The last two years I have seen feeding on the dry beans in my organic production systems study at several sites around Michigan. Last year one site was completely defoliated by the pest by R5 (first full length pod), which resulted in significant yield reductions. This year I have been keeping an eye out for these pests and started to see the larvae at my Alma and Columbiaville sites near the end of July. Populations were not high enough to warrant spraying an organic insecticide and fortunately there were still many healthy leaves left for the rest of the season.
For more information on Mexican bean beetle, please visit:
Here are a few pictures I took of the pest and damage in my plots this year: