Bean and legume pests and diseases are not a major issue and you are unlikely to see many problems with your crop that are too difficult to deal with.
Blackfly is probably the most common pest, and these aphids can do a lot of damage if they are not dealt with.
If you have an infestation of blackfly on broad beans, it is an easy
fix as the flies tend to attack the growing tip, so simply cut it off.
On other beans it is rarer to get an attack, although sometimes you can
have an infestation of blackfly on climbing French beans. It all depends on the weather, and your climate. These things go in cycles.
Deal with this by spraying with a home-made soap spray, (with a touch of chilli).
bean and legume varieties such as peas can also be eaten by pea and
bean weevils, but this is not a serious problem. This bug eats the
plants leaves and once the plant has reached a certain size they can
usually overcome any damage.
The pea moth can deposit an egg into the flower which will turn into a maggot that eats into the pea. To find out if you have pea moth, drop shelled peas into cold salty water and the maggot will float off.
If you have a particularly bad problem in your area you can buy pea moth pheromone trap that trap the males and stop them from mating with the females, which ultimately stops them from laying eggs.
Chocolate Spot and Rust are fungal diseases that affect broad beans, Chocolate Spot is recognisable by small reddish brown spots on the leaves of the plant, appearing after cool dry periods, usually in late spring, Rust looks like small dusty brown spots often with a yellowish border.
Sometimes these spots can grow and spread, and in the worse cases either cause the collapse of the plant stem, or the plant to loose leaves.
There is no control for these diseases, but they rarely do enough damage to cause much worry. Simply pick beans when young and avoid using the beans as seeds from an affected plant. Proper spacing may help the spread of each fungus, and it is good practice to destroy any affected plants at the end of the season.
Halo blight mainly affects the runner bean and legume varieties such as peas, mangetout and French beans, broad beans are rarely affected. It is identified by leaf spots surrounded by a lighter colored halo, turning reddish brown as the disease develops and finally releasing a white substance.
There is no cure for Halo Blight, but as it is a seed borne disease only buy seeds from a reputable supplier.
Here's a full list of the varieties of bean and legume plants that you can grow as well as some ideas on pea and bean soil preparation and as well as sowing and plant care.