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The Influence of Aphid Infestation during the Hop Growing Season on the Quality of Harvested Cones
F. Weihrauch, A. Baumgartner, M. Felsl, K. Kammhuber, A. Lutz

The influence of aphid infestation on the quality of harvested hop cones was researched during four years from 2008 to 2011. The cone infestation of altogether 60 hop gardens (2011: 16 gardens) and five cultivars ? Hallertauer Magnum, Hallertauer Tradition, Herkules, Spalter Select (2008-2010) and Perle (2011) ? was assessed in three plots, respectively (untreated control, one insecticide application, practice), during the growing season by the use of modified Berlese funnels. In three gardens of each cv. an experimental harvest was conducted annually, determining yield, cone infestation, and other quality parameters. The registered infestations ranged from nil to a maximum of 50.5 aphids per cone. High aphid infestation was able to cause a significant loss of yield and alpha acids in several cases in 2009 and 2011, whereas in 2008 even severe infestations did not have according similar impact. During 2010, almost no aphid infestation was detected at all. However, investigated quality parameters other than the bitter acids ? cohumulone, colupulone, xanthohumol and hop oils or their constituents (e.g. linalool, humulene, myrcene) ? were never affected by high cone infestation. It is concluded that these quality parameters are unlikely to be impaired by aphid infestation of the hop plant.

Descriptors: hop entomology, damson-hop aphid, hop quality, alpha-acid content

BrewingScience - Monatsschrift fr Brauwissenschaft, 65 (July/August 2012), pp. 83-90