brown spots and ants on fava beans

fraxinus_excelsiorJune 2, 2008

I'm growing fava beans in a container on a second-floor balcony. For a while I'd been seeing one or two ants in them, but I'd never heard of ants being a serious garden pest, so I didn't worry. But this morning they were all over! Even worse, they seem to be eating from these little brown spots that have appeared right at the base of many of the flowers and branches. (photos here )


- What do these brown spots signify? (I assume it must be something, because they're appearing in very specfic locations on the plant.)

- Are the ants the cause of this problem or just a symptom?

- Will getting rid of the ants solve the problem?

- How do you get rid of ants in a container garden?

- If getting rid of the ants won't be enough, what else do I do?

- Should I stop anticipating eating these favas, or is this probably fixable?

Here is a link that might be useful: favas in peril

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tomakers(SE MA Zone 5/6 or ?)

I would bet that the brown spots are aphids and the ants are tending them. Favas are famous for attracting aphids. I am not sure but I think you should try to wash them off with water and possibly soap.

    Bookmark   June 3, 2008 at 3:24AM
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I agree with the above advice. In Britain we call these spots 'blackfly'. They are aphids and the ants 'farm' and protect them for their sweet and sticky residue. The ants prevent ladybirds (ladybugs) from eating the aphids.

These aphids occur largely at the top of the plant and the usual advice is to pinch out the tops after 3 or more flower trusses have developed. The top growth is soft and the aphids love it. Once pinched out, the stems harden and the aphids are much less interested in them.

A good jet of water or insecticidal soap spray (if you cannot bear to pinch out the tops. or in addition to pinching out if the problem is bad) should help keep them under control.

They are selective. One of my patches has them, the other is as yet free from aphids, but I inspect daily.

    Bookmark   June 3, 2008 at 7:23AM
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flora_uk(SW UK 8/9)

Sorry to disagree. Looking at the close up, the 'brown spots' are the perfectly normal blotches at the base of each flower. Those beans look the picture of health to me. Black fly/aphids congregate on the growing tips and are 'milked' by ants. But your beans have no aphids/black fly. I don't know the function of the brown spots but they are normal and I can only assume they exude something the ants like. But you definitely do not have aphids. You can look forward to beans and there is nothing you need to fix. Just keep a look out for aphids in future. Excellent pictures by the way. But you need to recaption them to 'Favas in peak health'.

    Bookmark   June 3, 2008 at 2:26PM
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Thanks, Flora!

    Bookmark   June 3, 2008 at 11:04PM
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