Row Covers as a Weather Risk Management Tool in Plasticulture Strawberries

The 2014 winter season in the Mid-South proved to be one of the most challenging winters for management of cold weather extremes since strawberry plasticulture was introduced in this  region in the early 1980s.  Though temperatures below -20 C were not experienced this past winter (as occurred in January 1985), many strawberry growing areas in North Carolina experienced temperatures of just below -17.7 C on 7-Jan-14. Despite plants bieng fully dormant at the time of this arctic clipper in early January,  significant crown injury occurred in both Chandler and Camarosa plants that did not have winter row cover protection.  The freeze-injured plantings were about 10 days later in crop ripening in spring 2014 than plantings that had row cover protection.   A second 'arctic clipper' occurred in the Mid-South over the period of 26-Feb-14 to 1-Mar-14, and minimums were as low as -10 C in the NC piedmont.  At this juncture, the crop had broken dormancy and was in the pre-bloom period.  With row cover protection during this second arctic clipper in late February, growers were able to save non-emerged flower buds that were still inside crown, but a high percentage of newly emerged 'tight' buds were killed at -10 C.  Under the windborne freeze conditions of 26-27 Feb, a  small number of growers attempted a relatively new technique of using sprinkling in conjuction with row covers, and this approach proved to be very successful for saving all flower buds stages (non-emerged and emerged) as well as the so called 'popcorn' stage (just before open blossom). The author will describe a relatively new weather tool called the 'Row Cover Optimizer' that provides generally accurate two week weather forecasts for strawberry growers in a 4-state region (VA-NC-SC-TN).  With this tool, growers can better anticipate when their row covers may need to be 'ON'  for freezes, and they are also advised of  mid-winter ‘warm up’ periods when covers need to be 'OFF.'   Whenever average daily temperatures in January are 4-5 C above normal, and this happens over a consective 2-3 day period, there is greater risk of the crop breaking dormancy underneath the covers.  Smaller strawberry plasticulture growers (< 4 ha) with access to family and/or local labor are generally more successful in making timely adjustments in winter row cover usage according to changing weather conditions than are larger growers who depend on a migrant labor force that is unavailable until early spring.