White Pines Impacted by Needle Diseases and Changing Climate
Posted: July 27, 2016
Needles on both mature and young trees have turned yellow to brown, causing premature shedding and sparse canopies. Severely affected trees can quickly decline further and die.
So what is happening to eastern white pines? Although it is not entirely understood, recent studies have led plant pathologists to believe it is caused by a combination of four needle blight fungi, changing climatic conditions and other stressors that are causing problems for white pines in the region.
The four needle fungi that have been identified on white pine are
- Lecanosticta acicula (formerly Mycosphaerella dearnessii)
- Lophophacidium dookssi (formerly Canavirgella banfieldii)
- Bifusella linearis
- Septoriodies strobi.
But these needle diseases (fungi) need the right environmental conditions to all of a sudden become a problem for white pines. The changing climate in the northeast has been positively correlated with damage from needle diseases.
During the spring of 2015, May was extremely dry with above-average temperatures, while June saw above-average rainfall. Those heavy rains promoted fungal sporulation and dispersal of needle diseases just as new needle growth was emerging on the white pine trees. The rains in June were followed by above average temperatures from July through December, causing some heat and drought stress for pines that lost much of their new growth. These temperatures may have impacted pines acclimation for winter hardiness, leading to some injury in January and February 2016. During May and June of 2016, we have seen relatively dry conditions, which will be good for the next crop of needles. If we have normal rainfall through July, the incidence of needle blight should be a lot less.
As our climate continues to change and new insect and disease species are imported and discovered, our landscapes will continue to change over time. Hopefully healthy eastern white pines will recover and adapt, but repeated defoliation caused by these needle fungi will certainly cause mortality in our forests and landscapes.