Amur honeysuckle (Lonicera maackii) is the most important invasive 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. 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. Treated and control plants were placed separately into a growth chamber with conditions set for optimum spore growth (~100% relative humidity and 16°C) and then returned to the greenhouse after leaf blight began to develop on treated plants. Growth and dark-adapted chlorophyll fluorescence were measured periodically over the growing season.
Results/Conclusions
Treated plants that developed blight had greatly reduced leaf area, chlorophyll fluorescence, and relative growth rates relative to plants that were clear of symptoms. A repeated-measures analysis of aboveground growth indicated that larger, more quickly growing plants were more likely to be infected, but their growth rates were subsequently reduced much more than uninfected plants. 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.