On Mar 2, 2007, Raine_Bradford from Paonia, CO wrote:
These nasty little monsters can devastate your bean crop if not kept in check. I try to control them by just squishing all the little yellow eggs that appear on the undersides of the leaves every time I pick the beans. Rotenone also works fairly well for the organically conscious, but you have to be sure to spray the undersides of the leaves. Once the eggs hatch, the nymphs and adults will feed on the beans themselves, causing ugly, misshapen beans.
On Mar 9, 2007, IAJo from Peosta, IA (Zone 4b) wrote:
These bugs ruin your green beans with little bites that turn into black spots all over them, and they bite hard when they land on exposed skin. They also seem to infiltrate homes and like to be in sunny areas and crawl on the ceilings. The best remedy in the house to vacuum them up. NEVER squash them inside, they have a horrible bitter odor. The birds will not eat them, so they probably are a nasty tasting b ug. I use a spray or powdered insecticide on my beans approximately 5 to 7 days before I want to harvest them, so the insecticide is usually washed off by rain or the sprinkler.
Mexican bean beetles decimated our beans in 2005. I used a pyrethrum (chrysanthemum-based) pesticide, but apparently applied it too late or lightly. The pyrethrum was suggested by an uncertified organic grower, but some pyrethrum products may now be certified for organic use.
In 2006, I used lightly anchored floating row-covers to keep the beetles off of the plants, that kept the numbers manageable with very minimal spraying and hand-picking
As the others have noted, these bugs - in both beetle and caterpillar form - turn bean leaves into lace and eat and deform beans as well. I have tried several neem formulations without much success - hand-picking/squishing the bugs seems most effective.
Question: if you use a row cover, how do the flowers get pollinated?