Impact of extreme temperature and/or ultraviolet radiation on grape cultivation

Polyethylene film is used to cover grape vines in Victoria in Southeast Australia. The films vary in thickness from 100 to 250 micrometers and contain titanium dioxide and UV stabilization at levels selected to allow for some light transmission while protecting the film from breakdown. Expected lifetimes for the films are 1 - 4 years. Field reports in the summer of 2003-2004 indicated a number of instances in which the film covers had burned plant buds. Anecdotal reports indicated the extent of this problem was significantly more severe than in the past half dozen years and suggested the summer temperatures and/or surface ultraviolet (UV) radiation levels may have been more extreme than in recent years.

Although there is no UV monitoring station in this grape growing region, forecast values for the noon-time, cloud-free, UV Index in the region prepared by the Australian Bureau of Meteorology suggest the surface UV radiation may have been more intense in the summer of 2003-2004 (particularly in Dec 2003) than in any previous summer since 1997. Meteorological data for the grape growing region (e.g., cloud cover, visible radiation flux, temperature), UV radiation measurements made at stations in Southeast Australia, and total ozone column data will be examined to quantify whether conditions in the summer of 2003-2004 were more extreme than in recent years and, if so, to determine what atmospheric phenomena are most likely responsible.