In the "Entre Douro e Minho" region, in northern Portugal, we studied the use of two types of structures, tunnel and bitunnel, with different types of ventilation, traditional and permanent respectively, with tomato spring crops in 1997 and 1998. Internal climate, crop response and Botrytis incidence were analysed. The average air temperature was similar in both greenhouses during the day. However, during the hottest days, the larger windows area and the superior ventilation of the bitunnel led to a reduction of the maximum air temperatures. The relative humidity was 5 to 10% lower in the bitunnel relatively to the tunnel. This reduction resulted from the permanent ventilation during the night and the more efficient ventilation in the bitunnel. In both kinds of structures, we managed to reduce the number of Botrytis treatments in a significant way, compared to those made by the commercial growers. The number of treatments was equal in both greenhouses to evaluate the incidence of Botrytis cinerea. The crop response did not show significant differences between greenhouses, namely the total production, but it was higher in the bitunnel in 1998, for the grades Extra and Extra + 1. The number of fruits with grey mould was slightly higher in the tunnel.
