Orchid Culture - 2014 Questions & Answers
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Dendrobium Flower Spike Split
Q. My dendrobium flower spike split in two, one is larger and the second one is substantially smaller. I was wondering if I should cut the small one off.
A. Don’t cut off the second spike, that’s how healthy and happy dendrobiums should bloom!
Discolored Phal Leaf
Q. I am seeking assistance with a phalaenopsis that has been an otherwise vigorous and healthy grower. My suspicion is that it is a micro-fungal infection. Should I remove the leaf also or at least the affected part?
A. When I first saw the affected leaf, I thought hmm, chlorotic streaking, could be virus; but the bottom of the leaf just had red pigmentation, and the whole plant looked like a healthy and vigorous grower, so maybe that’s just an old leaf? Cut off the affected part of that lower leaf, spray some peroxide on the wound and see what happens. The redness may suggest a little supplemental magnesium might be in order, say 1/2 tsp/gal or so once a month in case your water is magnesium deficient, but that plant is a very happy camper. If you start seeing the chlorotic streaking in the upper leaves, then you might think some sort of viral infection, but your bottom leaf might just be fading off into the sunset. Looks like you do a great job growing under lights!
Funnel Shaped Leaf
Q. My orchid has a funnel shaped leaf with the new leaf growing inside it. I am worried about how this will pan out as it continues to grow. Should I do anything?
A. Hopefully that is just a strange leaf mutation and the next leaf will grow out normally and cover it up. It’s also possible it could be a genetic deformity or a response to a strong chemical application.
Cold Damage on Phal
Q. I think I may have damaged my phalaenopsis when I left the window open when it was 50F outside. The problem doesn’t appear on the part of the leaf that was protected by the leaf above it. But it could be virus too, what do you think?
A. I think your instincts are correct, cold damage. That does not look like a virus to me. 50F is cold, but not that cold unless they were very used to be warm and cozy in the indoor environment. Usually temperatures of 55F to 60F are a good chill that encourages your plant to start thinking about sending up a bloom spike. Pour some hydrogen peroxide over the leaf so no secondary infection sets in. If it starts getting soft or mushy, you may have to remove the leaf.
Vanda Leaf Edges Serrated
Q. I have a new vanda orchid and I noticed the leaf tips appear serrated. My other vandas are either smooth tipped or have small irregular edges but not as extensive as this one. Is there a problem?
A. No worries, that’s just the way some of them look. Your plants look great!
Vanda Potted in Coconut Fiber
Q. I bought this vanda orchid 2 weeks ago potted in coconut fiber. I decided not to repot it because it looked so healthy and it was in bloom. Recently I noticed the tips of the small roots started shriveling and two of the large root tips turned brown/black, so I decided to take it out of the pot and examine the roots. The three large root structures that were in the air look fine but all the roots that were potted in the media are yellow or brown. I haven't watered the plant at all (it rained once) since buying it but I did spray the exposed roots a couple of times.
A. I think you should get that new vanda acclimated to your growing conditions. If the plant had been in that pot for a while before you
bought it, the person growing it must have had it acclimated to his
growing conditions because the roots were nice and fat.
I think you were right to pull it out of the mix and hang it with your other vandas. You could put some spanish moss around the roots to help keep them
hydrated in that they were probably accustomed to the wetter conditions in the pot. Ultimately the plant will adapt to your cultural practices. It's a nice healthy plant with lots of good roots.
What is Eating my Flower?
Q. I found a Cattleya bud that looks like it has been eaten through the center of the bud. I have seen some insects before but I am not sure what I am looking at in the picture.
A. Slugs or snails maybe? You can bait the the plant at night with some apple or potato slices and see if you find the guilty party in the morning. It is also possible that cockroaches are dining on your flower, spread some boric acid appetizers around and see if you find some dead cockroaches. (Nov-14)
Plant is Dead in the Middle
Q. What should I do with this cattleya plant? This one re-bloomed once but one of the new shoots does not look good. Hope I can save the other.
A. That plant needs to get knocked out of the plastic pot and all the mix washed away from the roots. Cut away the dead center and sickly side and drop the remaining healthy tissue into a clay pot with no mix and just watch it, watering every other day or so to see if new root growth begins. You can apply a root stimulator like seaweed or rootone to encourage new root growth. Once you see new green root tips, drop it into a pot with your potting mix of choice, maybe a 4 inch pot. You'll have to make a decision about whether or not to use sphagnum moss. Some people have learned how to grow in sphagnum which I think means they have learned not to water plants until the sphagnum moss is almost dry, and you can tell when sphagnum is watered too much cause it’ll grow algae on top. Unless you can resist the temptation to water, another potting mix may work better for you and your growing conditions. (Nov-14)
Vanda Stem Hanging Downward
Q. My vanda is about 17 years old and blooms 4 times a year. The main root ball is totally meshed into its small, original wood basket. I'm hesitant to undo any of the root ball and replant it in a bigger basket. I'm worried because the bloom is now almost touching the ground. Should I just try to hang it higher up in the tree? The smaller, off shoot roots seem fine and the main shoot is hard and tough.
A. That sounds like a wonderful vanda. I think I would try to retrain it. Vandas are monopodial orchids, that simply means they grow upward, adding a leaf or two or three every year at the top of the plant and losing a leaf or two at the bottom. The bottom of the plant will either get woody or sprout new keikis (babies) from the base and the keikis are often the future of the bottom of vandas.
The way yours is growing, the top part looks like the viable part though it may not have enough live roots to support itself. Maybe you can patiently reorient the plant so the top part is growing upward. Get a very long S hook and tie the top of the plant to it and find a place where you can hang the S hook so the top of the plant is vertical without separating the top from the bottom plant. Ultimately is will sprout new roots, that you can encourage with rooting hormones if you are so inclined, and some people tie some sphagnum moss along the stem to encourage root growth. At some point in the future you'll be able to separate the two pieces and your vanda will be vertically oriented, like your other vanda.
Hung Sickly Cattleya in Tree
Q. I got this C. mossiae var. coerulea in 2009 and it never did well. New leaves got black tips that moved down toward the pseudobulb. I hung it in an oak tree next to the driveway 2 years ago. Never did anything to it in the winter. Squirrels chewed on the pseudobulbs. I would put a little fertilizer on it 2-3 times a year. It got water whenever it rained. Upon returning from a trip early summer, something caught my eye as I got out of the car, two nice blooms.
A. Perhaps our orchids are more resilient than we think they are! I’ve killed some testing their winter tolerance, though some bloom better after the winter chill.
Maggots on Bulbophyllum
Q. Are these maggots crawling on my Bulbophyllum Wilbur Chang?
A. It is the larval form of some critter. It could be maggots given that flies are the natural pollinator of bulbos. Yuck!
Q. I was wondering if you could help me diagnose what my phalaenopsis is suffering from?
A. That bottom leaf has edema
, which is caused by watering late in the day when the night turns cool or by watering on a gray/cloudy day. Basically the plant takes up more water via the roots than it can shed by the leaves, so it forms a blister. Just leave it alone, it won't cause any further damage and hopefully is hidden by the leaves above it.
Phal Leaf Translucent
Q. My phalaenopsis has spotting on the leaf and it looks like it is turning transparent underneath. How do I treat this?
A. That looks like the beginning of a bacterial infection
, that often happens during the hot humid summer season. Pour some hydrogen peroxide over the leaf and watch it. If the spot becomes sunken and water soaked, you'll have to cut the infection out. Make sure there is plenty of fresh air bathing the plant and try not to let water stand on the leaves.
Lanky Weed-like Orchids
Q. I have been given the task of saving these orchids for a friend. I don't even know what they are. Any info you have would be appreciated.
A. I think those are reed stem epidendrums. Some people actually grow them in the ground, although they may need protection from cold at temperatures below 40F. I put them in a pot with a tomato cage type wire structure around them to hold them up. You can use your choice of potting mix, whatever works for your other plants.
Phal in Pot with No Drainage Hole
Q. I got this as a gift in 2 months ago. I only watered it once so far and did not realize that I over watered until seeing the purple flowers drop. I flipped over the pot and there was actually water flowing out! Apparently it affected the purple side only.
A. I think the phal with the pretty purple flowers has crown rot and is probably is not going to make it. Sometimes "arrangements" are sold where plants in individual pots are combined into a larger pot with a decorative moss topping and no drainage.
As you have found out, this makes them "disposable" like cut flowers because the plants will not grow well without drainage.
If you pull the plastic pots out, you can water that separately and after watering it, drop them back into the decorative pot. Better yet, keep each plant in its own pot with a drainage hole.
Zygopetalum Dropping Flowers
Q. I bought a Zygopetalum about a month ago. It has been doing well at our bay window facing south-east where I keep all my orchids. All of a sudden all the flowers started to drop one by one and I noticed some browning on the leaves and stems. Is this a sign of some disease?
A. You got a month of pleasure from the flowers. That’s about how long they bloom so don't be concerned about the flower drop. The brown streaking on the leaves is not a good thing though. I think it is perhaps bacterial because it looks a little sunken and has the yellow halo around it. Get some hydrogen peroxide out of the medicine cabinet and pour it over the leaves, maybe tip it over the kitchen sink so the peroxide doesn’t drip on the roots. Cut the old flower spike off at the base. You have a nice healthy new growth, and that is the future of your plant.
Q. I recently acquired a terete vanda when its host plant was cut down. I have put it into a pot with coco husk chunk and dried twig. It is in bright but not direct sunlight and is watered daily in the morning. It is shriveling. What am I doing wrong?
A. I bet the plant just has to adapt to its new home and grow new roots. You could spray the plant a couple times a day until it grows new roots. Good quality cypress mulch is another good option for potting up terete vandas.
Bulbous Growth on Phalaenopsis
Q. I have a one year old phalaenopsis which is flowering beautifully. The first few blooms are just beginning to drop but the first one to wilt has not yet dropped. Instead it has dried out completely and the stem has developed a large, hard, elongated bulbous growth on it. What do you think it is?
A. I think your orchid has been very naughty and is in a family way. Seriously, that is a seed pod. I think I’d remove it cause it will use up the plant reserves to produce all that seed and you don’t know who the daddy is so you probably don’t want to go through the 3 to 7 year period of raising the orchids from seed to bloom time. Beautiful phal you have!
Emerging Growth Rotted
Q. The new leaf on this cattleya rotted. Is this black rot?
A. No, the green sheath or cataphyll on the emerging growth created a pocket in which water collected. Bacteria grew in this water pocket and rotted the new leaf, the same basic mechanism that causes crown rot in phalaenopsis. Whenever you see a pocket form, gently peel it back so any water or condensation will drain freely.
Water Soaked Yellowing on Cattleya
Q. I am seeing yellow discoloration on some of my cattleyas and it seems to be exuding liquid. What is wrong?
A. That is the dreaded black rot, a scourge for our cattleyas in the heat and humidity of summer in Florida. Some have found that supplying sufficient calcium to their orchids will prevent black rot, but I use many calcium supplements and still have a few cases of black rot each year. The yellowing in these two cattleyas is coming up from the pseudobulb and into the leaf, and it moves fast, destroying a growth in a day or two. Excise infected tissue with a sterile tool, disinfecting between cuts. If you have access to Banrot or Subdue, pour these super duper fungicides through the pot. Otherwise pour hydrogen peroxide on the cuts and keep the plant on the dry side for several weeks.
Sunburn and Then Secondary Infection
Q. I put this phalaenopsis outside hanging off the balcony, so I imagine it is sunburn. I was wondering what to do about it and now it's getting worse. Do I just let the leaf shrivel and fall off?
A. That looks like the leaf got sunburned from the sudden exposure to higher light than it was used to while it was in the house. Inside light levels are dramatically lower than outdoors locations, even if they seem like they are shady. The wound caused by the sunburn then got invaded by pathogens, probably bacteria, that are quickly infecting the entire leaf. Usually you would removed the infected tissue an inch below the obvious discoloration, but I think you should simply remove the entire leaf with a single edged razor blade and then pour hydrogen peroxide over the cut. Hopefully it will grow a replacement leaf before the summer is over.
Keikis on Top of Cattleya Pseudobulb
Q. Anonymous is an orchid I've had for two years, and in the past month it has started growing keikis at the top of the pseudobulbs. Is this a good sign or the orchid doing its darn best to get the heck out of the broken down media? Is it already too late in the year to repot?
A. It's fairly uncommon for cattleyas to form new plantlets at the apex of the pseudobulb, but apparently Anonymous hasn't been reading the orchid books. Whether the new plantlets formed because of its genetic background or as a last act of defiance, the new growth looks very healthy and happy. I'd pot up the new plantlets as they may be the future of this plant. There is still plenty of time left in the growing season for plants to reestablish themselves after repotting.
Dendrobium Coming Back to Life
Q. I thought this dendrobium orchid died about three years ago but over the last year it just began sprouting again.
I recently found some white spots and a yellow spot on some of the orchid leaves.
I live in the Caribbean where it is usually hot and dry from the end of January to mid-May and from mid-May to January it is very rainy. The orchid is outdoors.
A. Dendrobiums tend to like being in very small pots with a largely inorganic mix. I’d think about putting it in a much smaller pot in bright light with lots of air movement, someplace that is close to your hose so you can give it a drink during the droughty season. That leaf spotting looks pretty minor, I wouldn’t worry about it.
Better-Gro Bag Babies
Q. I bought these two little Better-Gro orchids at Lowes: Scheherazade Cluster Red and Fire Dance x C. lawrenceana Orange. Are these miniatures or are they babies? Are they cattleyas?
A. These are seedling cattleyas rather than miniatures. The first one might be C. (previously Slc.) Scheherazade , but it is more likely the much more commonly available Ctt. (previously Slc.) Dark Waters 'Scheherazade' AM/AOS. The "cluster red" refers to the shape and color of the flowers. The second one is the unregistered cross
Ctt. (previously Lc.) Fire Dance x C.
lawrenceana where the "orange" refers to the color of the flowers.
Water Soaked Blight on Flower
Q. I discovered the flowers on my Dtps. I-Hsin Song had a growth on them. The damage to the flowers started on the outside of the petals. Since there were eight flowers with this damage I assume that it is contagious and moving fast so I removed the flowers and isolated the plant. Could you identify what is causing this oozing wilt?
A. I didn’t recall seeing this kind of floral damage before so I strolled through the greenhouse looking for something similar. Low and behold, a newly opened C. skinneri alba had similar blighting.
A few conversations with Ruben Sauleda and Phillip Hamilton while at the Redland suggested this to be a bacterial infection, particularly with the observation that the flowers smelled bad.
Removing the flowers containing the infection is the first step. Consider spraying the plant and those around it with one of the copper compounds like Kocide or Phyton 27 (remembering not to spray dendrobiums or anything in bloom with copper) or spray with something containing quaternary ammonium compounds like Physan or pool algaecide.
Then evaluate whether increased air flow can be provided to prevent recurrence.
Floppy Phalaenopsis Flowers
Q. I bought a beautiful phalaenopsis two months ago that seemed super healthy, I was watering it with a shower once a week after checking the dryness in the middle of the pot (the pot is quite small, though). Suddenly, one by one, some flowers began to get floppy. My first thought was the flower needs humidity, so I sprayed the petals with lukewarm water a few times a week, but that didn't seem to help. Any advice?
A. It’s possible the plant is nearing the end of its natural blooming period, but those flowers don’t look like they are aging normally. More likely, the plant is a little dehydrated, as also can be seen in the wilted leaves. It can be dehydrated because either it is not getting enough water (it should be watered until water runs out the bottom of the pot when it is watered) or because the potting mix and possibly the roots are degraded so they can’t absorb water (knock it out of the pot and you’ll be able to tell by looking at the roots). In a follow up note, she wrote “the bark was so tight the roots were suffocating, so I repotted and am trying to regrow them.”
Repotting a Compot
Q. I have ordered some compots that will need to be repotted. What is the normal way to repot baby plants? Do I need to sanitize them?
A. Community pots, or compots, usually contain anywhere from 10 to 25 plants and there will likely be several large plants, some medium size plants and some runts in the pot. Get the best quality sphagnum moss you can find, some styrofoam peanuts and small clay pots, like 1” or 2" clay pots. Once the plants in the compots are totally overgrown in the compot, you’ll take them out, wrap some sphagnum around the roots and drop the plant in a tiny clay pot. Clump the runts together into a second mini compot. You can treat them with fungicide (like pool algaecide) and root stimulator (like Superthrive) as a soak before repotting or as a drench after repotting.
Black Marks on Vanda Leaves
Q. What is causing these black marks on my vanda leaves?
A. That is the bane of the vanda grower's existence, the dreaded Thai crud, caused by the fungus Guignardia.
The black diamond shaped lesions that feel like sandpaper are actually the spores getting ready to spread more fungal disease around your collection. Some people coat the lesions with clear nail polish (closing off the stomata in the process), others remove the leaves to remove the source of infection from spreading to their other plants. Once thought to be incurable, monthly spraying with the specialty systemic fungicide thiophanate methyl will help exclude this fungus from your collection. You can order 6 oz of Thiomyl on-line for less than $30.
Phalaenopsis Roots Where Flower Spike Should Be
Q. I have a white phalaenopsis that has roots coming out where the flower spikes normally emerge. During the flowering season there were three separate sprouts in between the leaves that would normally be flowers but ended up being roots. Can you give me an idea what is causing this?
A. Roots forming between leaves is perfectly normal. Phals are monopodial orchids which simply means they grow upward along a stem with new leaves emerging at the top and new roots and flower spikes from along the stem between leaves. If your plant is only throwing off new roots rather than flower spikes, perhaps it did not receive the low night temperatures this past fall that are the signal for the plant to form flower spikes. Let your plants chill down to 55F at night for 2 or 3 weeks during the Halloween cold snap we always seem to have and then bring them inside to their winter home. You should see flower spikes by Christmas and flowers by Valentine's Day.
Schombocatt Flower Spike
Q. I bought this Smbc. Mem. Louise Fuchs 6 years ago from Paul Storm when he did a program for SAOS. The spike is 15" long. What is this thing going to do?
A. It’s going to flower and look like this. This is a primary hybrid between Schomburgkia (now called Myrmecophila) tibicinis and Cattleya bicolor. The flower spikes are thick and a large cluster of flowers will develop. Schombocatts take a while to fully develop their flower spikes, but the floral reward is worth the wait!
Central Heart of Phal Damaged
Q. I received this orchid as a gift. It was repotted just last week and I cut away a few brown roots which I think may have been the problem. I wasn't watering more than once a week but it may not have been drying out completely in the center of the pot. Will it recover?
A. Phals are monopodial orchids, which means they grow up from a central heart. If you look down at your plant, you'll see that the heart of the plant from which the next leaf would ordinarily emerge is dead. Your hope for that plant is that it will sprout a keiki from the base of the plant. It probably would have been more likely to sprout a little plantlet if the roots had not been disturbed by the repotting, but it may still sprout a keiki. What is the orange thing sticking in the pot, you aren't adding ice cubes are you? (Apr-14)
Phal Bud Blast
Q. This phal had been developing fine and growing buds, until they stopped growing and then faded. Now there are little drops at the end of the stems (and even if I wipe them, they grow again).
A. I suspected spider mites and advised her to take the plant over to the kitchen sink and spray it thoroughly with lukewarm water and then get a spray bottle, fill it with water and a couple of tablespoons of dish soap and isopropyl alcohol and spray the entire plant, top and bottom leaves and flower spikes (but not the open flower).
I thought a weekly Saturday night bath would help take care of the mites.
I asked for some close up pictures, and her pictures showed really healthy plants with beautiful leaves and no stippling (mite damage).
Instead of mites, I think the buds got too close to the window during our recent cold weather and the cold weather caused the buds to blast.
A Saturday night bath and soapy water and alcohol spray are good for your plants while they are indoors. (Apr-14)
White Round Things in Orchid Pot
Q. I have recently discovered some white round shaped things inside my orchid pot and I have no idea what they are. Can you tell me if something is wrong?
A. See if you can fish out one of the little white balls. If it’s hard and crunchy, it’s probably time release fertilizer that was incorporated into the mix. If it’s soft, it might be a spider or insect egg sac, but I’m guessing it’s time release fertilizer.
Should Sunburned Orchid Leaf Be Removed?
Q. These orchids got sunburned when I moved them into their winter growing area. Should I remove the damaged leaves?
A. Sunburned leaves may or may not have enough undamaged areas that they can still generate energy for the plant. The sunburn is unsightly and can provide an entry point for fungus and bacteria.
The sunburn on the first leaf is just dried up, the top half of the leaf could be removed with a sterile single used razor blade to remove the unsightly leaf burn, dusting the open cut with cinnamon or a fungicide to prevent introduction of pathogens.
The second leaf looks like it already has a secondary infection, so perhaps it's best to remove that entire leaf.
Brown Bumps on Orchid Leaves
Q. I am a newbie and recently found problems on my phal leaves. The affected plants are still doing well and some are still flowering. Can you identify the problem?
A. This is the time of year we start seeing edema on orchids. Edema is like a water blister that forms because the orchid has taken up water faster than it can be shed from the leaves through transpiration. It happens when you water too late in the day and it turns cool at night or when you water on a gray or rainy day. It is a leaf blemish that will never go away but doesn’t do too much damage to the leaf.
Dendrobium Leaves Yellowing and Dropping
Q. My new owner is trying to kill me! Is there any way to save me?
A. That is one of the phalaenopsis type dendrobiums that is very sensitive to cold.
They really don't like to drop below 50 or 55F and would prefer to stay above 60F.
Leaf drop can also be caused by too much or too little water, though the recent cold snap is probably the culprit here.
The good news is that the plant will grow a new cane with new leaves in the spring and be ready to bloom again next year.
Flower Spike Trapped Under Leaf
Q. This flower spike is trapped under the phalaenopsis leaf. Would you recommend that the leaf crowding the spike be removed?
A. I wouldn't remove the leaf, the spike will eventually grow around it or through it. You could slowly and gently try to insert a plant tag or something very thin between the spike and the leaf to encourage the spike to go around the leaf.
Orchids in a Bag
Q. I just bought two cattleya plants at Lowe's. They're both from Better-Gro in in square pots about two inches high. Will I have to wait years before they develop a flower since they're pretty tiny?
A. Yes, you'll have to wait a bit. I have bought loads of their little plants and they do grow up and bloom beautifully. You can maximize their growth rate by making sure they get plenty of light, water and fertilizer during the growing season, but you're probably at least 2 and maybe 3 years away from blooming. Good things come to she who waits!
Can We Grow Paph. sanderianum Here
Q. I have heard that the beautiful multi-floral paphiopedilum Paph. sanderianum requires a bigger day night temperature change than we typical get. Can we grow it here?
A. Orchid Prof Courtney Hackney, who often brings his multi-floral weeds to the Show Table, responds: I had always read that Paph. sanderianum was hard to grow, but it is one of the easiest paph species based on the ones I have. I bought two seedlings from Carter & Holmes in 2” pots in the summer of 2007. One is blooming for the 4th time, and was divided last year so it skipped a year. It has three fans growing now, one is coming into bloom and I expect the others will also bloom by the end of spring. The second plant has not been as vigorous, but has bloomed twice and has two or three fans that will bloom this winter/spring. I have them growing in lava rock and in plastic pots. Of course, they get a tablespoon of dolomite lime every month. The only reason I ever repot is because they outgrow the pots and push up so much that they become top heavy. They love the climate here as do all of the multifloral paphs.
Something Eating Vanda Flowers Overnight
Q. Richard Bergeron from New Orleans City Park Botanical Garden wonders what is eating the flowers on the vandas he hung in the orchid conservatory.
A. I wondered whether it was mice or cockroaches and asked Courtney Hackney, who responded: It looks like roaches to me, but there may be something else at work in New Orleans. Mice always go for the pollen and if they do eat the buds they go right for the pollen first and I bet rats are the same. My money would be on roaches. Roaches in New Orleans rival those here.
Phalaenopsis Only Has One Flower
Q. Do you know why my phalaenopsis only has one flower?
A. That single bloom looks like it's coming from the prior year's flower
There are two schools of thought on cutting the phal flower spike when it is done
blooming. One school says just cut the spike back a
couple of nodes and the old spike will rebloom, and that's true, you may get
a few more flowers from the old spike. The other school of thought says cut
the old spike off at the base of the plant after it's done blooming and let the plant gather its
strength over the summer to have enough energy to throw a new flower spike
around Christmas so that by Valentine's Day, you'll have a full flower
spike. I'm of the second school of thought.
Yellow Spots with Brown Centers
Q. I just brought my orchids inside for the winter and noticed these yellow spots with brown center on several of my phals. Can you tell me what it is?
A. That looks like bacterial brown spot. Pour hydrogen peroxide over the spots, if they don’t enlarge, the bacteria are dead and won’t spread. The wounds will never heal, but it’ll grow new leaves in the spring. A spray with a copper compound (kocide, liquid copper, etc.) is a great preventative and a great cure, you can spray in the fall when weather starts to cool to protect them and you can spray now to kill the bacteria. Just don’t spray dendrobiums with copper.
Dark Splotching on Thin Leaved Orchid
Q. My orchids seem to have some disease?
A. That looks like a fungal infection, possibly caused by Cercospora. Spray it with one of the copper fungicides or a fungicide containing thiophanate methyl (like Thiomyl, Banrot and Cleary's 3336). You will also have to think about what you can do in your growing area to increase air movement, particularly of fresh air moving over the leaves so your plants will be less
be susceptible to infection from fungi and bacteria. Plants really crave lots of fresh air movement over the leaves.