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Pennsylvania Flower Growers #282


The stub dieback phase of Fusarium stem rot is a serious disease of carnation (5). The same fungus also causes various stem rot and head or ear rots of corn and cereals. The fun gus has an asexual stage known as either Fusarium graminearum (2) or F. roseum 'Graminearum (8) and a sexual stage known as Gibberella zeae. Although the disease is often present in commercial carnation greenhouses, it was only recently that the perithecia of G. zeae were found on carnation (4). Ascospores formed in the perithecia are ejected into the air and thus provide an air-borne stage of the fungus. Initial data ac quired in a greenhouse containing carnation plants showing a severe outbreak of stub dieback indicated that spore release occurred at regular time intervals during each 24-hour period and apparently was associated with the environment. Perithecia are also commonly formed on undecomcomposed stubble in any corn field and air-borne ascospores can be found in the air above minimum tillage corn fields. It has been shown that ascospore isolates gathered from corn stalks were uniformly virulent on carnation stubs. Apparently the air borne stage of this fungus is not only capable of ejecting its spores a sufficient distance to be carried in wind currents but also capable of initiating stub dieback in carnations. The divergence of habit indicates that certain critical environmental factors regulate the airborne stage of this pathogen and that this stage may play an important role in the development of this disease on carnations.

Keywords: Ascospores Fusarium stem rot G. zeae Effect of Temperatures Effect of Light Effect of Relative Humidity

Libraries: Floriculture

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