Registered Pesticides and Citrus Terpenes as Blackbird Repellents for Rice

Abstract: Nonlethal management alternatives are needed to minimize bird depredation of agricultural crops. We conducted 8 caged feeding tests and 2 field studies to evaluate 2 registered fungicides (GWN-4770, Gowan Company, Yuma, AZ; Quadris®, Syngenta Crop Protection, Greensboro, NC), a neem oil insecticide (Aza-Direct®, Gowan Company), and a novel terpene formulation (Gander Gone, Natural Earth Products, Winter Springs, FL) as avian repellents. For all candidate repellents, red-winged blackbirds (Agelaius phoeniceus) discriminated between untreated and treated rice during preference-testing in captivity. We observed a positive concentration-response relationship among birds offered rice treated with 2,500 ppm, 5,000 ppm, 7,500 ppm, 11,000 ppm, or 22,000 ppm GWN-4770. Relative to pretreatment, blackbirds consumed 34% and 77% less rice treated with 11,000 ppm and 22,000 ppm GWN-4770, respectively, during the concentration-response test. Maximum repellency among other tested compounds was <40% during the concentration-response test. Blackbirds consumed 28% of rice seeds treated with 20,000 ppm GWN-4770 and 68% of untreated seeds broadcast within rice fields in southwestern Louisiana, USA. We observed 50% fewer unprotected seedlings than those treated with 10,000 ppm GWN-4770 within a drill-seeded rice field in southeastern Missouri, USA. The manufacturer subsequently applied for a United States patent for the active ingredient of GWN-4770 as an avian repellent. Although additional registration criteria and formulation optimization must be satisfied to enable the commercial availability of GWN-4770 as an avian repellent, additional efficacy studies of GWN-4770 and other promising repellents under extended field conditions are warranted for protection of newly planted and ripening rice.