[claireb]

Hi
I've recently acquired an allotment and growing broad beans for the first time.
The plants look quite healthy and bushy but no flowers yet (about 8 to 10 inches tall). On the top third of the plants-mainly stems- is a black layer. I thought it may be blackfly but when I touched it my glove looked like it had black dust on it. Any ideas what this is and if I need to do anything about it?
Many thanks
Claire.

[Hampshire Hog]

Sounds like black fly to me. I would suggest spraying with diluted solution of washing up liquid.
Also suggest you remove the tops of the plants.

Cheers HH

[claireb]

Hi HH
Thank you for replying. I'll try the spraying. Will it matter if I remove the tops even if there are no flowers yet?
Thanks
Claire

[New shoot]

Unless they are a very dwarf variety you are growing, I would spray, but leave the tops on the plants.  At their current height, you would be nipping off all the potential flowering growth.

If it is black dust, it could be sooty mould, which grows on the honeydew that aphids drop. Try checking under the leaves and see if you can spot the aphids themselves, as it is them you need to get the spray onto 

[claireb]

Thanks New Shoot!
I'll try spraying them tomorrow. How much do I mix into the water?
Claire

[JayG]

A teaspoon in a pint of water is about right (if you get foam rather than spray you've added too much.)

Blackfly on green plants are usually hard to miss - it's just possible they may have mostly been and gone - if you don't find many you may be able to wash off some of the sooty mould with plain water from a garden hose.

[Hampshire Hog]

Hi Claireb as per other comments leave tops on if you have no flowers.
Blinked and missed that!!
Cheers HH

[AK9]

why do you recommend removing the top of the plants?

[New shoot]

why do you recommend removing the top of the plants?

The young tender tops of the plants are very attractive to blackfly so if you take them off, you can help control the problem 

[claireb]

Thanks everyone!
I've just been up to the allotment and sprayed them! Hopefully that will sort them out. I've actually got a few flowers now but I'll see how I get on with soapy water before taking the tops off.