The cost to manage the ACP is far less than any potential costs or loss to the industry should HLB take hold in our commercial groves and throughout our state.
Currently, the best way to prevent HLB from infecting California's citrus groves is to stop the spread of the ACP. To do so, we must restrict its movement and suppress existing psyllid populations. It is critical to follow best practices and review recommendations from the UC on how to protect commercial citrus groves from HLB. Regulations are in place to help prevent the spread of the deadly pest and disease. All growers, packers, haulers and nurseries must comply with all California Department of Food and Agriculture (CDFA), county and federal regulations, including quarantines.
Growers in San Diego County may contact their local Grower Liaison Sandra Zwaal, the County Agricultural Commissioner's office or the CDFA Pest Hotline at 800-491-1899 for additional information. If you see or suspect ACP or HLB symptoms in your grove, please notify the CDFA .
HLB Quarantine Update
As of July 8, a total of 3,546 trees and 443 ACP have tested positive via PCR for the bacterium that causes HLB. Trees that test positive are treated for ACP and removed, and the HLB quarantine is expanded. Additional ACP treatments and HLB detection surveys are conducted on a recurring basis to remaining citrus within 250 meters of each detection. Counties where HLB has been detected via PCR testing are Los Angeles, Orange, San Diego, Riverside, San Bernardino and San Diego. To see a map of the current HLB quarantine areas, and other details of locations and numbers of HLB detections, please visit maps.cdfa.ca.gov/WeeklyACPMaps/HLBWeb/HLB_Treatments.pdf.
For information on regulatory and treatment requirements growers can expect when HLB is detected in or near your citrus grove or packing house, please refer to CDFA's Information for Citrus Growers/Grove Managers, Action Plan for ACP and HLB or this summary flier.
Additional ACP/HLB Resources
- New and improved CDFA Citrus Division website: https://www.cdfa.ca.gov/Citrus/
- General ACP/HLB
o Information on the state ACP/HLB program including maps, quarantine information, and a signup option for email alerts: citrusinsider.org/
o Biology of ACP and HLB, detection maps and recommendations for monitoring, eradication and management: ucanr.edu/sites/acp/
o UC IPM recommendations for ACP
o Web-based map to find out how close you are to HLB: ucanr.edu/hlbgrowerapp
o Video on Best Practices in the Field, available in English and Spanish
- Research
o UC Ag Experts Talk presentations on management of various citrus pests and diseases are available for viewing here and here on YouTube.
o Summaries of the latest research to combat HLB: ucanr.edu/sites/scienceforcitrushealth/
o Science-based analyses to guide policy decisions, logistics, and operations: www.datoc.us
- Regulatory/Quarantine
o Sign up for program updates from the Citrus Pest and Disease Prevention Division at www.cdfa/signup-email-updates.
o Regulatory requirements for moving bulk citrus: Information for Citrus Growers
o Summary of regulatory requirements in the event of an HLB detection in commercial citrus: citrusinsider.org/Regulatory-Flyer
- Author: Ben Faber
From:
Cressida Silvers
CA Citrus Pest and Disease Prevention Program
ACP/HLB Grower Liaison
Ventura, Santa Barbara and San Luis Obispo Counties
805 284-3310 (phone or text)
ACP/HLB Resources
- New and improved CDFA Citrus Division website: https://www.cdfa.ca.gov/Citrus/
- General ACP/HLB
o Information on the state ACP/HLB program including maps, quarantine information, and a signup option for email alerts: citrusinsider.org/
o Biology of ACP and HLB, detection maps and recommendations for monitoring, eradication and management: ucanr.edu/sites/acp/
o UC IPM recommendations for ACP
o Web-based map to find out how close you are to HLB: ucanr.edu/hlbgrowerapp
o Video on Best Practices in the Field, available in English and Spanish
- Research
o UC Ag Experts Talk presentations on management of various citrus pests and diseases are available for viewing here and here on YouTube.
o Summaries of the latest research to combat HLB: ucanr.edu/sites/scienceforcitrushealth/
o Science-based analyses to guide policy decisions, logistics, and operations: www.datoc.us
- Regulatory/Quarantine
o Sign up for program updates from the Citrus Pest and Disease Prevention Division at www.cdfa/signup-email-updates.
o Regulatory requirements for moving bulk citrus: Information for Citrus Growers
o Summary of regulatory requirements in the event of an HLB detection in commercial citrus: citrusinsider.org/Regulatory-Flyer