On Sat, 07 Aug 2004 11:47:16 +0100, Stephen Howard wrote:

On Sat, 07 Aug 2004 11:12:46 +0100, Dougie Nisbet
wrote:

My Willow tree is swarming with wasps. I can't really see why they're
there, and what they're doing. The willow is covered in black aphids but
the wasps don't seem interested in them. The wasps just land on the
leaves, walk about a bit, then fly off. What's so attractive about willow
for wasps?


Aphids exude a sweet, sticky substance called honeydew - I expect the
wasps are attracted to it in the same way as they're attracted to the
traditional wasp trap...jam and water in a jar.


That was my first thought (I've seen the ants milking the greenfly on some
other plants) but I can't see any indication that this is happening. You
could be right though. I've not come across black aphids before and
they're a bit bigger than their green friends. The wasps land on the
leaves and don't seem to go near the aphids which are massed around the
stems.