These are aphids, a very common plant pest that usually doesn't require much intervention, though they are capable of reproducing quickly. They are easy to squish, or if you prefer, they can be blasted off of the foliage with a strong spray of plain water from a hose. (A handheld mist bottle probably won't have enough water pressure.) The small white rice-shaped object in the photo might be the egg of a beneficial insect that will prey on the aphids once it hatches. Fortunately, there are many such beneficial insects that consume aphids, and they tend to arrive sooner or later after an aphid population develops, so intervention usually doesn't have to continue for long, and avoiding insecticide use can help preserve these helpers so they suppress the aphids naturally.

Miri