Examining abiotic drivers of variation in biocontrol efficacy of invasive plants across environmental gradients

Classical biological control is widely accepted as an efficient strategy to manage invasive plants. However, the effectiveness of biocontrol agents can be highly variable, where even an efficient agent may be ineffective under certain environmental contexts. For example, a favorable environment for plants may allow for greater defense allocation, helping plants to thwart biocontrol attacks. Air potato (Dioscorea bulbifera) is a problematic invasive weed that inhabits Florida and a beetle Lilioceris cheni (Coleoptera) has been successfully established as a biocontrol agent. However, damage levels to the vine and establishment of beetle have been highly variable across the state resulting in varying levels of vine management. Rapid evolution of the plant is unlikely as it reproduces asexually. Therefore, climatic variation across Florida may be a primary driver of variation in beetle efficacy by mediating plant defense production. We tested how variation in the environment influences plant growth and defense traits through various field and lab-based chemical and feeding assays, using natural populations of air potato across Florida. Plant populations across Florida were highly variable in vigor and defense traits. Additionally, we tested whether the exogenous application of salicylic acid (SA) and jasmonic acid (JA) can alter biocontrol efficacy of L. Cheni. We hypothesized that JA would decrease and SA will increase the beetle foraging. However, JA treatment significantly increased the beetle foraging than SA treatment.  These results provide a foundational understanding of the factors that cause variation in efficacy of biocontrol agents and will help in improving future biocontrol programs.