Cabbage aphid biocontrol in broccoli by syrphid fly larvae

In the Mother Trial at CASFS-UCSC, the effects of fertility and predation (via syrphid larvae) were analyzed with respect to cabbage aphid abundance and broccoli harvest. Half of all broccoli plants (across all fertility treatments) were sprayed with Entrust, an OMRI-approved insecticide designed to suppress syrphid larvae (Fig. 1). This predator suppression allowed us to quantify the benefits of predation and properly correlate unadulterated fertility and aphid pressure. In plots where Entrust was applied, aphid abundance increased and harvest rates decreased (Fig. 2). Unfortunately, tri-trophic fertility effects (i.e. fertility x broccoli x aphids) were not consistent across treatments, such that aphid densities, either in syrphid-suppressed or control plots, did not vary as predicted (Fig. 3). A grower-friendly syrphid larvae extension guide is being assembled that will allow users to identify the most common pest (i.e. caterpillar) and beneficial larvae found on cole crops. Once completed copies will be accessible via this website