Some pest is biting off the flowers on my runner bean plants. I have a total of two beans on twelve plants. All are in bloom but no beans are growing. All that is left is little stalks which should have a bean at the end. I have had this every year but this year is very bad. I noticed a lot of flea beetles on the flowers and wondered if it was those so I sprayed with a bug killer a couple of weeks ago. Still no beans though.