Date of this Version
Paper presented at the 34th National Sunflower Association Sunflower Research Workshop, Bismarck, North Dakota. (2012).
Blackbirds in the northern Great Plains aggregate in large flocks that feed on ripening crops, especially sunflower. Damage to the sunflower crop begins when the achenes reach the “milk” stage, which is in mid-August to late August. Direct economic losses from bird damage to sunflower probably exceed $5 million, annually (Peer et al., 2003). Growers incur additional costs trying to protect their crop from blackbirds. Growers can use several techniques singly and in combination to defend crops, including firearms, propane cannons, pyrotechnics, and fragmentation of dense cattails (Typha spp.). Except for cattail management with aerially applied glyphosate, most methods are time consuming, costly, and produce inconsistent results, particularly when used on large fields with many birds (Linz et al., 2011). Aerially applied feeding repellents may help protect sunflower in large fields, especially if used with other methods in an Integrated Pest Management Program (Linz et al., 2011). However, sunflower producers and USDA researchers have both reported inconsistent results with the only two repellents registered for use on ripening sunflower, Birdshield® and Flock Buster® (Linz et al. 2011).
Results from cage tests on blackbirds have indicated that chemical repellents can be very effective. A particularly promising candidate is 9,10 anthraquinone (Avery and Cummings, 2003). The anthraquinone (AQ) compound is classified as a biopesticide. AQ is naturally occurring and can be found in animals, plants, and bacteria. These organisms use AQ for chemical defense against predation, parasitism, and other types of attacks (e.g., herbivory). It has been tested and found to be an effective seed treatment for repelling granivorous birds from newly planted fields of canola, rice, corn, and sunflower (Avery and Cummings, 2003; Werner et al., 2011). The patent holder, Arkion™ Life Sciences LLC (551 Mews Drive Suite J., New Castle, Delaware, 19720, USA), has recently applied for a full national registration (EPA FIFRA Section 3) to use AQ repellent on corn seeds.
Several studies using caged blackbirds have consistently shown that feeding rates are reduced by ≥80% with AQ treatments, especially with sunflower. Werner et al. (2011) reported that AQ repelled COGR and RWBL confined within enclosures in fields of standing sunflower. Results from field trials in ripening rice were, however, equivocal (Avery and Cummings, 2003). For example, AQ protected field plots of ripening rice in Louisiana for 7 days following aerial application, but similar tests on wild rice in California yielded no treatment effect. The birds have to learn that AQ cause gastric distress by eating it, and its lack of effectiveness in wild rice was attributed to an influx of new, AQ-naive blackbirds at the study site. Of course, it is not unusual during the process of field-testing to have some inconclusive field trials. Thus, we remain committed to our immediate goal of expanding research on AQ to protect ripening fields of sunflower. This product could represent a major advance in blackbird damage management if repellency can be maintained at field application rates, with the caveat that residue levels at harvest meet the yet to be proposed food tolerance guidelines. We are now at the phase of testing that requires us to develop effective techniques for aerial and ground applications of a 9,10-anthraquinone product (Avipel®, Arkion™ Life Sciences; New Castle, DE).