During the 2007-2009 period in IFC, Pleven (Bulgaria) a field trial was carried out with the purpose of studying the tolerance of 8 lucerne varieties to attack by Apion seniculus Kirby. It was found that the attack of weevil was the strongest at primary growth. The damaged plants varied from 21.1 to 45.8%. Attacked plants were the most in the second and third year of cultivation of alfalfa (34.1-48.4%). Apion seniculus attacked the least varieties Europe and Multifoliate lucerne. The degree of the damaged stems were respectively 9.10 and 8.16%. These varieties occupied the first two plases in the list of varieties ranging. The most sensitive were Prista 3 (20.03%), Obnova 10 (18.21%) and Pleven 6 (18.24%). The parameters that had the most influence on the degree of the damaged stems by larvae of Apion seniculus were: the rate of regrowth in the spring, respectively the height of stems (r = +0.830) and number of stems of a plant (r = – 0.703). With a good tolerance to tracked parameters were Europe and Multifoliate lucerne, which determined their phenological and morphological tolerance.
I. Nikolova, N. Georgieva