Laboratory Efficacy of Chemical Repellents for Reducing Blackbird Damage in Rice and Sunflower Crops

Abstract: Nonlethal alternatives are needed to manage blackbird (Icterids) damage to rice and sunflower production in the United States. We evaluated 4 registered fungicides on rice seeds (i.e., Allegiance® FL, Thiram 42-S, Trilex®, and Vitavax® 200 preplant seed treatments) and 2 foliar pesticides on sunflower seeds (Cobalt™ insecticide and Flock Buster bird repellent) as candidate blackbird repellents. Red-winged blackbirds (Agelaius phoeniceus) preferred untreated rice relative to rice treated with Thiram (P < 0.001) and Vitavax (P < 0.001), and untreated sunflower relative to sunflower treated with Cobalt (P < 0.001). Blackbirds preferred untreated sunflower relative to sunflower treated with Flock Buster repellent on day 1 of a 4-day preference test (P < 0.001). We observed no difference in consumption of treated versus untreated rice during the Allegiance preference test (P = 0.928), and blackbirds preferred rice treated with Trilex relative to untreated rice (P = 0.003). Although repellency was positively related to tested concentrations of Thiram (P = 0.010), Trilex (P = 0.026), and Vitavax (P < 0.001), maximum repellency was < 50% during our concentration-response tests of these seed treatments. Repellency was also positively related to tested concentrations of Cobalt (P < 0.001), and we observed >80% repellency of sunflower treated with Cobalt at ≥50% of the label rate. We observed no concentration-response relationship for the Allegiance seed treatment (P = 0.341) and Flock Buster repellent (P = 0.952). We recommend implementation of supplemental field studies to compare laboratory efficacy, repellency, and chemical residues of effective avian repellents throughout periods of needed crop protection.     

Blackbird Repellency of Selected Registered Pesticides

Abstract: Bird depredation of agricultural crops is a worldwide problem. New strategies to include chemical repellents are needed to mitigate crop losses. We evaluated 3 preplant seed treatments (Apron XL® LS [Syngenta Crop Protection, Greensboro, NC], Dividend Extreme® [Syngenta], and Maxim® 4 FS [Syngenta]), one foliar insecticide (Karate® with Zeon Technology™ [Syngenta]), and one foliar fungicide (Tilt® [Syngenta]) as potential blackbird repellents in caged feeding trials and a field study. For all repellents tested, 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 25%, 50%, 75%, 100%, or 200% of the manufacturer label for Dividend Extreme, Karate, and Tilt. Relative to pretreatment, blackbirds ate 32% and 69% less rice treated with 100% and 200% Tilt label rates, respectively, during the concentration-response test. Maximum repellency of Dividend Extreme and Karate was 55% at 200% of their label rates. We observed no repellency of a combination of Apron and Maxim at 25–200% label rates during the concentration-response test. We subsequently measured rice crop consumption and propiconazole (active ingredient, Tilt) residues among 10 plots (i.e., netted enclosures) populated with red-winged blackbirds within a maturing rice field. Average mass of rice harvested between treated (Tilt) and untreated subplots did not differ. We recovered an average of 12.3 μg/g propiconazole immediately following the first application and 20.2 μ g/g propiconazole immediately following the second application of Tilt. We recovered <0.1 μ g/g propiconazole on 15 August 2006, just before populating plots with blackbirds. Thus, the label application of Tilt fungicide did not reduce blackbird consumption within a maturing rice field, and residues of the active ingredient were insufficient for repellent efficacy. Additional studies are needed to determine whether higher concentrations of Tilt repel blackbirds under field conditions and to evaluate other potential repellents for protection of newly planted and ripening crops.     

Caffeine Formulation for Avian Repellency

Abstract: Nonlethal management alternatives are needed to reduce avian depredation of agricultural crops. Caffeine has promise as an effective, economical, and environmentally safe avian repellent, yet formulation improvements are needed for field applications. We included sodium benzoate in subsequent formulations to enhance the solubility of caffeine. Red-winged blackbirds (Agelaius phoeniceus) discriminated between untreated rice and rice treated with 250 ppm or 10,000 ppm caffeine and sodium benzoate in captivity. We observed a positive concentration-response relationship among birds offered rice treated with 250 ppm, 1,000 ppm, 2,500 ppm, 5,000 ppm, 10,000 ppm, or 20,000 ppm caffeine and sodium benzoate. Relative to the pretreatment of the concentration-response test, repellency was >85% for rice treated with our 2,500- to 20,000-ppm treatments. We conducted seed germination experiments and associated residue analyses to evaluate the potential phytotoxicity of various caffeine formulations under controlled environmental conditions. The optimized formulation enhanced the solubility of tank mixtures and ameliorated the negative impacts of seed treatments to germination. Our caffeine formulation provides an applicable, nonlethal alternative for managing blackbird impacts to agricultural production.     

Effectiveness of AV-1011® to reduce damage to drill-planted rice from blackbirds

We determined efficacy of AV-1011® (a 50% anthraquinone product; Arkion® Life Sciences, New Castle, Delaware) on drill-planted rice seed to reduce blackbird damage and determine residue levels of anthraquinone (AQ) in rice seeds and seedlings and in the mature rice crop under field enclosures at the University of Missouri-Delta Center farm near Portageville, Missouri. Red-winged blackbird (Agelaius phoeniceus) damage was higher for untreated than AV-1011® treated rice seedlings at assessment period 3, 15 days postplanting (F_1,141 = 15.81, P < 0.001), and at assessment period 4, 19 days postplanting (F_1,136 = 11.54, P = 0.001). Blackbird damage to AV-1011-treated seedling for assessment periods 3 and 4 was 8% and 7%, respectively, while blackbird damage to untreated seedlings during the same assessment periods was 52% and 44%. More blackbirds used untreated plots than AV-1011-treated plots during assessment periods 2–4 (F_1,17.8 = 20.02, P < 0.001). Overall concentrations of AQ on seeds averaged 5,993 µg/g or 0.59% during the test period. Concentrations of AQ in mature rice seed and plant collected at harvest averaged 1.22 µg/g and 0.10 µg/g, respectively. AV-1011 offers promise for reducing bird depredations to newly planted rice, but additional testing should be conducted to evaluate this repellent in a large-scale field setting. © 2011 The Wildlife Society.