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Funded Project

Funding Program: Regional IPM Grants (S-RIPM)

Project Title: Argentine Ant IPM in the urban landscape with food source reductions and baits

Project Director (PD): Jules Silverman [1]

Lead State: NC Lead Organization: NC State University

Research Funding: $94,432

Start Date: May-16-2008 End Date: May-15-2010

Pests Involved: Argentine ant

Site/Commodity: urban

Summary: The Southeastern US is now infested with the Argentine ant, Linepithema humile. This introduced invasive species is a serious urban and agricultural pest throughout California and may repeat it's negative impact in the southeast with several established populations already in this state. North Carolina still maintains an important agricultural based economy with burgeoning urbanization. Recent NC Dept Agriculture. statistics value the NC green industry at $8.6 billion and USDA ranks NC 7th in agricultural cash receipts. Management of Argentine ant populations is constrained by many factors, including the ants ready access to a relatively abundant and consistent food source; honeydew from aphids, soft scales and mealybugs. Currently, only chemical insecticides are utilized in attempts to control Argentine ants and these are frequently misapplied, overused, and are generally ineffective because the large, diffuse colony structure of Argentine ants makes nests difficult to locate and treat. Delivery of one insecticide form, bait, does not require precise location of the nest and has minimal effects on non-target organisms; however, baits often fail because they are rejected in favor of Sternorrhyncha honeydew. The overall goal of this project is to develop an alternative pest management system for Argentine ants and is related to the USDAs national integrated pest management (IPM) roadmap that calls for increasing the use of IPM systems to reduce potential human health risks and minimize adverse environmental effects from pest and related management strategies in residential and public areas. Specifically, we aim to develop a novel management approach whereby Argentine ants are simultaneously prevented from accessing their preferred food source and provided insecticidal bait. We predict that while Sternorrhyncha reductions alone will negatively impact Argentine ant populations, insecticidal baits will further depress ant numbers, being consumed when honeydew is scarce. We will test our hypothesis in two separate urban settings (1) commercial business park (2) residential neighborhood, where Sternorrhyncha populations on ornamental and shade trees are reduced with a winter dormant oil application or a soilinjected systemic treatment, which is followed by ant baiting. We will also evaluate a low nontarget risk treatment whereby Argentine ants are prevented from reaching Sternorrhyncha in the canopy through the placement of sticky barriers around tree trunks, in conjunction with baiting. In addition to assessing the technical merit of this approach, we will conduct surveys of homeowner/enduser perceptions of performance, and extend the results of this research to stakeholders through workshops and Cooperative Extension Service mailings. Because the Argentine ant is found throughout much of the southeastern U.S. and California, the pest management program developed here, in North Carolina, will apply equally well to other regions of the U.S. Moreover, federal and local regulations have dictated the implementation of IPM programs in and around municipalities (offices, hospitals, schools, recreation areas) and results obtained from research and implementation of this proposal around private residences will be applicable to other peridomestic environments. Objectives: 1) Determine the relationship between Sternorrhyncha and Argentine ant numbers on ornamental trees. 2) Identify the system components to implement in objective 3. 3) Conduct field trials to assess whether Sternorrhyncha population management or restricted access to Sternorrhyncha with or without insecticidal bait reduces Argentine ant populations. 4) Technology transfer of this IPM approach to stakeholders through the development of demonstration plots and special workshops.

Final Report:

Impacts From report submitted by the PI to USDA report system We have provided a new approach to Argentine ant population management. By reducing access to their natural food we can better control this pest with toxic baits. The challenge will be to have more efficacious baits in our Argentine ant management toolbox.

Results From report submitted by the PI to USDA report system PROGRESS: 2008/07 TO 2011/06 OUTPUTS: The most significant technical outputs of this project were finding that Argentine ant nest numbers fell dramatically in the mulch around ant-excluded trees; however there was no reduction in Argentine ant numbers caught in pitfalls around trees with or without canopy access. We added 0.5% boric acid bait stations at the base of the red maples and monitored bait consumption. Pitfall and nest counts were not affected by the addition of boric acid although bait consumption was lower around ant-excluded trees, suggesting that restricting access to honeydew-producing Hemiptera did not enhance bait performance. We attribute this result to the increased distance Argentine ant workers had to trail from nest to bait station when not tending nearby terrapin scale. We followed this finding with additional experiments. We investigated the effect of various hemipteran control strategies on terrapin scale densities and measured their indirect effect on local Argentine ant densities and foraging effort. We then determined if this indirect treatment strategy improved the performance of an ant bait. A horticultural oil spray and soil application of the systemic insecticide, imidacloprid, had no effect on terrapin scale numbers. However, trunk-injected dicrotophos caused a reduction in scale and a decline in local Argentine ant nest density and canopy foraging effort. We also recorded a reduction in local Argentine ant ground foraging when large amounts of liquid bait were applied, yet found no evidence that combining dicrotophos with liquid ant bait performed better than each treatment alone. We suggest that a strategy of combined hemipteran control plus application of liquid ant bait can reduce local Argentine ant densities, when both components of this system are highly efficacious. Regarding education and technology transfer, we developed and distributed a short Powerpoint presentation about Argentine ant biology, identification and management to all horticultural Cooperative Extension agents in NC to utilize for themselves and in their training sessions. We published Extension insect Note #140, "Argentine Ants in the Landscape and Home" was written as a web document and posted on the internet for reference and referral to the public and Extension agents. We posted news bulletin in weekly web newsletter, NC Pest News, Vol 25, No 17. August 2010. "Argentine Ants in the Landscape". We covered Argentine ants in a regional workshop for professional landscapers, Feb. 2011. Attnd 720. We covered Argentine ants in several countywide Master Gardener volunteer training sessions, 2011. We covered Argentine ant identification in regional Pest Control Technician, Ant Identification Workshop, Jan, 2011. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project. IMPACT: 2008/07 TO 2011/06 We have provided a new approach to Argentine ant population management. By reducing access to their natural food we can better control this pest with toxic baits. The challenge will be to have more efficacious baits in our Argentine ant management toolbox.

Outcomes N/A

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