- Tags:
- Forestry,
- Working Forests,
- Climate
It’s summer — why are our white pines turning brown?! This June we’re seeing a dramatic “browning” of white pine needles across the region, and many people have been asking what could be creating this change. We’re happy you're taking notice and are concerned about forest health. So, what is going on?
This is white pine needle cast, or needle blight, a dieback in needles caused by fungal pathogens. Scientists have determined that the persistence of the pathogens is correlated with a wet May-July in the previous year, and if you might recall, last summer was the wettest summer on record! So, it’s not surprising that we're seeing this fungus impacting our white pines in 2024.
Does the blight hurt the trees? White pine needles have a 3-year cycle, and shed their third and sometimes second year needles normally in the fall. So, this needle blight is simply causing the previous year’s needles to brown and fall off early. This pathogen does not impact the first-year needles, which will remain on the tree and continue to grow over the summer, though the tree crowns may look a little sparse until they fully grow in.
Trees are resilient and can recover from episodic outbreaks of these diseases. However, if the trees are already stressed, or experiencing the effects of the needle blight often, their health can be impacted.
Climate change and resulting severe weather changes can also worsen the effects of pine diseases by causing stress on the trees. For example, if this damage is followed by a severe drought, the trees may go into dormancy, impacting their growth and resilience.
In forest settings, one way to reduce the impacts of needle blight and other pine diseases is to thin densely growing pine stands to allow more air flow through the forest. Overcrowding allows fungal spores to easily spread amongst trees, particularly from splashing in rain events. By thinning these pine stands we create space for them to dry faster and reduce splashing. This also reduces competition for resources (light and nutrients) amongst individual trees. Well-managed forests are healthy forests!