2017 ASHS Annual Conference

Almost all commercial strawberry growers in the Upper Midwest utilize the matted row system, in which June-bearing strawberries are managed as perennial crops in straw mulch. June-bearing cultivars are characterized by short-day flower induction periods; buds are initialized in autumn before the plants go dormant, followed by flower and fruit development in the long days of the following spring. This results in a 4-6 week harvest window in June, hence the common name. Midwestern yields using this technique are low – 8,500 lbs./acre/year on average – but the short harvest window allows growers to focus on other crops throughout the rest of the summer and fall. Growing day-neutral cultivars, which can offer extended seasons and higher yields, has historically been unviable in the Upper Midwest. Poor plant performance including unreliable yields, soft fruit, lack of winter hardiness and vulnerability to disease kept these cultivars from being utilized in this region of the US for decades. However newer-release cultivars, in combination with adjusted cultural practices, allows Upper Midwestern growers the opportunity to grow day-neutral strawberries for the first time. In University of Minnesota research along with grower collaborator trials, cultivars ‘Portola’, ‘Albion’, ‘Monterey’ and ‘Seascape’ produced reliably from July to the end of October during the 2013-2016 growing seasons. When managed as annuals in a raised bed, white-on-black plastic system with low tunnel coverings, scaled yields ranged from 20,000-38,000 lbs./acre/year. It is believed that reduced weed competition from the plastic mulch in addition to reduced fungal pressure under low tunnel coverings and more vigorous genetics in the recent cultivars lead to the better adaptation of day-neutrals in Upper Midwestern climates. Ongoing day-neutral research in the Upper Midwest has grown considerably since 2013. Current projects include testing low tunnel plastic types for differences in fruit marketability and pesticide effectiveness, inoculation of plants with arbuscular mycorrhizal fungi for possible increases in annual yield, the effect of native wildflowers on pollination efficiency and fruit weight, and performance of biodegradable films as a replacement for white-on-black plastic mulch. Challenges still remain for adoption of this technique, including fears about spotted wing drosophila, tarnished plant bug, and how the extended season will conflict with farm plans that divert labor to other crops after the June-bearing season ends.