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Amur honeysuckle (Lonicera maackii) is an important invasive plant species in the Ohio River Valley. Previous work has shown extensive dieback of honeysuckle in the region, coupled with the appearance of the native fungal pathogen, honeysuckle leaf blight (Insolibasidium deformans). Our goal was to find if the blight causes growth decline or mortality in Amur honeysuckle. Seedlings were grown under greenhouse conditions in 2017. Treated seedlings were sprayed with a spore solution prepared from blighted leaves that were collected from the field. They were placed into a growth chamber with conditions set for optimum spore growth and then returned to the greenhouse after leaf blight began to develop. Growth (height, total stem length, leaf area, and leaf number) and dark-adapted chlorophyll fluorescence (Fv/Fm) were measured periodically over the growing season. A repeated-measures analysis of aboveground growth indicated that larger, faster-growing plants were more likely to be infected, but their growth rates were subsequently reduced much more than uninfected treated plants and controls. There were positive correlations between Fv/Fm and RGR (relative growth rate). Blighted leaves had lower values of Fv/Fm than uninfected leaves. No infected plants died, but this experiment supports our hypothesis that leaf blight causes a significant growth decline in Amur honeysuckle. Future work will determine if the patterns seen under greenhouse conditions hold in the field.

Amur honeysuckle (Lonicera maackii) is an important invasive plant species in the Ohio River Valley. Previous work has shown extensive dieback of honeysuckle in the region, coupled with the appearance of the native fungal pathogen, honeysuckle leaf blight (Insolibasidium deformans). Our goal was to find if the blight causes growth decline or mortality in Amur honeysuckle. Seedlings were grown under greenhouse conditions in 2017. Treated seedlings were sprayed with a spore solution prepared from blighted leaves that were collected from the field. They were placed into a growth chamber with conditions set for optimum spore growth and then returned to the greenhouse after leaf blight began to develop. Growth (height, total stem length, leaf area, and leaf number) and dark-adapted chlorophyll fluorescence (F v/F m) were measured periodically over the growing season. A repeated-measures analysis of aboveground growth indicated that larger, faster-growing plants were more likely to be infected, but their growth rates were subsequently reduced much more than uninfected treated plants and controls. There were positive correlations between F v/F m and RGR (relative growth rate). Blighted leaves had lower values of F v/F m than uninfected leaves. No infected plants died, but this experiment supports our hypothesis that leaf blight causes a significant growth decline in Amur honeysuckle. Future work will determine if the patterns seen under greenhouse conditions hold in the field.

Amur honeysuckle (Lonicera maackii (Rupr.) Herder) is recognized as one of the most important invasive species in the Ohio River Valley. Since 2012, outbreaks of the native pathogen honeysuckle leaf blight in the region have been observed, coincident with the report of high levels of L. maackii dieback in an open-grown stand in northern Kentucky. The purpose of this study was to quantify the extent of dieback in the area and to determine whether dieback was also present in stands growing under forest canopies (forest-understory). Data were collected from plots placed along transects for eight open-grown and six forest-understory sites in northern Kentucky and nearby southwestern Ohio in 2014–2016; diameters at stump height (25 cm) of all live and dead woody stems were measured in the plots. For L. maackii in open-grown stands, 30% and 23% of stem density and basal area, respectively, were dead, which was higher than that seen for associated shrubs and small trees; it was also higher than that reported in the 1980s for L. maackii in open-grown stands in the region. Mortality in the larger-size classes was higher than that seen in the 1980s. By contrast, stem mortality of L. maackii in forest-understory stands varied little from that seen in the 1980s. Basal area mortality was similar to associated species. The possible role of leaf blight in the decline of open-grown L. maackii requires further investigation.

Amur honeysuckle (Lonicera maackii (Rupr.) Herder) is recognized as one of the most important invasive species in the Ohio River Valley. Since 2012, outbreaks of the native pathogen honeysuckle leaf blight in the region have been observed, coincident with the report of high levels of L. maackii dieback in an open-grown stand in northern Kentucky. The purpose of this study was to quantify the extent of dieback in the area and to determine whether dieback was also present in stands growing under forest canopies (forest-understory). Data were collected from plots placed along transects for eight open-grown and six forest-understory sites in northern Kentucky and nearby southwestern Ohio in 2014–2016; diameters at stump height (25 cm) of all live and dead woody stems were measured in the plots. For L. maackii in open-grown stands, 30% and 23% of stem density and basal area, respectively, were dead, which was higher than that seen for associated shrubs and small trees; it was also higher than that reported in the 1980s for L. maackii in open-grown stands in the region. Mortality in the larger-size classes was higher than that seen in the 1980s. By contrast, stem mortality of L. maackii in forest-understory stands varied little from that seen in the 1980s. Basal area mortality was similar to associated species. The possible role of leaf blight in the decline of open-grown L. maackii requires further investigation.

Amur honeysuckle (Lonicera maackii) is recognized as one of the most important invasive species in the Ohio River Valley. In 2012–2013, an outbreak of honeysuckle leaf blight on this species was observed in the region around Cincinnati, OH, USA. Dieback of open-grown honeysuckle stands was then noted in 2013, along with reduced physiological performance. One of these stands with signs of blight and dieback was surveyed in late summer 2013. The honeysuckle dead/total stem density fraction was 61.8 %, compared to 3.2 % reported in the 1980s. The dead/total basal area fraction was 36.9 %. The stem population size structure may also indicate a decline. Future work is needed to determine how widespread the decline is and if the leaf blight is the causative agent or an opportunistic infection.