Nick Maclaren wrote:
: In article , Tim Tyler wrote:

:...and *I* meant the ants are "milking" my broad bean tops! They sit
:under the young leaves and eat little black spots in the centres of them.
:I presume they're after the juices, but am not really sure what's going on.
:
:No sign of any blackfly here yet ;-)

: Get a magnifying glass and look harder! As far as I know, there are
: no British ants that do that, and it is almost certain that something
: else is causing the black spots and the ants are after the honeydew
: that the something else secretes.

: I can easily believe that ants would collect the sap where a plant
: has already been damaged, too - it is a convenient sourece of water.
: But most ants have the wrong sorts of jaws to gnaw holes in leaves.

: I can't, of course, say that no species of ant in the UK does it,
: and we would need an entymologist to say for sure.

I can verify that there is no sign of any other insects attacking
the plants.

It's possible that some nocturnal critter is causing the damage -
and they vanish whenever I'm around ;-)

It's also possible that a virus - or some other pathogen is
at work - and the ants are exploiting the damage.

The ants don't make holes in the leaves. There's just black spots on
the undersides on young leaves with ants "licking" the edges of the
spots.

Currently I would guess the ants are wholly responsible - but I don't
really know what's going on. At the moment, I leave them to it.

I know ants do a similar trick of attacking from below when "pollen
stealing" from some plants. I wouldn't put this sort of stunt past them.
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|im |yler http://timtyler.org/