Influential Factors upon the Occurrence and Evolution of Late Blight (Phytophthora infestans) on some Potato Varieties 2 Cultivated in Barsa Land

Late blight caused by Phytophthora infestans is one of the most devastating diseases of potato. The farmers controll the disease using a lot of fungicides, spraying between 8-16 times during the season. Field trials were carried out to the National Institute of Research and Development for Potato and Sugar Beet Brasov during the years 2014 – 2016. It was used a complet randomized block design with four replicates. Planting was made in 24 th 1 March 2016 and in 31 March 2017. In all cases, cultivation and maintenace was in line with current good agricultural practice. In the three years tacking into study late blight appeared relatively early due to favorable climatic conditions.The assessment used a key on the whole plant. It assess the overall amount of necrotic tissue per plant on a scale from 1 (resistant) to 9 (highly susceptible). In 2014 the first appearance of late blight was registered on 17 June, in 2015 in 1 July and in 2016 in 31 May. The main aim of this research was to test the influence of two different densities (53300 plants/ha and 44400 plants/ha) and two different late blight control technologies (using on side only contact fungicides - TECH1 and on the other side systemic and contact fungicides -TECH2) on three most cultivated varieties (Riviera, Christian and Roclas).