Cryptocline Needle Blight of Yew ( Taxus spp .)
By Nicholas J . Brazee , UMass Extension Plant Pathologist
Cryptocline needle blight , caused by the fungal pathogen Cryptocline taxicola , can be a serious disease of ornamental yews in the managed landscape . Based on samples submitted to the UMass Plant Diagnostic Laboratory , English yew ( Taxus baccata ), Japanese yew ( T . cuspidata ), and hybrid yew ( T . × media ) are all susceptible to infection . The pathogen has also been found on Pacific yew ( T . brevifolia ) and Canada yew ( T . canadensis ).
Because yews have so few associated diseases , the damage Cryptocline is able to cause can be quite dramatic at times . Cryptocline often attacks the current season ' s shoots and needles before they mature and harden off . Foliar symptoms can develop as scattered , pale green to brown-colored lesions that expand over time to consume the entire needle . When the shoots die , the needles are typically held in place and become pale brown . Signs of the pathogen are often absent in the field but after brief periods of incubation in moist chambers , dark and rounded fruiting bodies ( acervuli ) emerge from both the upper ( adaxial ) and lower ( abaxial ) surfaces of infected needles . They may develop tufts of gray-colored mycelia that appears similar to Phyllosticta and Botryosphaeria . Discharged spores are splashed or blown onto nearby shoots and needles to initiate new infections . Little is known about the life cycle , but infections most likely develop in the spring and early summer during mild and wet conditions . It ' s also possible that the fungus can invade tissues in the fall if environmental conditions are ideal . Shade favors the development of most fungal pathogens , as they require moisture on plant surfaces for spores to germinate and infect . from infected plants . If possible , remove or cover the dead , discarded needles at the base of the plant with mulch since they also harbor the pathogen . If left at the site , the fungus will readily overwinter , allowing C . taxicola to sporulate the following spring and potentially infect next year ' s new growth , perpetuating the disease cycle . Research and trials are lacking for this pathogen and host but broad-spectrum fungicides such as copper-based products and mancozeb should have some utility against the pathogen . Applications should be made in the spring when new growth is half-elongated and regular intervals thereafter if wet conditions persist . Increasing air-flow and sunlight is also recommended to reduce the time that free moisture lingers on shoots and needles .
Photos of Cryptocline needle blight symptoms and signs can be found in this UMass Extension fact sheet at https :// ag . umass . edu / landscape / fact-sheets / cryptocline-needle-blight .
Overall , Cryptocline needle blight does not appear to be a common disease of yews across our managed landscapes . Plants under stress from wet / heavy soils , transplant shock , drought , among other stresses , are more likely to develop significant disease outbreaks . Prune out and discard all blighted shoots
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