Bagrada bug update

By John Palumbo, UA Research Scientist and Extension Specialist

Bagrada bug pressure on desert cole crops appears to finally be letting up. Based on trials at the Yuma Agricultural Center (Yuma, Ariz.) and reports from numerous pest control advisers (PCAs) in Coachella, Imperial, Blythe and Yuma, the adult numbers on new stands were much lower last week.

In older stands, the plants now appear to be growing "normally." Insecticide applications are providing longer residual coverage.

In other research trials, soil applied neonicotinoids are providing some relief against adult Bagrada bugs as well. Broccoli plants and cauliflower transplants 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 the wet date.

Although treated plants at the cotyledon or transplant stages took some damage at stand establishment, it seems that once the plants produced fully expanded leaves that the soil insecticides began to provide protection from Bagrada bugs.

The ultimate impact of the Bagrada bug infestations may not be evident until harvest when we can assess the maturity and quality of the crops that were heavily attacked early in stand establishment.

Although bug numbers have declined, PCAs should  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.

YAC research on Bagrada adult activity suggests that adults appear to be most active and abundant on plants in fields during the warmer parts of the day (9:00 - 4:00), and least abundant on the plants early in the morning (4:00 to 8:00). Click on this link, http://extension.arizona.edu/sites/extension.arizona.edu/files/resourcefile/resource/marcop/Bagrada%20bug%20Activity.pdf, for preliminary findings.

The highest probability of finding Bagrada bug adults on plants is during the midday. This may also be the best time to apply insecticides.

Contact Palumbo: (928) 782-3836 or jpalumbo@ag.arizona.edu.