Organic apples are difficult to grow in the Midwest because spring and summer rains promote diseases that are difficult to control using organic methods. Fungal and bacterial diseases damage leaves, defoliate trees, and blemish fruit. One way to control diseases is to grow the apples in plastic-covered “high tunnels” – unheated greenhouses.
Clear-plastic film over the tunnels blocks rainfall, keeping foliage dry and preventing disease. Inside the tunnel, drip irrigation supplies water to plant roots. High tunnels are commonly used to grow vegetables, berries and flowers in Wisconsin.
At Two Onians Farms, they grow two acres of organic apples outdoors, as well as other fruits. "We keep diseases in check outdoors by growing disease-resistant varieties, pruning, and using organically-approved sprays when needed. But we were interested in trying tunnels as an alternative," says Chris McGuire with the company. "We decided to try raising dwarf apple trees in high tunnels and received a U.S. Department of Agriculture-Sustainable Agriculture Research and Education Farmer-Rancher grant to experiment."
"Looking at our numbers, it would be difficult to recoup the cost of constructing the tunnels by growing apples in them. The varieties we trialed varied a good deal in yield and heat tolerance, and it would be essential to plant high-yielding, heat-tolerant varieties."
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