2018 ASHS Annual Conference

Plants respond to pest attack by triggering several changes in biochemical contents namely primary and secondary metabolites. Phenolic acids are organic compounds that influence pest behavior, feeding efficiency and could limit herbivore damage based on their activity as feeding deterrents. These organic compounds play a role in indirect plant defense by attracting natural enemies and may vary with management systems used for production of organic vegetables. A research project was conducted with a goal to link phytochemicals to striped cucumber beetle (SCB) population and parasitism when organic cucumber plants were grown in rolled-crimped cover crop plots and compared to those in plastic mulch with and without insectary strips. Results showed that SCB populations in 2017 were much lower compared to 2016 and was slightly greater, although not significantly, in plastic compared to rolled mulch. Proportion of SCB parasitism by tachinid fly was slightly greater in plastic than in mulch but did not differ between insectary and no insectary treatments as anticipated. Concentration of rosmarinic acid and syringic acid were significantly greater in leaves of cucumber plants grown in plastic mulch than in rolled mulch. Syringic acid is known to attract parasitoids. However, feurlic and p-coumaric acids were significantly greater in cucumber plants grown in rolled mulch systems. These latter compounds were documented to serve as feed-deterrent for certain pest insects and could explain the lower level of SCB density and parasitism in rolled mulch treatment. There was no direct and measurable effect of presence or absence of insectary strips on SCB density, parasitism, and concentrations of polyphenols in cucumber plants. However, this tactic was found to enhance densities of ground beetle and wolf spiders (other ground natural enemies to SCB). This multi-tactic approach could serve as a potential biocontrol management system for attracting insects and controlling SCB.