- Author: Ben Faber
Argentine Ant is a very aggressive invader that disrupts native ant populations and at the same time disrupts biocontrol agents that help control, such pests as scale, aphids and mealy bugs in citrus and other tree crop species. They defend these sugar producing sources of energy from attack by predators and parasites, like parasitic wasps and predatory assassin bugs and lady bugs. They increase the threat of Asian Citrus Psyllid and HLB by protecting the psyllid from attack by parasitic Tamarixia.
A careful, well placed chlorpyrifos spray has been used to control Argentine ants. A trunk spray and/or spray on irrigation lines has disrupted their activity with minimal impact on beneficials. This protectant spray keeps the Argentine ants out of the canopies and allows the beneficials access to the pests. Controlling this one species, can have significant impact on biocontrol and the whole need for controlling pests.
Chlorpyrifos is a pesticide that might lose registration and other materials and techniques have been examined over the years as a replacement. A recent procedure has been proposed and used successfully on Santa Cruz Island to control introduced Argentine ants. The ant has caused tremendous disruption in biocontrol and it appears to have been controlled by this new technique. We are in the process of evaluating it's use in citrus. The application technique, costs and materials would need to be modified for use in citrus orchards. The current procedure would not be considered an organic practice since the pesticide material is not registered organic. It might be possible to use an organically registered material in the future.
Protocols for Argentine ant eradication in conservation areas
L.Boser1,C.Hanna2,D.A.Holway3,K.R.Faulkner4,I.Naughton3,K.Merrill5,J.M.Randall1,C.Cory1,D.-H. Choe6 & S. A.Morrison
Journal of Applied Entomology
The Argentine ant (Linepithema humile) is a widespread, abundant and ecologically disruptive invader that is present throughout major portions of coastal California and on half of the California Channel Islands. On Santa Cruz Island, the Argentine ant had invaded about 2% of the island's area in four distinct locations as of 2012. Given the negative ecological effects resulting from Argentine ant invasions,we sought to develop a cost-effective method of eradication. Here, we describe the results of large-scale, field-tested methods for Argentine ant eradication and post-treatment detection. Our eradication protocol employs a novel toxicant-delivery system: an aqueous solution of sucrose and 6 ppm of thiamethoxam mixed with hydrating polyacrylamide beads. Ants feed on the solution present on the bead's surface for about 24h after which time bead dehydration prevents feeding. We distributed hydrated beads by helicopter over 74 ha of infested areas plus a 50-m buffer on 14 occasions between June 2013 and September 2014. Treatments reduced Argentine ant activity to subdetectable levels within four months. In 2014, we conducted a high-intensity detection protocol using lures (n = 55 363) in areas treated in 2013.This effort did not detect Argentine ants. In 2015, we conducted a medium-intensity detection protocol using lures (n=2250) in areas treated in 2013 and 2014 but not searched in 2014; this sampling effort did not detect Argentine ant activity except for a single remnant infestation (c.0.3ha in area),which was retreated in2015.Thec ost of treatments was approximately $1400 per ha; this cost is comparable to other ant eradication efforts. The cost of our preferred detection method, which used lures spaced every 10m,was $500 per ha.These results demonstrate sufficient protocol efficacy to justify expansion of treatments to other infested areas in ecologically sensitive areas.
Photo: Argentine ant and scale