A review of strawberry under protected cultivation: yields are higher under tunnels than in the open field

Strawberries are grown under tunnels to protect the plants from cold, frosts, rain, and fruit diseases. A review was conducted to determine the performance of plants under plastic tunnels. Information was collected on yields and fruit weight under tunnels and in the open field (n = 133 experiments) and on environmental conditions in the two areas. In a global analysis, plants under tunnels had higher relative marketable (Tunnel/Open = 1.34 ± 0.76) and total yields (Tunnel/Open = 1.30 ± 0.83) than those in the open (p < 0.001). In contrast, fruit weight was similar in the two growing areas (Tunnel/Open = 1.04 ± 0.22) (p = 0.094). Relative marketable yields (Tunnel/Open) were similar in plants in Northern and Southern Europe, and in Northern and Southern America (p > 0.05). Relative marketable yields were similar in areas with cool or cold winters or with spring/summer or winter/spring production seasons, and under low or high tunnels (p > 0.05). Lower yields under tunnels were associated with low light levels and high temperatures under the plastic and a higher incidence of powdery mildew. The use of tunnels under global warming will require attention to ventilation under the covers.