Tolerance comparison of 33 potato cultivars to the Colorado potato beetle, Leptinotarsa decemlineata (Col.: Chrysomelidae), in the field conditions in Naghadeh, west Azerbaijan

Colorado potato beetle, Leptinotarsa decemlineata (Say), is the most important defoliating pest of potato throughout the world and Iran which considerably reduce crop yield. In this study tolerance of 33 cultivars of potato were compared during 2007-2008 in the field conditions. Experiment was carried out in both years in two trials, infested and non infested plots and arranged based on a randomized complete block design. In infested plots, each plant was infested by 40 medium larvae (second and early third instars) 15 days prior to the blooming of plants. Non-infested plots were kept pest-free by chemical and mechanical control methods. At the end of the season, defoliation and yield loss in infested plots were determined and compared with non-infested plots in each cultivar. Cluster analysis of cultivars was performed with MINITAB15 statistical software using UPGMA procedure based on Euclidean distance. Combined analysis of variance of tolerance data in 2007 and 2008 showed significant differences among the cultivars (P < 0.01). Moreover, for all studied traits reciprocal effect of cultivar × year was significant (P < 0.05). Cluster analysis based on defoliation and yield loss in two experimental years showed that cultivars “Santana”, “Satina”, “Bridjet” and “Cardinal” had the highest tolerance to the Colorado potato beetle. Significant positive correlation was observed between yield loss and defoliation traits in two years of study (P<0.01).