A mysterious blight of white pine, first diagnosed in 1908 and called emergence tipburn, may be due to excessive ozone in the atmosphere, by sulfur dioxide given off where coal is burned, or by chlorine released from stacks in the effluent of manufacturing processes. Terminal halves of the current-year's needles turn brown and die, usually in midsummer. The dead needle ends then break off. Chlorosis of dwarfed needles and stunted shoots, accompanied by shriveled or wrinkled bark, occur for several years thereafter. Resistance may be genetically inherited.
Chronic air pollution stress may also cause declining vigor of sensitive eastern white pines in the Southern Appalachian Mountains. Needle length and needle persistence diminish with lowered rate of respiration and changing carbohydrate translocation patterns.5
Of the insects, white pine weevils are the most destructive to this species in the Southern Appalachians, though these had not been recorded there prior to the mid-1950s. The sporadic appearance of the low-flying adult is usually attributed to the absence of young stands in groups sufficiently contiguous for continuous breeding of the insect.
Several polypore (Polyporus) fungi, a needle cast fungus, aphid-like chermids, cone beetles, and pales weevils also take their toll in these forests, as they do for many other conifers. Sunscald, while not a biological pest, damages and kills these thin-barked conifers, especially if trees on south- and west-facing exposures are released too drastically from shade-providing competition.
Some mammals and birds contribute to controlling the extent and vigor of white pine woodlands. Gray and red squirrels and white-footed mice consume an abundance of seeds, the former by day, the latter by night. Seeds are "squirreled" in caches containing green cones, the rodents apparently ignoring the disseminated seeds on the ground. Mice, in contrast, devour seeds in place and also carry away squirrel-collected seeds to store. Mice and voles together are capable of consuming nearly all naturally disseminated seeds in the forest. Where they abound, few seeds are left for the mourning doves, which then peck at fallen cones to extract seeds. White-tailed deer can severely graze white pine seedlings in openings, such as logging skid trails in a thinned stand of trees. On the other hand, they do minimal damage to seedlings overtopped by brush.
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