PERFORMANCE OF THE PSEUDOMONAS-CHLORORAPHIS BIOCONTROL AGENT MA-342 AGAINST CEREAL SEED-BORNE DISEASES IN-FIELD EXPERIMENTS

The bacterial biocontrol agent Pseudomonas chlororaphis, strain MA 342 , was tested for activity against a number of cereal seed-borne diseas es in a total of 105 field experiments carried out at different locati ons in Sweden during the years 1991-1996. Bacterial liquid culture was directly applied to pathogen-infested seeds of barley, oats, wheat an d rye without additives. The seeds were then dried and sown in field t ogether with fungicide-treated and untreated seeds used as controls. T he bacterization controlled seed-borne diseases caused by Drechslera ( Pyrenophora) graminea, D. teres, D. avenae, Ustilago avenae, U. hordei , and Tilletia caries, as effectively as guazatine + imazalil, and the se effects were consistent over the years and over varying climatic zo nes. Diseases caused by pathogens like U. nuda, soil-borne I: caries a nd I: contraversa were not controlled and the bacterization gave less than full effect against diseases caused by Microdochium (Fusarium) ni vale, and Bipolaris sorokiniana (Cochliobolus sativus). Bacterized see ds could be stored dry for at least two years without losing the disea se suppressing effect of the bacterial treatment, when tested in the f ield.