Control by seed dressing of leaf weevils of the genus Sitona (Col: Curculionidae) feeding on sprouting alfalfa

Abstract

In tests with artificial infestation of alfalfa by leaf weevils in the greenhouse and also in small-plot trials with natural infestation of sprouting alfalfa it was found that without protection alfalfa is seriously damaged by leaf weevil feeding. After evaluation of the feeding damage by weevils, the damage to plants in the untreated plot was classed as 3rd, 4 th and 5th degree on a five-level scale. Plant growth was seriously restricted and in warm and dry weather plants may die. The results demonstrate that in both kinds of trials the pre-sowing treatment of alfalfa seed significantly reduces the feeding of leaf weevils on sprouting alfalfa. No negative effects of insecticidal seed dressing on germination energy and germination were observed. On the basis of the three-year trials, the dressing insecticides Cruiser 350 FS (active ingredient thiamethoxan) and Elado 480 FS (active ingredients beta-cyfluthrin and clothianidin), both at a dose of 201/t, can be recommended as an effective method to protect alfalfa against leaf weevils.