Viability of a prediction system for tomato late blight in the integrated production of tomato in Caçador, Brazil

An alert system for tomato late blight was validated in an Integrated Production System (IP) in the 2006-2007 and 2007-2008 season in Caçador, Santa Catarina State, Brazil. The late blight is a destructive disease and demands 25 or more fungicide sprayings per season in a Conventional Production (CP) System. For the CP area, the chemical control was according to the growers' production systems and consisted of weekly sprays soon after planting. For the IP area, the criterion for the first fungicide spray was according to Machardy (1972) and for subsequent ones according to Wallin (1962), when the disease severity values (DSV) reached eight points. There was a decrease on the fungicide application in the IP, not only in the number of fungicide sprays (23-28%) but also in the amount of active ingredient (34.5-60.9%). Fungicides classified as highly toxic (class I) were not used in IP. There were no significant differences among the use of alert system on IP and the weekly schedules on CP with regard to final disease severity in the 2006-2007 season, but it was significantly lower in the second trial on plants for IP area. The IP system significantly increased tomato yield (7.6-25.5%) compared with CP system and reduced fungicide cost up to US$539/ha. The use of alert system could be a valuable and affordable tool in managing tomato late blight in Integrated Production of tomatoes in Caçador.