John Savage wrote:
"jim" writes:

Harlequin bugs are notorious for attacking citrus, they suck the sap out of
new growth and it withers. Hard buggers to get rid of, you can either spray
but need to thoroughly to get them as they hide under the leaves. I do it
the tried and true way. Firstly you need goggles and rubber gloves and old
clothes or overalls and a pair of tongs, (these bugs when you threaten them
they squirt and acidic and very smelly liquid at you) have a bucket of water
handy and when you catch them drop them in it and drown them, eventually you
will get them all, do a little bit each day.


This is exactly how I'd describe the bronze citrus bug. Are you sure
that Harlequin bug is the correct name for the pest you are describing?
Bronze citrus bugs/beetles start off as tiny and green, as they grow they
turn orange, and in their mature winged state they are flat and about the
size of a Christmas beetle, but matt black and quite menacing-looking.
These can squirt acid when grabbed.

The damage does sound like these (harlequin bugs are different- brightly
coloured and the most common one attacks cotton and its relatives, not
citrus). I am surprised you can't see any. Look closely for tiny
entry/exit holes, as you could have a tip mining moth, though I don't
know of one that attacks citrus. Other than that, I'm stuck

A grub that likes citrus tips is a black and white one which looks like a
bird turd on the leaf. I don't know what sort of butterfly it develops
into, but in the grub stage it can devour a lot of leaf in one night. You
will often find them under a leaf during the day, near a site of leaf
damage. Pick off and squash.


That one grows into the citrus swallowtail butterfly- very attractive
beast, but a bit too voracious to leave on small trees.


Aphids like the red/green tips of citrus, and can congregate there in such
numbers as to totally cover the new foliage. The OP should look closely
to see that these are not the source of the tip problem.

Cheers
Dave