CONTROL OF COLLETOTRICHUM-ACUTATUM IN STRAWBERRY UNDER LABORATORY, GREENHOUSE, AND FIELD CONDITIONS

Various fungicides and a heat treatment were assessed for their abilit y to control strawberry anthracnose caused by the fungus Colletotrichu m acutatum under laboratory, greenhouse, and field conditions. The eff ective dose causing 50% inhibition of mycelial growth (ED50) was 30.5, 12.2, 0.2, 0.15, 0.05, 0.07, and 0.05 mu g/ml for the fungicides folp et, captan, propiconazole, difenoconazole, combined prochloraz-Zn/folp et, prochloraz-Zn, and prochloraz-Mn, respectively. In laboratory expe riments, infection in segments of strawberry runners treated with proc hloraz-Zn reached 60%, which was significantly reduced as compared to combined prochloraz-Zn/folpet (90%), captan, folpet, and water control s (100%). In the greenhouse, numbers of naturally infected transplants killed were significantly reduced by all fungicides and the heat trea tment (5 min at 49 degrees C) as compared to the non-treated control. Prochloraz-Zn was the most effective chemical control treatment but di d not differ significantly from the heat treatment. In field experimen ts conducted during 1995 and 1996, numbers of naturally infected straw berry transplants killed were significantly reduced by all fungicide t reatments relative to the nontreated control. Percent reduction of tra nsplant mortality in the field was 93.3, 93.1, 66.7, 37.7, and 29.1 fo r prochloraz-Mn, prochloraz-Zn, combined prochloraz-Zn/folpet, propico nazole, and difenoconazole, respectively.