Survival of Colletotrichum acutatum in Soil and Plant Debris of Leatherleaf Fern

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Abstract
Leatherleaf fern anthracnose is incited by a new pathotype of Colletotrichum acutatum. Fern anthracnose appeared in Florida in 1993, has spread rapidly, and produces losses that approach 100% in some ferneries. To help develop recommendations for control and management of fern anthracnose, the survival of the pathogen in soil and diseased plant material and on clothing was investigated in laboratory and field experiments. Survival of conidia, sclerotia, and conidia in infected leaf debris was studied in soil maintained at five soil moisture levels. Survival of conidia and sclerotia declined rapidly under moist conditions (≥12% moisture, vol/wt), but under dry conditions, viable conidia could be detected up to 12 months after incorporation into soil. Similar results were obtained in field experiments in which infected leaf debris was buried in soil. Viable conidia were recovered for up to 3 months in leaf debris stored under laboratory conditions. Conidia applied to denim fabric were recovered up to 5 weeks after application. This indicated that contaminated clothing could transport conidia effectively within and between ferneries. Inoculating ferns with dilutions of conidia demonstrated that at least 100 conidia per ml is required to infect and colonize leatherleaf fern leaves. This threshold provides an estimate of levels of conidia populations likely to result in disease and levels that sanitation or cultural practices must exceed to be effective management methods.