Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu and Emmalea Ernest, Associate Scientist – Vegetable Crops; emmalea@udel.edu
As the climate is expected to become wetter with more extreme rainfall events, losses of fruit crops to excess rain will become more of a concern.
A high tunnel structure may be used as a rain shelter to cover plants during fruit formation and development. Multi-bay “European” style tunnels are most commonly used as rain shelters covering from ½ acre to several acres. Rain shelters are used extensively in high rainfall areas around the world to protect rainfall sensitive crops such as strawberries. Covers may be used for the whole season or just for the fruiting period.
Rainshelters are also use for other fruits, such as cherries, which are susceptible to cracking. Some fruits crack from absorbing water through the skin of the fruit when they are ripe or near ripe, others crack with excess water in the root zone, and there can be a combination of the two processes. Rainshelters control both types of fruit cracking. Rain shelters also reduce foliar wetting and rain splash and therefore can reduce fungal and bacterial diseases considerably if left on for the whole growing cycle.
While a high tunnel will serve as a rain shelter, less expensive low-tunnel structures can also be used that have a plastic cover over hoops from 2 to 6 feet tall.
Rain shelters are also useful for fruit crops such as cherries, strawberries, brambles, grapes, and blueberries. Specialty melons prone to cracking will also benefit from the use of rainshelters.
The Tunnel Berries Website (https://www.tunnelberries.org/) has information on materials and suppliers for high and low tunnel structures that can be used as rain shelters.
Rain cracking usually occurs where water accumulates and remains on cherries. Cracks typically appear at the pedicel (3 left columns), the suture (4th column) and the stylar end (last 2 columns) where droplets of water hang on fruit (from California Agriculture 51(5):35-40)
Dwarf cherries being grown under a rain shelter.
Low tunnels can also serve as rain shelters.
Low tunnels protect strawberries from disease.