Typically, for the open-field annual plasticulture production system, the spring strawberry crop peaks in May in Southeastern Virginia. High tunnel production could provide an early extended season for locally grown produce and could potentially earn a higher market value for the crop. These additional sales could help with offsetting the costs of high tunnel construction.
Nonmarketable yield inside the high tunnel was due to animal bites; diseases including botrytis (Botrytis cinerea) and anthracnose (Colletotrichum acutatum); damage from mollusks, mites, and insects; small fruits (<10 grams in weight); and misshapen fruits. About 30% of the fruits in our study on a per-plant basis were damaged by animals. Red fox (Vulpes vulpes), raccoons (Procyon lotor), and birds entered the high tunnel and caused damage by feeding on fruits. If animal entry can be better controlled, growers can expect a higher marketable yield. Raccoons and foxes could be a potential challenge, particularly in urban areas where food availability and food choices are scarce for these animals during winter months. For subsequent studies in the high tunnel, we installed an electric fence around the perimeter of our study area to minimize animal traffic. A bird net has also been installed along the side openings of the tunnel to prevent birds from entering the tunnel when the side curtains are open. Additionally, we have installed shade cloth on the openings of the garage doors using a wiggle wire to prevent birds from entering the tunnel when garage doors are rolled up.
Among diseases, botrytis was the major issue observed in the cooler and cloudy months of January, February, and March. In April, both botrytis and anthracnose contributed to the nonmarketability of fruits in the high tunnel. As air temperatures increased in May and June, anthracnose fruit rot was the prevalent disease issue.
Additional information on these diseases, including symptoms, disease cycles, and management practices, can be found in the following publications from North Carolina State Extension:
Landscape fabric was used to keep the weeds in the furrows in check. Despite the use of the fabric, occasional hand weeding was necessary in furrows, ends of beds, and planting holes in order to reduce weed density. Garden slugs (Arion hortensis) and snails (Cornu aspersum) were found feeding on strawberry leaves and fruits, making irregular holes on the foliage and rendering the fruits nonmarketable. This was a particular challenge in the winter months and early spring. The use of landscape fabric created a moist environment in the furrow space that appeared to promote their reproduction. To control slugs and snails, we used slug and snail bait (1% iron phosphate) at 1 teaspoon per square yard around the planting holes, Sevin at 3/8 ounce per gallon of water, and slug traps (a plastic water bottle with a sugar-water mixture).
Twospotted spider mites (Tetranychus urticae) could be a potential problem for high tunnel cultivation due to dry conditions in the structures. Spider mite webs can be found mainly on the undersurface of the leaves and fruits. If heavily infested, spider mites can cause defoliation and plant death. Additional information on spider mite biology and control can be found at www.virginiafruit.ento.vt.edu/Strw2Spotted.html.
Sawfly larvae (Empria spp.) were another pest found feeding on the leaves of the tunnel-grown plants in February and March. Green larvae were found feeding on the leaves and usually did not require chemical treatment. Additional information on sawflies can be found on the website of University of Minnesota Extension: https://extension.umn.edu/yard-and-garden-insects/sawflies#using-pesticides-1113863.
Economic Considerations
A grower’s decision on whether or not to grow strawberries in a high tunnel would be determined by the profitability of strawberry production. More elaborate variety evaluation trials at the Hampton Roads AREC in the 2019-20 growing season included both ‘Ruby June’ and ‘Sweet Ann’, and we plan to address this question of profitability for Virginia growers interested in strawberry production. This publication highlights new varieties showing promising results in our high tunnel trial and describes some of the challenges and opportunities for high tunnel production we identified through this study.
Summary
‘Sweet Ann’ and ‘Ruby June’ were the two cultivars that performed well in our trials. Growers and consumers like ‘Ruby June’ for its berry flavor and ease of picking as compared to other standard varieties like ‘Chandler’. We were able to identify challenges as well as opportunities for strawberry production in the high tunnel environment. Challenges included a lack of preparation for a slightly different spectrum of pests, including insects, mollusks, and twospotted spider mites, as compared to open-field production. Production in the high tunnel also requires detailed weather monitoring of precipitation events, wind speeds, and high temperatures to better manage ventilation in the tunnel, which has implications on fruit disease incidences and flowering and fruiting capacity of the crop plant. Opportunities include season extension of strawberry fruit production, better management of labor at the farm during rain events, and improved fruit quality (e.g., improved fruit firmness and fewer fruit rots due to less rain exposure on the plant canopy).
Based on the information presented, we cannot say if high tunnel strawberry production is profitable. However, for growers interested in strawberry cultivation in a high tunnel, the following regional resources will be useful:
Acknowledgments
This study was funded in part by Lassen Canyon Nursery. The authors would like to thank Jillian Rajevich, Mikel Manchester, Andrew Hall, Ellen Owen, and Zachary Landis for their assistance with this study. Thanks to Sanjun Gu, Chris Mullins, M. Watson Lawrence Jr., and Kari Sponaugle for reviewing this publication prior to release.
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