Tolerance of Strawberry Cultivars to Oxyfluorfen and Flumioxazin Herbicides

Abstract

Herbicides can be an excellent supplemental treatment in cases where soil fumigant treatments alone fail to control weeds during the growing season or in situations where fumigants cannot be used as a result of regulatory restrictions. Previous studies have shown that oxyfluorfen and flumioxazin can provide satisfactory weed control in bedded strawberry (Fragaria ×ananassa Duch.) production. However, we need to know if tolerance to herbicides is uniform across strawberry cultivars under California conditions. The objective of this study was to determine if tolerance to oxyfluorfen and flumioxazin herbicides varied among strawberry cultivars. Trials were conducted in the 2007–2008 and 2009–2010 growing seasons at Salinas, CA. Treatments included an untreated control; pre-plant applications of flumioxazin at 0.07, 0.11, and 0.21 kg·ha−1 a.i.; and oxyfluorfen at 0.14 and 0.28 kg·ha−1 a.i. The entire trial was fumigated with an emulsified formulation of 60% 1,3-dichloropropene + 32% chloropicrin applied at 281 L·ha−1 by drip injection to all plots. Eight strawberry cultivars were included in the trial in the 2007–2008 growing season, and nine cultivars were included in the 2009–2010 growing season. In both growing seasons, slight to no crop phytotoxicity was observed. In the 2007–2008 growing season, several strawberry cultivars including ‘Albion’, ‘Festival’, ‘211G51’, ‘Palomar’, ‘Plant Sciences 5298’, and ‘Ventana’ had smaller crop plant canopy diameter as compared with the control when treated with 0.21 kg·ha−1 a.i. of flumioxazin. Compared with the control, flumioxazin at 0.21 kg·ha−1 a.i. reduced crop diameter for ‘Plant Sciences 4634’, ‘Plant Sciences 5298’, ‘San Andreas’, and ‘Ventana’ in the 2009–2010 growing season. In the 2007–2008 strawberry-growing season, none of the herbicide treatments reduced fruit yield compared with the control. In the 2009–2010 growing season, in seven of the nine cultivars, there were no significant differences in yield among treatments. For ‘Palomar’ strawberry, yields in plots treated with flumioxazin at 0.11 and 0.21 kg·ha−1 a.i. were significantly lower than the untreated control. With the exception of flumioxazin at 0.21 kg·ha−1 a.i., these herbicides are safe to use and can be incorporated in strawberry production practices for the cultivars tested to achieve satisfactory weed control over the growing season.