The following is from Eric Hanson and Katherine Hanson, Michigan State University Extension, Department of Horticulture.
National demand for fresh raspberries and strawberries is growing, but most berries purchased in Michigan are grown in other states or countries. Growers in Michigan and other Midwestern states can produce outstanding berries, but producing reliable yields and consistent quality is sometimes challenged by our cold winters and short, humid growing seasons.
Protective structures, such as high and low tunnels, can mitigate these climatic limitations, but selecting the type of structure and plastic film cover is complicated by the enormous array of products available, and tunnels represent added risks and costs.
TunnelBerries is a seven-state research and extension project designed to provide growers with the knowledge needed to expand raspberry, blackberry and strawberry production in the Upper Midwest and Northeast U.S. with the use of protective structures or "tunnels." Work began in 2014 and we have made significant progress on several aspects of tunnel production.
One significant effort is on the use of low tunnels to produce day-neutral strawberries late into fall. Another topic is raspberry and blackberry production in high tunnels. Here we have learned raspberry yields can be increased substantially by double cropping; fruiting on one-year primocanes and second-year floricanes.
Another effort is to understand and describe the benefits and drawbacks of different tunnel plastics. Plastics now on the market can screen out specific wavelengths of light that influence tunnel temperatures as well as potentially alter pesticide longevity, insect populations and even fungal pathogens. Efforts to understand these effects are underway.
Growers and Extension educators interested in learning more about berry culture in tunnels, or tunnel and plastic types, should visit the TunnelBerries (www.tunne leberries.org/) website and TunnelBerries Facebook page (www.facebook.com/tunnelberries/).