Mushy brown spots, pitting on Phalenopsis leaves - please help!

[pluto889]

Hi guys! I’m new to this forum and a new orchid owner, but I’ve been lurking here for quite some time. I’m hoping you guys can point me in the right direction as to what’s happening with my phal Guadeloupe Pinidae. As the pictures show, two of the leaves have recently developed some rather large mushy brown spots. The spots have pitting on the underside of the leaves, and the pitting is white; i don’t know if it’s insect eggs, or fungal, or too much sun. I am making a organic pesticide using neem oil and some peppermint Castile soap. Should I spray it on? I currently temporarily have the orchids outside, until the LED grow lights I have purchased arrive. I live in Ontario, and we’re getting some hot sunny days recently, but I’ve tried to keep the phal out of direct light as much as possible. Thank you!!

[dinvy]

Looks like heat/sun burn. I'm also in Ontario and some of my plants burned, it's been an exceptionally hot july.

[jldriessnack]

So, If you have been leaving it in direct sun, it is likely just sun burn which, aside from being ugly, is not a big deal. Be careful about applying neem in hot weather. If it is over 80F you should not use neem unless it is over night.

I find that hydrogen peroxide is good against bacterial attacks on phals, and if it is fungal, neem WILL do the trick.

To see if it is a bact/fungal attack, make note of the margins and see if they expand within 24 hours. If they expand then it is likely bact/fungal. But if they remain the same and begin to dry out in short order, like in 2 days, then it is probably from the sun. Phals really should never be exposed to direct sun in summer.

[SouthPark]

Pluto ------ describe the growing conditions there. Is the orchid exposed to intense or direct sunlight? And temperature range. Indoor or outdoor growing. Any natural and gentle air-movement in the growing area? Do the leaves get wet any any stage? In nature, leaves certainly do get wet sometimes - or even a lot. But sometimes, for home growing, water or moisture on leaves can bring on certain kinds of unwanted fungal activity ---- and air-movement and keeping leaves fairly dry can help avoid some issues.

If you do have fungal and/or bacterial activity on the leaves - then may a copper spray for plants can help here. Or a systematic fungicide for orchids (eg. monterery garden phos).

For protecting against insects ---- neem oil etc --- ok .... but will likely need to keep the plant out of direct sunlight, and maybe not apply on hot days ---- as the oil can get in the way of leaf cooling ---- possibly resulting in dying leaf cells.

[estación seca]

Welcome to the Orchid Board!

That's sunburn. 2 minutes of hot sun can do this. Phals are shade plants. Move them where they will get no sun.

[Carebear2]

few votes for sunburn.

I will put in a vote for no sunburn. I know I live in the UK but I have caused a fair bit of sunburn too and mine always look distincly more "burnt" and yellowing
Sunburn does not cause white spots on the underside of leaves, that could be something like mealybugs but the picture is far too small to identify so a closeup is needed although the majority think it is sunburn so if it has been in strong sun maybe that is all it is

[Ray]

As there do not appear to be any wounds that would permit an adventitious infection, I’m voting for sunburn as well (and I have seen such spotting occur up the undersides of burned leaves, especially in newer growth).

Do not treat it with anything; those spots will turn parchment-like in short other.

[Roberta]

I do think that it sunburn. Unslghtly, but the undamaged part of the leaf can still photosynthesize so don't cut! Eventually (may take a few years) the leave will drop after there are new ones to take its place. Orchids don't do anything fast, so patience!