Today's column in the Chronicle was about black aphids and fava beans. They did print the image I sent, though this one is a little clearer than the one in the paper, which had registration problems. That is, one of the colors in the four color separation is not quite lined up with the other ones. The Chronicle promises a new printing press soon, which will improve the quality of their photo reproduction.
In Britain, this is what they call black fly, though it is an aphid rather than a fly. As I mentioned in the column, they just nip of the tops of the plants, which the aphid are happiest eating, and let the lower flowers form pods. You may prefer to spray with a hard spray of water a few times, or, for a better clean up, use an insecticidal summer oil spray. One spraying might be enough to do it.
People used to use soap sprays to kill aphids, and they may work, but the oil sprays are proving more effective. A good reason to stay with the less-toxic methods, such as the above, is that beneficial insects really will help you get rid of garden pests if you don't use pesticides that kill them.
For example, here is a lady beetle feeding on the black aphids on the same fava bean plant.I only got one shot of it, after which it dove behind a flower and never came out, but it was working away on the aphids. This one is an adult, but the little charcoal gray and orange alligator-like lady beetle larvae eat aphids even faster than the red-orange beetles with black dots that we all recognize.
Hope you can see the beetle. It is just past half way down in this photo, on the stem of the plant, among the flowers.
May your fava beans not get black aphids, or, if they do, may the lady beetles show up!