Fire Ant Trails:
News from the Texas Imported Fire Ant Research & Management Plan
December 2001 Vol. V No. 2

Table of Contents

24©) Registration for Texas: “Hopper Blend” of Hydramethylnon Plus Methoprene

Fipronil: A New Insecticide Class and Products for Imported Fire Ant Control

24(c) Registration for Texas: “Hopper Blend” of Hydramethylnon Plus Methoprene

The Texas Department of Agriculture (November 30, 2001 memorandum from Phil Tham, Deputy Assistant Director for the Pesticide Programs Division) has issued a 24(c) (Special Local Needs) registration for the “hopper blend” application of Amdro® or Siege® Pro plus Extinguish™ Professional Ant Bait (SLN TX - 010016, enclosed).          The application of the blend of 0.75 lb. Amdro® or Siege® Pro Fire Ant Bait (50% hydramethylnon ) blended with 0.75 lb. Extinguish™ Professional Fire Ant Bait (50% methoprene or other “juvenoid” Insect Growth Regulator fire ant bait product) and applied 1.5 pounds of the blended products per acre has repeatedly resulted in a relatively quick and long-lasting suppression of red imported fire ant mound numbers in replicated tests (see http://fireant.tamu.edu under research and applied research). Neither product applied alone produces this effect (see illustration).

     Hydramethylnon (Amdro® or Siege® Pro) produces a quick reduction within 2 to 6 weeks of treatment, but re-infestation may begin thereafter resulting in the need for perhaps two to four treatments per year to maintain control.

     Methoprene (Extinguish™) bait produces a slow reduction characteristic of an Insect Growth Regulator (IGR) bait product, requiring 2 to 6 months to achieve maximum suppression. However, the suppression achieved with the use of methoprene bait can last for a full year.

     The “hopper blend” treatment provides the best of both products. Both products are cleared for use in pastures and rangelands. This treatment, can provide an economic savings to agricultural producers by providing a more effective control profile than can be provided by applying either product alone at the same cost, and by increasing the time interval needed between treatments to maintain control.

     The red imported fire ant, Solenopsis invicta Buren, has been documented to cost Texas cattle production systems about $67 million per year in losses to hay production, equipment damage, livestock injury and death (Barr and Drees 1996). Current treatments are perceived to be too expensive to use in a sustainable manner by many producers. By providing producers the option of using a hopper blend treatment to obtain a quick and longer period of control for the same price, the acceptability of control should improve.

Fipronil: A New Insecticide Class and Products for Imported Fire Ant Control

     Fipronil, a contact insecticide, belongs to the phenyl pyrazole class of insecticides. As nervous system toxicants, they block the passage of chlorine ions by interacting with gamma-aminobuteric acid (GABA)-gated chloride channels on nerve cell membranes.

     Other fipronil-containing products currently available include the termiticide, Termidor®, Combat® and Maxforce® indoor ant and cockroach bait stations and Frontline®, a flea control product for use on pets. The Environmental Protection Agency registered fipronil for use against the red imported fire ant control in December 2000 in a bait formulation and in contact granular formulations (Williams et al. 2001).

     Aventis Environmental Science introduced three fipronil products in October 2001.

      Chipco® FireStar™ Fire Ant Bait (CAUTION) is formulated at 0.00015% broadcadst-applied at 1.5 TO 15.0 lbs product per acre or used to treat individual ant nests using 5 Tbsp of product per mound. It is registered for use on home lawns, golf courses and commercial and recreational turf, adjacent landscape beds and sod farms.

     Field trial results. The bait formulation (15 ug/mg a.i.) at either 1.7 or 3.4 kg formulated bait per hectare, provided over 80% colony mortality 6 to 12 weeks after treatment (Collins and Callcott 1998). Note: The formulation used in this field tested may not be the same as that on which this product will be released.

      Chipco® TopChoice™ Insecticide (CAUTION) is a granular formulation formulated as a 0.0143% material and is to be applied at 87 lbs of product per acre to achieve a 0.0125 lb a.i. per acre rate. This product is registered for use on turf grass including golf turf, sports fields, commercial lawns, cemeteries, parks, campsites, recreational areas, home lawns, school grounds, sod farms, and landscape beds.

     The approximate length of control is 1 year! Two applications may only be used on sod farms within the USDA APHIS Quarantine areas. The label also lists mole crickets, nuisance ants (Lasius neoniger), fleas and ticks as pests that will be controlled for a limited time where this fire ant control product is used.

     Field trials. The 0.0143% formulation has been tested several times in the past few years in Texas (C. L. Barr, pers. comm.). A test initiated in the spring of 1999 in Bryan, Texas showed over 95% control from 12 through 52 weeks post-application at the 0.0125 lb/acre rate. Initial control appeared within 2 to 4 weeks with a maximum control reached within 8 weeks during warm weather. Initial control may likely take longer when applied after cold or dry weather has set in.

      Chipco® Choice™ Insecticide (CAUTION), formerly only registered for mole cricket control with a slit application, now includes fire ants on the product label. It is a 0.1% granule applied at 12.5 lb product per acre to achieve a 0.0125 lb a.i./acre rate. Use sites and other arthropods controlled are similar to that found on the Chico TopChoice label.

     Field trial results. One granular formulation (0.1% fipronil applied at 0.01875 and 0.250 lb a.i. per acre) provided 96% control throughout a 30-week trial period (Sparks and Diffie 1998). A test in Texas in 1997 of the 0.1% formulation at the labeled rate resulted in over 90% control at 14 months post-treatment with 70% control maintained at 27 months after application (C. L. Barr, pers. comm.)! The manufacturer claims that 4 to 6 weeks following application, Chipco TopChoice will typically achieve up to 95 percent control of fire ants and prevent new infestations for up to 52 weeks with a single application .

     In early spring 2002, GardenTech® is expected to be introducing Over 'n Out! Fire Ant Killer, another fipronil granular formulation to retail markets.

     Precautions. Because of concerns abou toxicity of fipronil to some aquatic organisms, granular products are not to be applied within 15 ft of fresh or 60 ft of estuarine bodies of water.

     Cost. According to Ann Wiese, representative for Aventis, the estimated cost for Chipco FireStar will be $10 to $11 per pound and Chipco TopChoice will be $220 per acre. The estimated cost for Over 'n Out, according to Darren Horst, vice president for GardenTech, should be about $19.97 per 10 lbs, which will treat 5,000 square feet of yard.

     Although granular fipronil products are contact insecticides, they have an initial performance that appears more like that of a fast-acting bait, such as Amdro^®, where maximum control takes a few weeks. Most contact insecticides show maximum control in a few days. Conversely, fipronil has extremely long true residual activity that prevents reinvasion of an area longer than baits or other contact insecticides. Knowledge of the initial delay and extended length of control are key educational points to help consumers and customers accept the products.

     One major advantage fipronil granular products have is that they appear to be effective regardless of temperature and ant food preference, unlike baits where active ant foraging is essential to their performance. One test in Texas was applied in early November 2000 and resulted in over 80% control at 8 weeks with over 90% control at 5 months. Pilot applications of bait at the time indicated no ant foraging or bait acceptance due to cool weather.

     Fipronil fire ant control products will add to the arsenal available for the integrated pest management of the imported fire ant. Granular formulations will serve to replace diazinon and chlorpyrifos (Dursban®) products removed from retail markets, and compete directly with pyrethroid insecticide products like Talstar® (bifenthrin) for professional treatments of landscapes, commercial sod and nursery crops. Few other products provide the level of control for this duration of time with a single broadcast treatment of the granules.

Citations:

       Collins, H. L. and A.-M. A. Callcott. 1998. Fipronil: an ultra-low-dose bait toxicant for control of red imported fire ants (Hymenoptera: Formicidae). Fla. Entomol. 81:407-415.

       Sparks, B. and S. Diffie. 1998. Evaluation of broadcast treatments of fipronil for control of red imported fire ants in Georgia, pp. 159-162. In D. Shanklin (ed), Proceedings Imported Fire Ant Research Conference, Hot Springs, AR.

<     Williams, D. F., H. L. Collins and D. Oi. 2001. The red imported fire ant (Hymenoptera: Formicidae): An historical perspective of treatment programs and the development of chemical baits for control. American Entomologist 47(3):146-159.

Prepared by: Bastiaan “Bart” M. Drees,
Director, Texas Imported Fire Ant Project



      Department of Entomology

      412 Minnie Belle Heep Bldg.

      Texas A&M University

      College Station, Texas 77843-2475

      409/845-5878; FAX: 409/845-7029

b-drees@tamu.edu; http://fireant.tamu.edu

The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Texas Cooperative Extension or the Texas Agricultural Experiment Station is implied.