They are not picky eaters at all--they will of course eat cucumbers, as their name suggests, but also squash and melons and even hawthorn leaves. I'm very protective of my Zephyr squash that's just starting to come in, so I've been vigilant about the beetles.
More than vigilant. More like a beetlecidal maniac. I prowl the rows, capturing and crushing. There are very few now, but I don't want them to make it to the point in their 6- to 9- week life cycle where they make more beetles. Only two showed themselves today, and both met quick deaths by squishing.
There seems to be some interesting research on drenching the soil with rhizobacteria, which simultaneously promotes plant growth and decreases the production of the phytochemical that encourages the beetles to feed. There are no innoculant blends yet, but it seems like such a great idea--stacking functions--to add beneficial bacteria to the soil and discourage beetles at the same time. There aren't any organic pesticides that are specific to the D.S.C.B. -- just broad spectrum pesticides that would kill beneficials too.
So for now it is prowl and squish. Wish me luck.