Submitted to: Journal of Entomological Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/11/2004
Publication Date: 10/1/2005
Citation: Chen, J. 2005. Assessment of Repellency of Nine Phthalates Against Red Imported Fire Ant (Hymenoptera: Formicidae) Workers Using Ant Digging Behavior. Journal of Entomological Science. 40: 368-377. Interpretive Summary: Repellants can be used to exclude fire ants from sensitive areas, such as school, hospitals, and nursing houses. In addition, repellants can be used to exclude fire ants from nursery stocks in infested areas. In this study, a fast easy-to-perform fire ant repellency bioassay was developed by taking advantage of fire ant digging behavior. By using this bioassay, dimethyl and diethyl phthalates were found to be strong fire ant repellants. This bioassay may facilitate the finding of new fire ant repellants. Dimethyl and diethyl phthalates may be useful in various fire ant repellant formulations.
Technical Abstract: A new method was developed for evaluating chemical repellency to red imported fire ants based on fire ant digging behavior. The active ingredient was incorporated into sand within a liquid scintillation vial with an entry hole on the cap. Fire ants dug and removed sand from the vial through the entry hole. The differences in amount of sand removed from the treated and control vials were used to evaluate chemical repellency. Detail descriptions of the test arena, apparatus, and experimental design were presented. The possible cross-contamination between vials in the two-choice test, caused by fire ants moving sand from one vial to another, was checked by using Congo Red dyed soil for one of the choices. No cross-contamination was found in any of the 20 vials 24 h after fire ants were released in the test arena. Results of multiple-choice tests showed that, of 9 phthalates, dimethyl and diethyl phthalates were most repellent to red imported fire ants. Two-choice tests on a series of concentrations of dimethyl and diethyl phthalates revealed that among concentrations being tested, the minimum repellent concentration within 24 h was 100 ppm for both. The advantages of this new method are discussed.