Allotments 4 All

Hi
I'm new to allotment gardening and have a broad bean problem! The plants are about 10 inches tall, quite bushy but no flowers yet. The top third of the plants - mainly stem- is covered in black. I thought they may be black fly but when I touched it it seemed like dust on my glove. The plants look pretty healthy. Any ideas on what this is and what to do would be greatly appreciated!
Many thanks
Claire

A picture would be handy!

At the moment all I can think of is black fly, and rot due to being too wet and cold.

Have a look at this:
https://www.rhs.org.uk/advice/profile?PID=770
Is this what you have?

What variety is it? Some are more susceptible to blackfly than others. Then some people are saying this is a particularly bad year.

It's black fly.

Take the tops off the plants and for your next years crop, plant seeds in November (they will survive) and you won't get black fly in 2016.