Disease Update : Septorioides Needle Blight
By Nicholas J . Brazee , UMass Extension Plant Pathologist
Septorioides needle blight has been an important disease of two- , three- , and five-needle pines in New England for over a decade . The disease is caused by the fungal pathogen Septorioides strobi , which was formally described only recently ( Wyka and Broders 2016 ). Eastern white pine ( Pinus strobus ) is the primary host in southern New England . However , based on samples submitted to the UMass Plant Diagnostic Laboratory , additional hosts include Swiss stone pine ( P . cembra ), limber pine ( P . flexilis ), mugo pine ( P . mugo ), Austrian pine ( P . nigra ), ponderosa pine ( P . ponderosa ), red pine ( P . resinosa ), pitch pine ( P . rigida ), Scots pine ( P . sylvestris ), Japanese black pine ( P . thunbergii ), and red spruce ( Picea rubens ). Additional members of the Pinaceae may serve as hosts but infections are presumably uncommon . Symptoms and signs of the disease can be seen at https :// ag . umass . edu / landscape / fact-sheets / septorioides-needle-blight
Septorioides is one of the primary pathogens responsible for white pine needle damage ( WPND ) in New England ( Broders et al . 2015 , Wyka et al . 2018 ). First documented in 2009 , WPND is a chronic stress for eastern white pines throughout eastern North America . Symptoms of infection by Septorioides may first appear as a tip blight where the base of the needle remains green . Over time , entire needles become yellow-brown to brown and are prematurely shed from the canopy . Additionally , S . strobi is the most common needle blight pathogen found on P . strobus samples submitted to the UMass Plant Diagnostic Laboratory . become conspicuous until the following spring , nearly one year after infection .
Active management for any needle blight pathogen of conifers should focus on protecting the current year ' s foliage from becoming infected in the late spring and early summer . Pruning of heavily diseased branches , especially those in the lower canopy , and removal ( or covering ) of discarded needles can help to reduce disease pressure . Forest studies have shown a direct correlation between thinning density and needle blight severity . When diseased pines are provided more space , light and airflow , needle blight severity decreases .
Many other soft ( five-needle ) and hard ( two- and three-needle ) pines frequently used as ornamentals can also serve as hosts ( see host list above ). In southern New England , infected trees appear scattered on the landscape and encompass all age classes . Like many needle blight fungi , S . strobi produces large volumes of spores that are blown and splashed to nearby branches and trees during wet weather . Climate studies have shown the northeastern U . S . experienced an increase in the frequency and amount of precipitation during the months of May , June and July , which is helping to fuel outbreaks of WPND ( Wyka et al . 2017 ). The May – July period is when WPND pathogens , such as S . strobi , are most actively sporulating and older , diseased needles are shedding from the canopy . This coincides with the period of active needle and shoot development for many pines in the region . These immature needles are susceptible to infection during periods of wet weather or high humidity . Once infected , symptoms may take many months to develop and typically do not
MAA NEWS FALL 2023 16