My thanks for all the replies. I had another look and found ladybugs on the
Japanese maple. On closer examination, I also found aphids, so the replies
were right on target. My local gardening guru, who happened to drop by,
confirmed the diagnosis. She explained the symbiotic relationship between
aphids and ants. I will wash the lot off with water. Tomorrow I will release
a bag of ladybugs and apply a nontoxic spray.

HH

"HH" wrote in message
news
I have a Japanese maple that I have shaped as an outdoor bonsai that has
lots of ants in it. They are clustered at the extremities in the new
growth, much like aphids on new rose buds. Are they harmful to the plant? I
can detect no damage, but then I just noticed them yesterday.

HH