Let's expand this to include other orchids. Some (not all!) of our plants
have a mottled color on the leaves, darker/lighter green. Thick leafed Catts
and some Dends are showing this. Flowering is normal. This does not look
like a fungus in any way, nor does it appear to be a virus. The leaves do
not drop, nor do they develop sunken spots. I initially attributed this to
drops in temperature last winter, but I'm seeing it more. (No severe temp
changes down here in many months.)

I haven't changed feeding regimens; we use Peters 20/20/20 w/micronutrients.
I am not seeing this condition on our Oncidium types. The only two Phals
that seem to be affected are a lueddemanniana and a tetraspis, and those
spots really could be left over from the Mite situation.

So, it's possible that what's causing this is a nutritional deficiency? How
would one determine what's missing?

Diana

"al" wrote in message news:Z22Og.3723$xh3.848@trnddc01...
one *guess* as to the pale chlorotic blotches on thin leaved Phals would
be what Christenson says in his book on page 29, the last paragraph about
"leaves":

"The leaves of many species of subgenus Polychilos show mosaic patterning
of several more or less pallid green shades that may be a result of
nutritional deficiencies in cultivation. Species related to P.
lueddemanniana, in particular, typically produce foliage mottled with
minute sectors of paler green coloration. Although falsely attributed to
a "possible" virus, the cause of this mottling is unknown. Specific
studies should be undertaken to ascertain the possibility of calcium or
other mineral deficiency in this species cluster."

When ever I see this on my thin leaved Phals I think it could also be an
internal "systemic" patch of fugal infection. I have even wondered if
this is something that might be attributed to what my botany teacher
called MLOs so when I read Christenson's paragraph I found it to be a of
relief sorts, I thought, "so it may be normal for the species under stress
and may be a nutritional deficiency."

The buzz words "silvery areas with collapsing tissue" indicate a mite
infection to me, especially on Phals. At least that's what I would treat
for first. I like a miticide called "Ovation" It's stains everything the
unmixed chemical touches a pretty pink color so you know when you have
inadvertently smeared it on things like fingers and drinking cups but it
is known to kill all growth stages down to the eggs. P.S., if you ARE
discovering pink stains on things, you should reveiw the section of the
label that talks about appropriate protective gear when handling this
chemical.

The common name for Tenuipalpus pacificus is "Phalaenopsis mite" but there
is a Tenuipalpus species called T. orchidarum I saw mentioned recently
someplace. I think that is suppose to indicate it lives on orchids. The
mites from the genus Tenuipalpus are called 'flat mites". I don't think
they make webs like the ones in the genus that contains 'spider' mites. I
also think they are about 1/2 to 1/4 the size of spider mites, so they are
tiny and flat and live in the very small depressions that they create from
feeding and tend not to move around much. You need a loop (okay, a loupe)
to see them clearly, unless you have a whole lot of them in which case you
probably found the symptoms first, "silvery bumpy areas followed by tissue
collapse. A heavy mite infestation is almost surely accompanied by
secondary injury from opportunistic fungi and bacteria that enter the
plant through the damage caused by the mites feeding on the weakend plant.
In my experiance I have not found that 'shake the leaf over a white sheet
of paper' trick to work well with the very tiny mites, but maybe that's
just me. Its pretty fool proof with spider mites, if you have enough of
them.

"danny" wrote in message
.. .
I get yellow chlorosis on quite a few of my thinner-leaved phals, without
any other symptoms. Anyone know what may cause that? It doesn't seem to
seriously harm the plant. I also get silvery areas with collapsing tissue
on the bottoms and bases of leaves of all types of phals, which tends to
stop progressing if I hit them with miticides, so I assume that is just
mite damage (which mites hit the phals? I can't see them. They must be a
lot smaller than the spider mites on the catasetums.)

-danny