Registered Pesticides and Citrus Terpenes as Blackbird Repellents for Rice

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.