BIOLOGICAL-CONTROL OF BREVICORYNE-BRASSICAE WITH THE PARASITIC FUNGUS VERTICILLIUM-LECANII IN THE LABORATORY AND IN THE FIELD

Different isolates of the fungus Verticillium lecanii (Zimm.) Viegas are pathogenic for the aphid Brevicoryne brassicae. Experiments in growth chambers indicated, that a control of the insects with conidia or blastospores of V lecanii alone is not sufficient. The water suspension of spores needs to be mixed with polysaccharides and detergents (2 % soymeal, 0,5 % carboxymethylcellulose, 0,5 % sodium alginate and 0,02 % TWEEN 20) to be effective. Experiments in the field were performed in small experimental plots during three subsequent years. One week after inoculation, the mixture of blastospores with polysaccharides reduced the number of aphids up to 80 %, a mixture of blastospores with 0,5 % phospholipid reduced the aphids by 58 to 85 %. Application of the pyrethroid-containing product SPRUZIT reduced the number of aphids by 87 % and the phospholipid alone by 41 % to 59 %. In two large field experiments with cabbage plants (Brassica oleracea var. capitata), which were performed under practical conditions, similar results were obtained. Compared with the control plants, which were treated with phospholipid alone, the number of aphids was reduced by about 70 %, 8 days after the application of a mixture of blastospores with 0,5 % phospholipid Nat 1358. At this date, the application of the phospholipid reduced the number of aphids by 30 %. The results show that in the field a control of aphids with V. lecanii is possible if the spores are mixed with additives such as polysaccharides or phospholipids. The phospholipids, used alone, also may be applied to control aphid populations.