Short‐term efficacy and nontarget effects of aerial glyphosate applications for controlling Lonicera maackii (Amur honeysuckle) in oak‐hickory forests of Eastern Missouri, U.S.A.

Abstract

Lonicera maackii (Amur honeysuckle) is a non‐native species that has invaded forest stands throughout the eastern United States. This research examined using aerially applied glyphosate in autumn 2013 to control L. maackii in oak‐hickory forest stands in Missouri, U.S.A. We targeted the spraying time period when L. maackii was still green and most native plants were dormant. Across treatment units, the mean difference in L. maackii stem density significantly declined (p = 0.004) by 5.4 stems per plot from spring 2013 to summer 2014 when compared to control units which increased by 1.8 stems per plot. Treated units with a high initial infestation level of L. maackii (>50% cover) had a significant (p = 0.004) decline in the mean difference in L. maackii cover of −50.0% per plot between spring 2013 and summer 2014 compared to an average increase of 9.2% in the controls. Similar results were found for treated units with a low initial infestation level of L. maackii (10–50% cover). Mortality of native overstory and understory trees post‐treatment was negligible. In the ground layer of forest stands with a low initial L. maackii infestation level, native non‐spray‐sensitive forb cover per plot significantly increased (p = 0.023) relative to controls between summer 2013 and summer 2014 while native spray‐sensitive species cover significantly decreased (p = 0.021) during the same period. These results suggest that an aerial application of glyphosate can provide an L. maackii control option, but with trade‐offs in compositional shifts in the native ground‐layer vegetation.

Recovery of herb‐layer vegetation and soil properties after pile burning in a Midwestern oak woodland

“…However, changes in disturbance regimes combined with historical land‐use practices over the past century, including logging and livestock grazing, have led to increased density of mesophytic or fire‐sensitive tree species (Beilmann & Brenner 1951; Guyette et al 2002; Hanberry et al 2014). In unmanaged woodlands and forests near urban areas, exotic shrubs increasingly dominate the understory, contributing to further degradation (Leahy et al 2018).…”

“…Our study site is representative of many fragmented and degraded oak woodlands where pile burning is commonly practiced. First, multiple exotic woody invaders dominated the understory before restoration (Leahy et al 2018), and widespread infestations in the surrounding landscape increase the likelihood of reinvasion after pile burning. Moreover, some exotic woody plants (species of Euonymus, Ligustrum , and Lonicera ) can increase soil nitrogen (N) levels (Mitchell et al 2011; Kolbe et al 2017; Rounsaville et al 2019), which may contribute to their reestablishment and dominance, or promote secondary invasions of undesirable species.…”

Herbicide control of the invasive Amur honeysuckle (Lonicera maackii) does not alter soil microbial communities or activity

“…Mechanical removal alone is largely ineffective because of resprouts from remaining roots and stems (McDonnell et al., 2005), but numerous herbicide control options exist for Amur honeysuckle. These include stump cutting followed by herbicide painting (often glyphosate) (Cipollini et al., 2009; Frank, Nakatsu, et al., 2018; Frank, Saunders, et al., 2018), foliar herbicide spraying of glyphosate (Leahy et al., 2018) and basal bark application using triclopyr formulations (Baker, 2019; Kleiman et al., 2018), among others. Given that glyphosate works best as a foliar agent, and the potential for off target effects from foliar spraying is high (Leahy et al., 2018), it has been recommended that basal bark spraying using triclopyr formulations provides the highest mortality whilst being highly targeted (Kleiman et al., 2018).…”