Bagrada bug pressure on desert cole crops appears to finally be letting up. Based on our trials here at YAC and reports from numerous PCAs in Coachella, Imperial, Blythe and Yuma, the adult numbers on new stands have been much lower in the past week. On older stands, the plants now appear to be growing "normally" and insecticide applications are providing longer residual (go to this link for early results of an efficacy trial). In other research trials, it appears that soil applied neonicotinoids are proving some relief against adults as well. Broccoli plants and cauliflower transplants that were treated with soil applications of imidacloprid (Admire, Alias, Nuprid, etc) or clothianidin (Belay) at planting are significantly larger than untreated plants at 30 days after wet date. Although treated plants (at cotyledon or transplant stages) took some damage at stand establishment, it seems that once the plants produced fully expanded leaves the soil insecticides began to provide protection from Bagrada bugs. However, the ultimate impact of the Bagrada bug infestations may not be evident until harvest when we can assess maturity and quality of the crops that were heavily attacked early in stand establishment.

Although bug numbers have declined, PCAs should still remain vigilant and scout fields thoroughly for the presence of adults, and signs of new feeding damage (tattoo like feeding scars) on cotyledons and young terminal leaves. Research here at YAC on Bagrada adult activity has suggested that adults appear to be most active and abundant on plants in fields during the warmer parts of the day (9:00 AM to 4:00 PM), and least abundant on the plants early in the morning (4:00 AM to 8:00 AM) (see this link for preliminary findings). Thus, the highest probability of finding Bagrada bug adults on plants would be during mid-day. This may also be the best time to apply insecticides as well.

To contact John Palumbo go to: jpalumbo@ag.arizona.edu

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.