WPBR cannot spread directly from tree to tree. It requires an alternate host, Ribes spp. (currants and gooseberries) to produce spores that can then infect white pine trees. To prevent the spread of WPBR, several states, including New Hampshire, decided to prohibit the sale or planting of any Ribes species and started aggressive Ribes eradication programs. Ribes plants were uprooted or treated with herbicides in widespread forestry efforts in New Hampshire from 1917 until the late 1970’s.
While WPBR infection is not uncommon in present day New Hampshire, the severity of the incidence of infection has declined dramatically. This drop in WPBR infections is partly attributed to the Ribes eradication programs, which reduced the number of Ribes spp. available as an alternate host for WPBR.
When research and selective breeding produced Ribes plants resistant to WPBR, the state of New Hampshire began to allow limited sales of these resistant varieties via a Ribes permitting program. The selection of desirable varieties was initially fairly limited, but several varieties of currants and gooseberries have been recently added to the list of approved resistant species. The Division and the New Hampshire Department of Resources and Economic Development (DRED) have a policy to regulate the planting of approved Ribes species within the state.
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