White pine blister rust is caused by a fungus which requires multiple hosts to complete its life cycle. All species of white pine are susceptible, they have seemingly low resistance and high mortality rates.
White pine (Pinus strobus) is a critical member of eastern forests, ecologically and economically. There are currently 3 tree diseases threatening the health and sustainability of white pine co-dominant forest systems. The first affliction facing white pines is white pine blister rust (WPBR); introduced in the 1900s this disease continues to seriously threaten forest and agricultural resources. The fungus that causes WPBR requires 2 hosts to complete its life cycle, the alternate hosts are most commonly members of the Ribes genus (gooseberry or currant). Aeciospores colonize the gooseberry plant and produce basidiospores which will infect pine trees when the leaves are shed in the fall.
A quarantine was put in place restricting the cultivation of gooseberry plants in the 1920s by the federal government. The quarantine was lifted by the 1960s but many northeastern states have established their own restrictions for growing these plants, although many states amended their regulations upon the advent of new, disease resistant gooseberry cultivars. However, in 2011 some of these resistant, cultivated gooseberries were found in Connecticut to no longer be immune to WPBR.
The second major issue facing white pines is the seemingly unprecedented epidemic of foliar diseases that have been devastating white pines since the wet spring of 2010. White pines have been repeatedly defoliated by these pathogens. The long-term effects of these foliar diseases or climate conditions which favor their development are largely unknown at this time.
And finally, Caliciopsis canker has become a disease of concern among white pine forest systems. This is a native disease and has been found connected with tree mortality in Georgia, West Virginia, New Hampshire and Virginia. These cankers degrade wood quality and severely reduce plant vigor, but little is known about management and control of this disease.
Caliciopsis canker and fruiting bodies can be seen in this photograph. Unfortunately little is known about controlling this disease.
Agents affecting white pine health or contributing to the decrease in wood quality and value will have far-reaching economic, ecological and even social effects. The U.S. Forest Service, state agencies, state foresters and forest health professionals are working to stem the spread of diseases among white pines, remove factors contributing to disease development and educate the public regarding white pine diseases and what can be done to preserve forest health:
- In 2012, the New Hampshire Division of Forests and Lands did a preliminary survey of WPBR incidences statewide, following a more intensive survey in 2013, they removed all gooseberry cultivars previously thought to be immune from the approved planting and sales lists. The department continues to collaborate with Cornell University and the Canadian Forest Service to develop and implement controls.
- The Northeastern Area Forest Service, in conjunction with state agencies, completed aerial surveys which identified 76,000 acres of foliar damaged white pines in New Hampshire, Massachusetts, Maine and Vermont.
- Scientists and researchers at the University of New Hampshire (UNH) and the Northeastern Area Forest Service have identified several pathogens contributing to the foliar diseases. They continue to search for other possibilities and find effective controls.
- The Northeastern Area Forest Service is collaborating with UNH, the University of Maine (UMaine), and forest health specialists from Maine, Massachusetts, New Hampshire, and Vermont to assess long-term impacts to tree health from foliar pathogens as well as the climate conditions conducive to their development.
- A pest alert educational packet was written, printed and distributed to resource managers in the northeast by the Northeastern Area Forest Service.
If you have concerns regarding the health of white pines or other 5-needled pine species on your property, contact your arborist and visit: http://www.savatree.com/tree-disease-treatment.html.
Crawford, R., Ferguson, T., and Munck, I., U.S. Department of Agriculture; Forest Service/Northeastern Area State and Private Forestry, “White Pine Health; Diseases Threaten White Pines in the Eastern U.S.” January 2014
