Black Walnut Allelopathy in a 28-Year-Old Loblolly Pine Stand and Implications for Initial Plantation Establishment

Damaged and dying loblolly pine trees (Pinus taeda L.) were found around black walnut trees in a 28-year-old plantation in Chatham County, NC. The damage and mortality are attributed to disease caused by walnut allelopathy. Damage is first evident by the presence of resin exudation on the lower trunks of affected trees. As damage progresses, resin exudation occurs higher on the trunk, eventually reaching heights of more than 10 ft (3 m). The phloem and sapwood beneath the resin exudation are killed thereafter leading to termite invasion and bird predation. Affected trees eventually die. Sampling of black walnut trees and the affected pines in their vicinity indicated the following: most of the resin exudation (95.6 percent) is found on the side of the pines facing the black walnut tree, pine mortality increases as resin flow height increases, larger diameter black walnut trees result in farther damage extent, and damage extends beyond the dripline of the black walnut tree. Before establishing loblolly pine plantations, the planting area and vicinity should be surveyed for the presence of black walnut trees. It is recommended that no pines be planted within 35 ft (10 m) of driplines of established black walnut trees. If black walnut trees are found in the vicinity of a pine plantation, the plantation should be surveyed at least every 5 years to locate and eliminate any newly established black walnut seedlings.

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Author(s): Coleman A. Doggett, Michael J. Perry, William R. Doggett

Publication: Tree Planters' Notes - Volume 59, Number 1 (2016)

Volume: 59

Number: 1