Effects of honeysuckle leaf blight (Insolibasidium deformans, Platygloeaceae) on Amur honeysuckle (Lonicera maackii, Caprifoliaceae) stand and stem structure in northern Kentucky

Abstract

Amur honeysuckle (Lonicera maackii) is an invasive shrub with major effects on native ecosystems in eastern North America. Over the past decade, major outbreaks of the native honeysuckle leaf blight (Insolibasidium deformans) have been observed on Amur honeysuckle in the Ohio River valley on an annual basis, and there is evidence of decline in honeysuckle stands in that region. Recent work suggests that the leaf death caused by this fungal pathogen has the largest effect on small shrubs, particularly those growing in the open. This study looked at shrub and stem diameter distributions of seven open-grown and three forest-canopy stands in northern Kentucky and southwestern Ohio. Shrub diameters were fit to the two-factor Weibull function. All stands had reverse-J-shaped diameter distributions, and the Weibull shape parameters indicated that shrub abundance decreased with diameter in all stands. Stand densities and basal areas fell within the range seen in previous studies. However, stem distributions showed a higher proportion of small stems (and in some cases small dead stems) than seen in the 1980s. This unexpected production and death of small stems is consistent with mortality caused by honeysuckle leaf blight, which targets small-diameter long shoots.