However, heavy shade can be detrimental to white pine growth. There must be a balance between sufficient shade to reduce weevil injury and enough light to maintain adequate tree growth. Most unmanaged stands have a natural crown closure of 70-80 percent. A second important silvicultural practice is to maintain high densities of young white pine until the trees reach about 20 feet in height. This is especially important in open-grown plantations.
Density creates competition, it forces rapid height growth with minimal terminal diameter growth.
In addition, it causes natural lower branch mortality which augments pruning for rust control. Pruning and destruction of the dead terminals at this time not only helps correct the injury but may reduce the local weevil population for the following year. Pruned terminals should be destroyed or removed from the site. This will provide enough shade to discourage weevils and reduce blister rust infection, but allow in enough light for adequate growth. Most unmanaged natural stands have 70-80 percent crown closure.