A mechanical barrier against apple scab

Abstract: In the frame of the French Ecophyto Plan aimed to reduce the number of treatments in agriculture, protecting apples against rain with plastic covers on the top of the trees was tried from 2010 by Ctifl at its site in Lanxade in the South-West of France. Different types of rain cover were studied. The effectiveness was very high on cvs. Braeburn and Gala, reaching 100% on fruits, without any additional use of fungicides, even in presence of some scab on the shoots. In a newly planted orchard, with a more susceptible variety, an outbreak of scab occured under the covers. The different possible causes were analyzed, through measuring climatic data, trapping spores and running the apple scab warning program RIMpro. The microclimate under the rain covers seemed to be favorable to powdery mildew, woolly aphids and unfavorable to storage diseases. The system may be improved with a few fungicide treatments to avoid powdery mildew and during the most severe scab infections.