White pine blister rust (WPBR) is caused by the fungus Cronartium ribicola. The disease was introduced into the United States from Europe in the early 1900s and spread quickly, causing significant white pine mortality. Because currants and gooseberries (Ribes sp.) are also a host for the disease, infection of white pine increases when they are planted nearby.
Certain species of currants and gooseberries were once considered resistant to transmitting the disease. Until recently, gardeners could plant these specific varieties with a permit. However, a survey in 2012 and 2013 on Ribes plants in New Hampshire confirmed WPBR on resistant varieties. In response to this re-emerging forest health threat, the N.H. Division of Forests and Lands changed the allowed list of approved currants and gooseberries.
USDA Forest Service Publication, How to Identify White Pine Blister Rust and Remove Cankers
White Pine Blister Rust -- Infection Incidence for Selected Areas of NH (Lombard, Bofinger, 1999)