Control of Colletotrichum acutatum in strawberry under laboratory, greenhouse, and field conditions

Various fungicides and a heat treatment were assessed for their ability to control strawberry anthracnose caused by the fungus Colletotrichum acutatum under laboratory, greenhouse, and field conditions. The effective 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 folpet, captan, propiconazole, difenoconazole, combined prochloraz-Zn/folpet, prochloraz-Zn, and prochloraz-Mn, respectively. In laboratory experiments, infection in segments of strawberry runners treated with prochloraz-Zn reached 60%, which was significantly reduced as compared to combined prochloraz-Zn/folpet (90%), captan, folpet, and water controls (100%). In the greenhouse, numbers of naturally infected transplants killed were significantly reduced by all fungicides and the heat treatment (5 min at 49 degrees C) as compared to the non-treated control. Prochloraz-Zn was the most effective chemical control treatment but did not differ significantly from the heat treatment. In field experiments conducted during 1995 and 1996, numbers of naturally infected strawberry transplants killed were significantly reduced by all fungicide treatments relative to the nontreated control. Percent reduction of transplant mortality in the field was 93.3, 93.1, 66.7, 37.7, and 29.1 for prochloraz-Mn, prochloraz-Zn, combined prochloraz-Zn/folpet, propiconazole, and difenoconazole, respectively.