4-Aminopyridine Effectiveness in Sweet Corn Related to Blackbird Population Density

Abstract

Applying cracked corn to sweet-corn fields, with 1 percent of the particles treated with 4aminopyridine (4-AP), generally did not reduce blackbird (Icteridae) damage in Ohio, Maryland, and New York in 1974. These findings contradict results reported from tests of 4-AP treatments in localities where blackbird population densities were considerably higher than in our test localities. We hypothesize that the lack of success of this treatment in protecting sweet-corn fields in the eastern United States was due, at least in part, to low population densities and thus to low frequencies of reacting birds. We suggest that the effectiveness of 4-AP-cracked corn treatments can be improved by increasing the proportion of treated corn particles and by changing the application rate. J. WILDL. MANAGE. 40(3):564-570 Goodhue and Baumgartner (1965) described a chemical, 4-aminopyridine (4AP) that causes certain flocking birds that ingest it (e.g., redwings [Agelaius phoeniceus], grackles [Quiscalus quiscula], and starlings [Sturnus vulgaris]) to act before death in a manner (squawking, erratic flight) that repels flocks of these species. Because blackbirds are species so affected by 4-AP, the U.S. Fish and Wildlife Service conducted research from 1962 to 1969 to develop a treatment form of the chemical that would provide growers of field corn measurable protection from blackbird damage without adverse effects on other wildlife. In tests in South Dakota (De Grazio et al. 1972) and Ohio (Stickley et al. 1972, 1976), blackbird damage to field corn was reduced when 1.1-5.5 kg cracked corn/ha (1-5 lb/acre) with 1-3 percent of the corn particles treated with 4-AP was applied to fields of ripening corn. The frequency of application of cracked corn during the 15to 30-day period when ripening field corn is vulnerable to blackbird damage ranged from 1 to 7 times per field in these tests. In 1972, the U.S. Environmental Protection Agency issued a registration label for Avitrol FC Corn Chops-998 (reference to trade names does not imply endorsement of commercial products by U.S. Government) for control of blackbird damage to field corn. The label specifies the product form of 4-AP to be cracked corn (usually #6 size) with 1 percent of the corn particles treated with 3 percent (by weight) 4-AP, and a product application rate of 1.1 kg/ha (hereafter we shall refer to the registered product as FC-99 with the understanding that any reference to an FC-99 treatment indicates that the application rate is 1.1 kg/ha). The label further specifies that FC-99 is applied to fields in 20-m-wide swaths alternated with 40-m-wide untreated swaths with subsequent applications made on untreated swaths. FC-99 is not applied closer than 15 m to field edges. No limit is set on the number of applications per field per season, but logistics and economics generally set the level at 3 to 4 applications at regularly-spaced intervals (usually 4-7 days). Applicators must be trained and supervised by governmental agencies. Almost all fields are treated by air. Hand broadcasting is not permitted. A logical extension of the use of FC-99 is for protection of other grain crops. In 1974, we tested the efficacy and safety of 564 J. Wildl. Manage. 40 (3):1976 This content downloaded from 207.46.13.169 on Sun, 03 Jul 2016 06:18:17 UTC All use subject to http://about.jstor.org/terms 4-AP EFFECTIVENESS IN SWEET CORN Dolbeer et al. 565 FC-99 treatments in reducing bird damage to sweet corn in Ohio, Maryland, and New York. Our purpose was to evaluate FC-99 under a commercially realistic treatment schedule in a normal agricultural setting where blackbird damage to sweet corn was considered a serious problem by local farmers. We gratefully acknowledge the following people for assistance in the tests: J. E. Forbes, A. J. Godin, J. T. Linehan, B. Meanley, L. C. Gibbs, M. E. Laderach, S. B. White, D. E. Steffen, K. M. Simpson, R. V. Bodkin, and D. G. Meeker.