Red maple (Acer rubrum) is one of the most widely planted ornamental trees in the United States. In nursery production systems, weeds are routinely managed with herbicide applications, which can result in accidental overspray to tree trunks. This chemical exposure may compromise plant defenses and increase vulnerability to insect pests such as Chrysobothris spp. (Buprestidae). We investigated how herbicide exposure alters the phytochemical profiles of two maple cultivars— ‘Autumn Blaze’ and ‘Brandywine’ —possibly altering oviposition behavior. Trees were treated with Scythe® (pelargonic acid), Roundup® (glyphosate), or left untreated (control). Foliar and bark phytochemistry, including polyphenols, tannins, sugars, starches, and foliar VOCs monitored over four weeks. Late-season assessment of oviposition attempts and larval presence showed that ‘Brandywine’ trees received more oviposition attempts than ‘Autumn Blaze’ across all treatments. Notably, only one oviposition attempt occurred on an ‘Autumn Blaze’ individual, under the Roundup® treatment. Within ‘Brandywine’, Scythe®-treated trees, phytochemical analyses revealed cultivar-specific differences in response to herbicide stress. ‘Autumn Blaze’ exhibited a consistent decline in foliar and bark polyphenol concentrations over time. In ‘Brandywine’, Scythe® caused reductions in bark tannins and sugars over time, suggesting a compromised defense profile in this treatment group. Additionally, in Scythe®-treated ‘Brandywine’ cultivars, polyphenols increased in bark tissues, possibly acting as oviposition stimulants. These findings indicate that herbicide-induced phytochemical changes are cultivar-dependent and may influence host selection behavior by Chrysobothris spp. Understanding these interactions is critical for integrated pest management in ornamental nurseries, especially in the context of cultivar selection and herbicide application strategies.
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