Evaluation of Broadcast Applications of Various Contact Insecticides Against Red Imported Fire Ants, Solenopsis invicta Buren 1,2

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1 Evaluation of Broadcast Applications of Various Contact Insecticides Against Red Imported Fire Ants, Solenopsis invicta Buren 1,2 Kelly Loftin, John Hopkins, John Gavin, 3 and Donna Shanklin 4 University of Arkansas Cooperative Extension Service P.O. Box 391, Little Rock, AR USA J. Agric. Urban Entomol. 20(3): (July 2003) ABSTRACT The efficacy of permethrin, bifenthrin, deltamethrin, and fipronil was compared with various rates and formulations of imidacloprid and cyfluthrin against Solenopsis invicta Buren (Hymenoptera: Formicidae), red imported fire ants (RIFAs). Efficacy was determined by collecting foraging RIFAs from each plot. Estimated percent reduction was 86, 61, and 40 for granular imidacloprid, granular cyfluthrin and the 9.55 L/ha (130.7 oz/acre) liquid cyfluthrin/imidacloprid formulation, at 1 day after treatment (DAT), respectively. By 65 DAT only the granular fipronil treated plots had statistically significant ( 0.05) fewer fire ants than the untreated control. Based on these results, the Arkansas Insecticide Recommendations were revised to include fipronil granules for use by Arkansas homeowners for RIFA control. KEY WORDS Hymenoptera, Formicidae, Solenopsis invicta, insecticide efficacy, imidacloprid, fipronil, cyfluthrin, permethrin, bifenthrin, deltamethrin Solenopsis invicta Buren (Hymenoptera: Formicidae), the red imported fire ant (RIFA), arrived in Mobile, Alabama, from South America between 1933 and 1945 (Callcott & Collins 1996). The first documented infestation in Arkansas occurred in 1958 (Loftin et al. 1999). Since 1958, the pest has spread to more than 30 counties in the southern half of Arkansas. Economic losses, including the cost of controls, are estimated at nearly $42 million for Arkansas and $2.5 billion for the 11 RIFA-infested states in the southern United States (Thompson & Wiley 2002). The 2002 Insecticide Recommendations for Arkansas (Johnson 2002) lists many bait products for homeowner management of RIFAs, but there are no homeowner recommendations for contact insecticides for broadcast application. Recently, several new materials have become available, including imidacloprid, fipronil, deltamethrin, and cyfluthrin. The objective of this study was to evaluate the efficacy of selected broadcast applications of contact insecticides available to homeowners. 1 Accepted for publication 16 April 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 Arkansas Cooperative Extension Service is implied. 3 Bradley County, University of Arkansas Cooperative Extension Service, 100 East First Street, Warren, Arkansas USA 4 University of Arkansas Cooperative Extension Service, SEREC, PO Box 3468, Monticello, AR USA 151

2 152 J. Agric. Urban Entomol. Vol. 20, No. 3 (2003) The efficacy of permethrin, bifenthrin, imidacloprid, fipronil, deltamethrin, and cyfluthrin against the RIFA was evaluated. Methods and Materials This trial consisted of nine treatments and three replications in a randomized complete block (RCB) design. The efficacy of permethrin, bifenthrin, deltamethrin, and fipronil was compared with that of the various rates and formulations of imidacloprid and cyfluthrin. Evaluations were conducted in 2002 by collecting foraging fire ants using hot dog baited traps (Jones et al. 1998). The final evaluation included a determination of the presence of RIFA brood. Study site. The study was conducted in Rye, Arkansas, located in Cleveland County in southeast Arkansas. Density of RIFA mounds at the study site was approximately 593 mounds per ha (240 mounds per acre). Grass had been mowed approximately 3 days prior to the study. Design. Eight insecticide treatments and an untreated control were arranged in a RCB with three replicates. Plots were approximately ha (0.25 acre) in size. The treatments and control were randomly allocated within each block. The three blocks corresponded to distinct areas of the study site. Evaluation. Pre- and post-treatment evaluations were conducted using bait stations to collect foraging ants within each plot following the methods of Jones et al. (1998). Bait stations consisted of a 0.64-cm (1/4-inch) hot dog cube placed on a snap vial lid and marked with a wire survey flag. Ten bait stations were arranged in two transects with five bait stations each, located approximately 4.72 m (15 feet) on each side of the center line of each plot. Bait stations within each transect were approximately m (30 feet) apart. Bait was made available to foraging ants for approximately 30 min. The number of RIFA collected from each station in each plot was determined to evaluate product efficacy. The percentage of mounds containing RIFA brood (eggs, larva, and pupa) was determined during the final evaluation, 65 days after treatment (DAT). Ten mounds in each plot were excavated and observed for the presence of RIFA brood. Insecticide applications. The nine treatments are given in Table 1. Granular insecticides were broadcast using a Herd seeder (Herd Seeder Co., Inc., Logansport, Indiana) mounted on a four-wheel ATV mule (Kawasaki Motorcycle Corp., Irvine, California) equipped with a digital speedometer. After calibration, the specified rates were broadcast by matching to the appropriate ground speed and dispersal rate. Liquid insecticide treatment applications were made with a trailer mounted boom sprayer pulled by the same ATV. Liquid treatments were applied at 93 L/ha (10 gallons/acre). Insecticide applications were made on August 6, Statistical analysis. Data collected from bait stations were analyzed within dates using analysis of variance for a RCB design (Analytical Software 2000). The protected LSD procedure was used to determine significant differences in the mean number of foraging RIFAs collected from the various treatments. The percentage of mounds containing RIFA brood (untransformed data) was analyzed using the same procedures as above. Results and Discussion At one DAT the granular imidacloprid, cyfluthrin/imidacloprid 9.55 L/ha (130 oz/acre) liquid, and granular cyfluthrin treatments had significantly fewer RIFA

3 LOFTIN et al.: Evaluation of Contact Insecticides Against RIFA 153 Table 1. Insecticide rates, formulations, and manufacturers of insecticide treatments evaluated against red imported fire ants in Rye, Arkansas, Rate Insecticide a kg a.i./ha kg prod./ha lb. prod./acre Manufacturer Untreated control 0.25% permethrin GR Real Kill Multi Purpose Insecticide 0.147% bifenthrin GR Scotts MaxGuard Insect Protection with Turf Builder 0.2% imidacloprid GR Bayer Advanced Lawn Season-Long Grub Control % fipronil GR Over n Out! 0.1% deltamethrin GR Martin s Delta Shield 0.72% cyfluthrin % imidaclopride EW 0.72% cyfluthrin % imidacloprid EW 0.02 l a.i./ha 3.18l/ha 43.5 oz/acre Research stock supplied by Bayer Environmental Science 0.07 l a.i./ha 9.55l/ha oz/acre Research stock supplied by Bayer Environmental Science 0.1% cyfluthrin GR Bayer Advanced Lawn Power Force a GR, granular; EW, emulsion, oil in water.

4 154 J. Agric. Urban Entomol. Vol. 20, No. 3 (2003) Table 2. Number of RIFA collected from treated plots after broadcast application of selected insecticides in Rye, Arkansas, Treatment a Rate Mean number RIFA per bait station % Mounds with brood 0 DAT b 1 DAT 2 DAT 3 DAT 7 DAT 14 DAT 35 DAT 65 DAT 65 DAT Untreated control 32.5a 50.8a 36.5a 22.2ab 71.7ab 42.8ab 55.8ab 56.8ab 75ab Permethrin GR 0.24 kg a.i./ha 52.0a 52.5a 38.3a 33.5a 70.0ab 50.0ab 57.5a 70.8a 97a Bifenthrin GR 0.22 kg a.i./ha 34.0a 34.2abc 30.0a 15.8bcd 34.8de 18.7cd 42.0ab 37.8bc 73ab Imidacloprid GR 0.37 kg a.i./ha 49.2a 5.2d 7.5b 4.2d 19.8e 37.7abc 36.7b 58.5ab 67b Fipronil GR 0.01 kg a.i./ha 37.5a 49.2ab 27.8a 9.5cd 43.3cde 13.5d 9.5c 16.0c 33c Deltamethrin GR 0.10 kg a.i./ha 39.5a 39.7abc 31.1a 20.8ab 55.0abc 35.0abc 45.8ab 61.2ab 80ab imidacloprid EW 0.02 l a.i./ha 33.3a 40.4ab 34.2a 23.3ab 70.0ab 54.2a 48.3ab 61.2ab 71ab imidacloprid EW 0.07 l a.i./ha 40.8a 27.8bcd 32.3a 21.7ab 75.8a 52.0a 60.1a 60.0ab 83ab Cyfluthrin GR 0.15 kg a.i./ha 31.0a 17.0cd 21.3ab 21.5ab 50.0abc 31.2bcd 46.0ab 53.8ab 71ab F df P Means within a column followed by the same letter are not significantly different using the protected LSD mean separation procedure ( 0.05). a GR, granular; EW, emulsion, oil in water. b DAT, Days after treatment.

5 LOFTIN et al.: Evaluation of Contact Insecticides Against RIFA 155 Table 3. Estimated percent population reduction of RIFA after broadcast application with selected insecticides in Rye, Arkansas, Treatment a Rate Population reduction post treatment (%) % Reduction in mounds with brood 1 DAT b 2 DAT 3 DAT 7 DAT 14 DAT 35 DAT 65 DAT 65 DAT Permethrin GR 0.24 kg a.i./ha 17c 27b 0c 11bc 7bc 0a 13b 3b Bifenthrin GR 0.22 kg a.i./ha 36bc 27b 30bc 49ab 56a 21a 31ab 16b Imidacloprid GR 0.37 kg a.i./ha 86a 64a 81a 72a 16bc 33a 25b 10b Fipronil GR 0.01 kg a.i./ha 16c 25b 58ab 38abc 68a 83b 70a 52a Deltamethrin GR 0.10 kg a.i./ha 29bc 24b 10c 21bc 23bc 20a 0b 3b imidacloprid EW 0.02 l a.i./ha 27c 20b 4c 9c 5c 19a 1b 17b imidacloprid EW 0.07 l a.i./ha 40bc 21b 11c 2c 2c 13a 5b 6b Cyfluthrin GR 0.15 kg a.i./ha 61ab 39ab 23bc 28bc 29b 18a 15b 8b F df p Means within a column followed by the same letter are not significantly different using the protected LSD mean separation procedure ( 0.05). a GR, granular; EW, emulsion, oil in water. b DAT, days after treatment.

6 156 J. Agric. Urban Entomol. Vol. 20, No. 3 (2003) than the untreated control (Table 2), with percent reduction of 86, 61, and 40 for granular imidacloprid, granular cyfluthrin, and cyfluthrin/imidacloprid 9.55 L/ha (130.7 oz/acre) liquid, respectively (Table 3). The granular imidacloprid treatment maintained this trend through 7 DAT. The bifenthrin and granular fipronil treatments began showing significant reduction in the number of RIFA collected from bait stations at 3 DAT. The granular fipronil treatment had fewer RIFA than did the untreated control throughout the remainder of the study. In contrast, the granular bifenthrin treatments maintained significant levels of control only through 14 DAT. Significant reductions in the number of RIFA collected from bait stations were never achieved with deltamethrin, permethrin, or the cyfluthrin/ imidacloprid 3.18 L/ha (43.5 oz/acre) combination. By 65 DAT only the fipronil plots had a significant reduction in the numbers of RIFA compared with the control. Fipronil was the only insecticide treatment to show a statistically significant reduction in the proportion of RIFA mounds containing brood (Table 2). Fipronil application resulted in a 52% reduction compared with the untreated control (Table 3). With the loss of chlorpyrifos and diazinon as contact insecticides for broadcast application against RIFAs, Arkansas homeowners were left without an alternative contact insecticide. Results from this study show that the fipronil formulation tested can be used as a suitable substitute contact insecticide in managing RIFA. The University of Arkansas, Cooperative Extension Service publication, MP144, 2003 Insecticide Recommendations for Arkansas (Greene 2003) was subsequently revised to include this insecticide for homeowner use in controlling RIFAs. Acknowledgment The authors wish to acknowledge Bayer Environmental Science for support of this project. References Cited Analytical Software Statistix 7 for Windows, Tallahassee, Florida, 333 pp. Callcott, A.-M. A. & H. L. Collins Invasion and range expansion of red imported fire ants (Hymenoptera: Formicidae) in North America from Florida Entomol. 79: Greene, J. K. (ed.) Insecticide recommendations for Arkansas. University of Arkansas Cooperative Extension Service. Little Rock, Arkansas. MP144. p Johnson, D. R. (ed.) Insecticide recommendations for Arkansas. University of Arkansas Cooperative Extension Service. Little Rock, Arkansas. MP144. p Jones, D., L. Thompson & K. Davis Measuring insecticide efficacy: counting fire ant mounds vs. bait station sampling, pp In Proceedings, 1998 Imported fire ant conference, Hot Springs, Arkansas, 192 pp. Loftin, K. M., D. Shanklin & D. Blackburn The federal imported fire ant quarantine. University of Arkansas Cooperative Extension Service. Little Rock, Arkansas. Fact Sheet FSA N, 4 pp. Thompson, L. C. & S. Wiley Annual losses caused by red imported fire ants to households in the southern U.S., pp In Proceeding, 2002 Imported fire ant conference, Athens, Georgia, 173 pp.