'The black blister beetle, also known as the Yankee bug and just plain 'blister beetle'. . . is a fairly long (up to 3/4") and slender beetle, with soft, flexible wing covers. The entire body is black or dark gray, and the covers may be marked with white stripes or margins. Another species, the margined blister beetle, is distinguished by a narrow gray or yellow margin on the covers. Blister beetles are very active, and frequently appear in large numbers in the latter part of June and through July.
'Handpicking is effective in controlling this pest, but you should protect your hands with gloves, as the beetles discharge a caustic fluid that is harmful to the skin. Some growers achieve control by dusting with equal parts lime and flour. This should be done at the warmest time of the day.
'Blister beetles are usually found in swarms or colonies feeding on the blossoms and foliage of any of a number of garden and field crops--vegetables, vines, trees, and flowers."
We have both species mentioned here--the black/grey and the lighter striped ones. Last year both were out in force, and it was terrible. What they don't completely devour, they ruin with their icky black droppings. I didn't know about that lime/flour solution until reading it just now. It sounds interesting. I would start with that as it is totally safe. Look for lime at a feed/farm supply store or nursery or garden center--it's very inexpensive.
Last year I ordered some Liquid Rotenone-Pyrethrins Concentrated Spray from Gardens Alive. They are a great company that sells all kinds of natural fertilizers, insecticides, etc. They also have a mail order catalog available. Rotenone is natural, but it is pretty strong stuff--usually a last resort option for organic growers. You might also check their catalog or website for other products that kill blister beetles.
I bought it after the blister beetle invasion, and fortunately this year they haven't been nearly as bad, so I haven't actually tried it yet. It's also good for all kinds of other pests, too.
I have read various other 'folk tale' remedies--like that they won't cross wide, empty spaces so you should either leave wide rows between plantings or once they have invaded, clear out the surrounding weeds, grass, plants, etc. I've even read about people yelling at them to scare them away. Who knows. When I'm desperate, I'll try some pretty crazy sounding things myself!
I've never gone the hand-picking route, as there were always way too many of them--hundreds and hundreds last year. They also run fast! But that would be your best bet if you only have a few to contend with. I hope this helps. Good luck!"
She came back and said:
"Thank you kindly for the information! Those terrors seem to be gone for now, but we'll know what to do next time. We thought we had gotten rid of them once, but they showed up a second time. It's good to know some natural remedies to try. Much appreciated!"
taken from inmykitchengarden.blogspot.com