• The general absence of knees in swamp soils superficially dry during most of the year
• The presence of these protuberances where surface water is excessive for long periods
• The rise of knees to the approximate height of the average flood-stage level
• The interwoven network of, and the anchorage afforded by, a deep root mass beneath the knees
• Fewer knees for pondcypress than baldcypress The Tree's Pests
Baldcypress and pondcypress are notably free of insect problems. The most serious pest is a leaf-chewing beetle, Systena marginalis, which discolors foliage in midsummer. Damage is done by small, flattened, dull yellowish-tan adults. Insects leave trees within three days. They do not consume the foliage, but the leaves turn red within a few days of the attack. Heavy feeding is evidenced by linear-shaped gouging that seldom pierces both leaf surfaces. After foliage turns red, leaves shrink so much that feeding holes are difficult to see unless leaves are soaked overnight in water. Defoliation reduces growth and vigor, enabling secondary pests to further weaken and kill trees.
Cypress stands are also relatively free of rots and other fungi infections. Pecky cypress results from infection by Fomes geotropus—the scientific species name derived from the downward curvature of the dried fungal bracts. These fruiting organs are rarely found on infected trees. Spores of the fungus probably enter through basal fire wounds. Damage, characterized by cavities that eventually occur throughout the heartwood of a tree, is especially serious on overmature stems. These pockets of a pecky nature, generally several inches long, fill with brown powder that might be antiseptic and, thereby, arrest further disease activity. Decades could be required for old trees to die; growth of this Fomes fungus ceases when they do.25
Swamp rabbits are a nuisance in young baldcypress forests. They clip seedlings just above the ground, making a smooth-angle cut. Clipped stems generally resprout, but inundation kills short shoots. Beavers, too, destroy seedlings as they forage, especially if the young trees are nursery-grown and, thus, nutritionally rich.
Nutria, the aquatic rodent introduced from South America in the 1930s to control lake vegetation (and possibly for its pelts), uproot seedlings, eat bark from tap roots, and, in some cases, consume whole roots. Damage occurs in the spring, on flooded sites first and then on adjacent non-flooded areas, for a distance of 15 to 20 feet from the water's edge. Easily distinguished from swamp-rabbit injury, the cut is rough and at an angle of about 40 degrees. As seedlings are carried back to the water to be eaten, the nutria leave sections of debarked roots and seedling tops strewn upon the surface of the pond. Ninety percent survival of 3-month-old seedlings occurs where nutria are absent; in the presence of the rodent, total destruction results.26
Baldcypress trees are intolerant of salt intrusions, which sometimes occur with flooding. These trees are also known for the aesthetically pleasing Spanish moss that drapes from their branches. In this fibrous material, the yellow-throated warbler forages.
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