There are two enemies of Beans which surpass in mischief all others, namely the black dolphin and the red spider.
This is the great pest of Broad Beans such as Windsors and Longpods. It establishes itself in the growing tips, and speedily multiplies itself to the extent of several thousands, or even millions. There is no earthly reason why it should do the damage it does, for if the tips of the plants are nipped out and destroyed directly the first fly is seen the enemy is completely baffled. If you do not think one insect worth killing, and wait for a few more to gather, anything may happen. A pinch in time saves nine. It might be thought (1) that the stopping would injure the plant. (2) that the dolphin would strike the plant again. The stopping does no harm whatever, rather good, by helping the plant to swell up its pods; and I have never seen a stopped plant attacked a second time, although I have watched many. In this case the cultivator has the remedy literally at his finger ends.
This is the terror of the suburban back gardener, who sows his Scarlet Runners in 6 inches of gravel and trains them up a sun-baked fence. No matter what the sun or the fence may be like, Scarlet Runners will never have red spider if the soil has been properly prepared for them by trenching. So long as the roots of the plants are luxuriating in a cool bottom the plants are safe. I have never spent a halfpenny on washes for my Scarlet Runners, although the plants are not mulched, except with soil, and never have either water or liquid manure. Red spider is a result of bad culture, and nothing else.