Stripes and spots: Evaluating an aggregation pheromone, vittatalactone, for western striped (Acalymma trivittatum) and western spotted (Diabrotica undecimpunctata undecimpunctata) cucumber beetles

The western striped cucumber beetle, Acalymma trivittatum, and western spotted cucumber beetle, Diabrotica undecimpunctata undecimpunctata, are key pests of fresh market melons in northern CA. While both species are of concern the most detrimental species is the western striped cucumber beetle due to its affinity for smooth melon varieties such as honeydews and cantaloupes. The adults and the larvae feed on the fruit rind, creating scars and rendering the fruit unmarketable. Current management is mostly limited to intensive foliar applications of broad-spectrum insecticides. Although growers scout the fields, they do not possess effective monitoring strategies. Fortunately, an aggregation pheromone has been identified (vittatalactone) and synthesized for an eastern species, the striped cucumber beetle (Acalymma vittatum). In this study, we examined and evaluated the attractiveness of vittatalactone to western cucumber beetles for two consecutive years (2020-2021). This field experiment was replicated across two organic sites in the Sacramento Valley, CA. Both trials consisted of deploying clear sticky traps that were either baited with vittatalactone or unbaited. In addition, we tested the effect of a commercial floral lure combined with the aggregation pheromone (2020) and the floral lure alone in a factorial design in 2021. We found that beetle captures are highly dependent on the growth stage of the crop (i.e., seedling, vegetative, or fruit). The highest captures appeared to be at the end of the season when the crop was harvested. These findings contribute to the future of vittatalactone as a useful monitoring tool and as an attract-and-kill approach.