Influence of Spring Frost and Blossom Weevil Damage on Strawberry Yield Formation

Depending on the year, strawberry blossoms are damaged by blossom weevil and spring frost. Both damages depend largely on the cultivars, its time of flowering and frost tolerance of blossoms, or blossom weevil preference of cultivar and temperatures before and during flowering. Cv. 'Senga Sengana' was chosen for the study because it has been extensively grown in northern European countries for a long time and in all cultivar evaluation trials in Estonia it has been used as a control. Data were gathered over the eight years period (1999-2007). The data from 'Senga Sengana' were compared to the data obtained from 14 strawberry cultivars on blossom weevil damage in 2005 and 2006 and on spring frost damage in 2006. The results reveal the blossom weevil preference of cultivars. Blossom weevil prefers cv. 'Venta' most of all, cv. 'Sega Sengana' gets less damage. The damage of blossom weevil is most severe in years when average temperatures in May are over 10°C and there are no severe spring frosts. The damage of blossom weevil is extensive in years when the number of blossoms is low (with 'Senga Sengana' in 2003) 'Senga Sengana', being a late cultivar, does not suffer much from spring frosts. Over the nine-year test period only in two years (2002 and 2004) its blossoms had remarkable damage from spring frosts. In 2006 cultivars 'Gerida' and 'Wega' suffered most from spring frosts. With cv. 'Gerida' the damage rate was high partly due to low number of blossoms.