Orchid Culture - 2013 Questions & Answers
by Sue Bottom, from the St. Augustine Orchid Society Newsletter.
Email us with any orchid question, if we can't answer it we'll find someone who can! Send photographs too!
White Cottony Blobs on Orchid
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. Those are mealybugs. Pour some isopropyl alcohol into a spray bottle and spray the plant from the top of the flowers down to in between the leaves. You won't kill them all because the babies are hiding in the crevices of the leaves. You'll either have to repeat the treatment every week or pour an insecticide drench through your potting mix. If you have some of the Bayer product containing imidacloprid, use 1.5 teaspoons per quart for the 1.47% strength imidacloprid product or 4.5 tsp/qt for the 0.47% strength product.
Winter Care of Seminobile Dendrobiums
Q. In March I bought a beautiful orchid that had flowers cascading down both sides of the stalk. I was told to stop watering it in November. Now what?
A. That sounds like one of the soft cane, deciduous dendrobiums, probably one of the seminobiles. They like a cool dryish winter rest period with no fertilizer after Thanksgiving. They can be chilled down to the upper 30's and watered infrequently, maybe every second or third week, just to keep the canes from shrivelling. They may lose their leaves, but this winter stress encourages bountiful spring blooms.
Black Leaf Tips on Dendrobium aggregatum
Q. This time last year some of the leaf tips on my Den. started turning yellow with slow progression toward the pseudobulb. It is happening again this year. Some of the leaves that I cut about one inch below the yellowing last year are visible in the photo and you can see the cut leaves are in good shape. Any idea what is causing the yellowing?
A. I think that’s anthracnose, you can see the advancing edge and the concentric rings. Cut away the infected part of the leaf well below the affected area, spray it with thiophanate methyl (like Thiomyl, Banrot and Cleary's 3336) and then drench the root ball. Maybe you should keep it a little drier this time of year so the plant can have the cool dryish rest period it likes.
Black Sheaths at Base of Cattleya Pseudobulb
Q. This is my second year growing orchids and I just noticed black spots and growths at the base of some of my cattleyas. I suspect it is black rot. Can you help me diagnose this problem and recommend treatment?
A. Your orchids are perfectly fine, you are seeing the blackening of the paper sheath rather than blackening of the pseudobulb itself that would be indicative of black rot. The papery sheath protects the new growth as it emerges from chewing insects and provides some structural support.
As the pseudobulb matures, the papery sheath is no longer needed and can be peeled away from the pseudobulb. This is often a good practice because pockets can form between the pseudobulb and the sheath that can accumulate water in which bacteria can proliferate and this can cause rot.
You have normal senescence (die back) of this papery sheath, simply peel it back away from the pseudobulb. As long as the pseudobulb is green and hard (not soft and mushy), you have no problems.
Katydid Eggs on Orchid
Q. I have seen several types of scale on orchids, but never one that looks like this. It’s on the bloom spike of an Epi. secundum that summers outdoors. Am I correct in identifying it as some form of scale?
A. Kathy, the author of the question, and I agreed it was like no scale we had ever seen and we postulated it was more likely to be insect eggs. Kathy did a little searching and found the answer, they’re katydid eggs courtesy of the
Missouri Botanical Garden.
Speckling on Underside of Leaves
Q. Although the leaves of my phal are growing and the plant looks healthy, I have noticed a brown speckle on the leaves of my orchid. The coloring is also under the older leaves, what is it?
A. That speckling is purplish pigmentation which suggests your plant is in good bright light. That is a good thing! It is the equivalent of you developing a tan. You and your plant should both be happy!.
Just Add Ice?
Q. My friend cared for my healthy orchid while we were on vacation and now there are dead spots on the leaves, but it can’t be sunburn because some leaves that were under other leaves exhibit the same damage. Also, the newest leaf has a soft tip. My friend has a sun room full of other plants. I told her to simply give the plant an ice cube now and then. I suspended a funnel to place the ice cube in so it would not touch the plant.
A. That leaf damage is from the ice cold funnel and water causing mesophyllic cell collapse on the phalaenopsis leaf, like what happens in the fridge when your vegetables are placed too close to the freezer section.
Some people have told us they use ice cubes to water their orchids and there is even a website dedicated to this.
I’m guessing the successful ice waterers are growing only phalaenopsis orchids potted in sphagnum moss inside an apartment or condo where watering is a chore.
Adding such a minimal amount of water each week would be a way of keeping the sphagnum moss moist but not wet. This would be one way to solve a problem many growers encounter.
Watering plants growing in sphagnum moss too frequently causes the moss to stay sopping wet so the phalaenopsis roots suffocate and the plant ultimately dies.
However, your plants enjoy an ice bath almost as much as you do. It’s better to learn to water your plant only when the moss approaches dryness, even if that means you don’t water them every Saturday morning. If your moss is still wet on your normal houseplant watering day, simply skip watering your phal that day. When the moss approaches dryness, water the plant thoroughly with room temperature water, let the water drain from the pot and then don’t water it again until the moss once again approaches dryness. Some growers simply repot their plants in a more freely draining mix after the flower is spent. (Nov-13)
To Divide or Not to Divide?
Q. My dendrobium has a huge new growth, is it possible to separate the plant or should I leave it as one big plant?
A. The new growth looks terrific, your plant is very happy! Dendrobiums are one of the few orchids that will bloom from old growths, so you should get flowers on the old and the new growths. If you keep it together as one big plant, you’ll have more blooms per square inch of bench space, and room for more orchids too! (Nov-13)
Leaf Loss Suggests Problems with Roots
Q. Over the last two weeks, I noticed this Dendrobium farmeri kept dropping leaves from its new growths, after growing vigorously all summer long. Why did I wait so long to investigate?
A. I forgot my cardinal rule. When a plant starts dropping lots of leaves, cherchez les roots! Once I came out of denial I took a hard look at this dendrobium growing in a wooden basket with no potting medium. Much to my surprise, there was snow mold digesting the wooden basket and suffocating the roots in the process.
As the roots were getting killed, the leaves on all my new growths started to yellow and drop. To fix this, the wooden basket was dismantled from the bottom up, first cutting the metal wires that hold it together and then prying the rotting wooden slats apart one by one. There was a little root damage along the way, but the roots were happy to be rid of the snow mold.
I dropped it in a tree fern basket to reestablish over the next 6 weeks or so of the growing season and expect it to bloom in the spring!
Mealbybugs Hidden on Orchid Roots
Q. I just brought this orchid home and wanted to drop it in a clay pot when I saw all these mealybugs eating my orchid roots. What now?
A. Before you introduce a new plant to the growing area, apply a protective drench to kill any lurking pests. The Bayer imidacloprid product is a great systemic pesticide that can be introduced to the plant via the roots and absorbed throughout the plant.
It will kill scale, mealybugs, etc. from the inside out without your having to spray it. If you are lucky enough to find the imidacloprid product that is 1.47% strength, mix up 1 ounce of it in a gallon of water and thoroughly drench the growing media (at 0.74% strength, add 2 oz/gal; at 0.47% strength, add 3 oz/gal, etc.).
Bud Sheath Turning Brown
Q. The sheath on my cattleya is turning yellow and then brown, what should I do?
A. Whenever the flower sheath starts turning a sickly yellow or brown, it should be removed. Often there is condensation inside the sheath that will rot the emerging flower buds, particularly this time of year when there are large day night temperature changes. You should gently peel the sheath apart down to its base, and if it can be easily removed, peel it away from the pseudobulb. If it does not pull away easily, leave it alone so you don’t damage the emerging bud. It’ll pull off easily in another couple of days.
Wrinkly Leaves on Miltonia
Q. This miltonias looks like a mutant. What is wrong?
A. Your plant is telling you that it would like more water. The accordion-like pleating on the leaves will never go away, but the new leaves should emerge normally if you start watering a little more frequently.
Cymbidium devonianum Progeny
Q. These cymbidiums both have the species devonianum as one of the parents, why are they so different?
A. Our cymbidium expert Harry McElroy handles all cymbidium questions, he answers: The flower on the left is Cym. Devon Odyssey (devonianum crossed with erythrostylum) and the flower on the right is Cym. Vogelsang (devonianum crossed with insigne). The other parent of the plant on the left, the species erythrostylum, intensifies the devonianum lip as you can see in the flower while the insigne parent in the plant to the right breaks the color into spots. Unfortunately the erythrostylum cross would not be heat tolerant though the insigne cross would probably bloom in northeast Florida.
White Growths on Pots and Potting Media
Q. Sometimes when repotting I see a white growth on the pot or potting media, like this piece of large charcoal that was at the bottom of a clay pot for drainage. Stumped, I brought it to our go-to guy Dr. Courtney Hackney for answers
A. Through microscopic examination Courtney determined that the white growths are lichens. Lichens are a peculiar life form that is not a single organism, but rather a combination of two organisms, a fungus and an algae, which live together symbiotically. Usually lichens require light although fungi can extract energy from organic material and sustain both, but this is fairly unusual. Weird!
Water Soaked Leaves on Phalaenopsis
Q. Could you tell me if this is a bacterial infection of this phal?
A. That looks like bacterial soft rot, a very fast moving bacterial infection caused by Erwinia
that will kill the plant if it gets to the crown. Get a single edged razor and cut off all the soft, water soaked leaves an inch below the obvious infection. On your plant, that means cut the top leaves off at the base. Then drench what is left of the plant with hydrogen peroxide. Don't hesitate! Here's a link
for more information.
Catasetum Keikis on Pseudobulb
Q. My Ctsm. barbatum has 3 keikis on one of the pseudobulbs. They pop out and send their roots on a long journey down to the sphagnum. Should I cut the pseudobulb and lay it on sphagnum or just leave it alone?
A. Trust your instincts. Cut the pseudobulb and lay it partially immersed in sphagnum moss in another pot. Leave the rest of the plant alone in the pot except perhaps the yellowing pseudobulb should be removed too.
Bumps on Catasetum Leaves
Q. My catasetinae leaves developed bumps, some of them may have thrips or spider mites but I'm pretty sure this is not caused by an insect though my feeling is that it is transmitted from one plant to another nearby.
A. The catasetum has edema, which is a blistering on the leaf when the plant takes up water faster than it can transpire it. It happens if you water on a gray day or if you water late in the day and the night turns cool. It may look like it’s being transported from plant to plant because all your plants are watered at the same time and subjected to the same conditions. Here’s a link for more information.
Short Phalaenopsis Flower Spike
Q. My son found this strange flowering phal in our orchid growing area. The blooms are emerging from under the sphagnum moss with very little, if any, spike. What gives?
A. Every once in a while, a flower spike gets trapped and doesn't grow upward the way it normally would. This one looks like it got confused and punched a hole through the leaf and grew around and under the other leaves. If you follow the flower spike back to the base of the plant, you will see the circuitous route it took. It’s just an aberration that won’t repeat itself next year.
Rotting Pseuobulbs on Oncidiinae Plant
Q. I bought this Brassidium in May, keep it in bright light and am careful not to overwater. I just noticed soft and mushy rot in the center of the plant. Is it toast?
A. It’s not toast. Remove all the rot and discoloration with a sterile tool (sterilizing after each cut) and pour hydrogen peroxide on it (Banrot would be even better if you can find some).
After you cut up the plant, let it dry out a for a day or two by standing it in an empty clay pot. You probably won't have any roots, so you’ll end up putting it in sphagnum moss in a very small pot until roots grow. You may be able to repot it in regular mix by September or so and let it get reestablished this fall.
Brown Dots on Orchid Stem
Q. I have small brown dots on the flower stems of one of my three orchids that seem a bit sticky and resemble seeds. There are also a few on the back of some of the flowers. I can't find any legs, can you help me identify them?
A. That is scale. Remove the obvious infestation with either a Q tip or toothbrush dipped in some isopropyl alcohol and scrub the scale off the plant, the flowers, etc. You’ll have to repeat the treatment a few times. If you have some of the Bayer products containing imidacloprid, you can also mix some up and pour it through the potting mix for a more permanent fix.
Phalaenopsis Leaf Fell Off
Q. My orchid was doing fine until this morning. One of the leaves fell off and it was black at the end. What should I do?
A. That is Southern Blight or collar rot, caused by the fungus Sclerotium that has destroyed the heart of your plant from which new leaves grow. The center of your plant is dead though you still have two live leaves. If you kill the fungus so it doesn’t destroy those two leaves, it is possible that a new growth will emerge from adventitious tissue on the stem of the plant over the summer. You will have to cut away any discolored tissue in the heart with a sterile tool and then drench the heart with hydrogen peroxide. If you know anyone that has the specialty fungicide Cleary’s 3336 (repackaged as Thiomyl), apply it to the plant. Then, cross your fingers that a new plantlet will grow from the mother plant this summer. If the other two leaves die, you will have to replace the plant.
Phalaenopsis Leaves Yellowing
Q. I have a phal that still has blossoms on it, but the bottom leaves are turning orange, the whole leaf. Older leaves are thin and wrinkly. Is this a fungus?
A. Your new leaves look healthy, though they’re not as large as the older leaves which suggests the plant is not getting something it wants. It’s not unusual to lose a bottom leaf or two and gain a top leaf or two, though losing four bottom leaves is a lot. I don’t see any disease so I'm guessing it needs to be watered more frequently. When you water, water thoroughly until water runs out the bottom of the pot and then water some more. After that, water again when the mix approaches dryness.
Leathery Phal Leaves
Q. My phals have leathery looking leaves that are dark green and droopy. They are grown under grow light, doing well otherwise and blooming.
A. It looks like the phal is dehydrated, either because it needs to be watered more or the roots aren't absorbing moisture because the potting mix has started to deteriorate. When they’re done blooming, repot them into fresh mix. A trip outdoors for the summer time can do wonders for them if you have a covered or screened porch with an eastern exposure.
Flower Spike on Summer Blooming Phal
Q. I am repotting my phals and know to cut the inflorescence near its base, pretty typical for the normal hybrids. My question is what to do with the spikes on my summer blooming phals. These flattened spikes are shaped differently and some bloom off of an inflorescence that started last year. Do I cut these back or not?
A. That phal is one of the summer bloomers in the Polychilos subgenus that includes the species amboinensis, bastiani, cornu-cervi, fasciata, hieroglyphica, lueddemanniana, pulchra and violacea. The inflorescence should not be cut because it will continue to bloom on the same flower spike this and next season.
Snow Mold Growing in Degraded Mix
Q. I have some orchids that are very wobbly in their pots and when I looked at the roots, I found white masses growing on the roots and in the potting medium. What is it??
A. That is snow mold, a fungus that grows on the rotting potting media. It will eventually cover the roots suffocating them by depriving them of air and moisture. Remove all the decaying potting mix, drench the roots in physan or pool algaecide and repot in clean potting mix.
Q. I bought a pot of Maxillaria tenuifolia (coconut orchid) two weeks ago. I know I need to repot it very soon to have it re-establish and grow. But it just flowered and still has flowers on. Is it good to report it now?
A. For any orchid, the best time to repot is when the orchid is starting to grow new roots. When you see the new roots beginning to form, repot and the plant will reestablish itself the most quickly. Some information about this plant and pictures from the AOS website:
The long rhizome makes for a somewhat straggly plant that wants to climb out of a pot, but a good sized plant can be easily kept in a six inch pot. It will eventually start to droop over the edge as it grows up but by that time, you should plan to repot it anyway as it will take a couple of years to reach that stage by which time the media will need replacing. Basket culture is an optimal solution to accommodate this growth habit and a slab of tree fern will work equally well, although not offer as tidy a presentation. Most elements of Max. tenuifolia culture are quite forgiving with the main consideration being the avoidance of stale or soggy media. We have grown it in all sorts of media including osmunda, fir bark, coconut husk fiber or chunks and, of course, fir bark mixes. The paramount quality of the media is that it does not stay consistently wet so sphagnum may be the least suitable choice.
White Powder on Rl. digbyana Leaves
Q. The leaves on my B. digbyana are turning white. What did I do wrong?
A. Rl. digbyana grows and blooms best in the brightest of cattleya light. The white powdery substance on the leaves is a protective wax coating that protects the plant from sunburn. The white powder means that your plant is growing well!
Catasetum Never Entered Winter Rest Period
Q. My Ctsm. Penang never went dormant this winter. The prior year's foliage is shading the new growth which has two bloom spikes forming. Is this normal?
A. Many of the catasetinae enter their winter rest period in the late fall when their leaves yellow and fall off, during which time you water sparingly, if at all, and do not fertilize. Sometimes our plants don’t do what the books tell us they will do and you have to trust your instincts. As long as the mix is still fresh, leave the plant in the same pot and continue watering and fertilizing. It is possible it will rest briefly after flowering, like the species discolor and atratum, at which time you would limit watering and could repot. But if it insists on continuing to grow, I think it is telling you that it really likes your growing conditions!
Repotting Miniature Phalaenopsis
Q. From Spain, Stephen writes: I have acquired a couple of miniature phals that are in sphagnum moss. They seem to have filled their pots with roots, should they have bigger pots after flowering?
A. I love the multifloral phalaenopsis for their branching floriferous flower spikes. You can see the roots on the white phal are fat and happy. The purple phal looks like it has rebloomed in last year’s pot and the sphagnum looks degraded so the roots are probably damaged and somewhat rotted. When they’re done flowering, you can knock them out of the pot and assess the roots. You’ll choose your pot based on the root mass. Most likely they will go into 4 in pots but you’ll probably have to add more Styrofoam peanuts into the pot for the purple phal because of all the root loss.
Black Spotting on Cymbidium
Q. have some black spotting on a newly acquired Cymbidium, is it a bacterial infection?
A. The Cymbidium Man Harry McElroy writes: It could be Bacterial Black Spot, but it looks like the black spots I get on leaves when very cold or freezing water hits them. It could be that bacteria invaded the spot where freezing water dripped on the leaves. I would put the plant in a protected area and watch it for a while. Cymbidiums are less susceptible to this kind of spotting if they are given as much sun as they can take to harden the foliage. New leaves are very easily damaged by cold water droplets.
Fungicides and Bactericides for Orchids
Q. What is a reasonably priced systemic fungicide I can buy in small quantities? Can I use liquid copper as a fungicide bactericide and what is the dilution?
A. There are many nonsystemic fungicides. A reasonably priced fungicide is Daconil or pool algaecide/Physan and a reasonably priced bactericide is hydrogen peroxide.
Liquid copper and Kocide are reasonably priced and can be used as a bactericide and a fungicide, though you shouldn’t use any copper compounds on dendrobiums. Dithane or mancozeb is easily available but can plug your sprayer at the recommended concentrations.
For a systemic fungicide, Banrot is a good specialty product because it contains two chemicals, Thiophanate Methyl (sold as Cleary's 3336, repackaged in smaller quantities as Thiomyl) for Fungal Leaf Spots and Etridiazole for Black Rot, but it costs around $80 for 2 lb (I have seen 1 oz quantities advertised on Ebay for $10 but such repackaging may not be legal). There are more effective and expensive fungicdes, like Aliette.
The table linked at the top of the orchid diseases webpage
lists some of the various substances, what they are used for and what the dilution rate is. (Apr-13)
Q. Can you please identify the following orchids for me?
A. The yellow flowered orchid is an Oncidium alliance plant. The flowers look like Onc. ampliatum although the pseudobulbs don’t. The purple flowered orchid looks like a Miltassia (Mtssa.), which is an intergeneric cross between a miltonia and a brassia. I don’t know which cross it is, perhaps someone will recognize it and let us know. (Apr-13)
New Growths and Flower Spikes on Catasetum
Q. My Ctsm. tenebrosum has 6 new growths showing. Two of the new growths have 1 inch flower spikes forming from the base.
Is this the normal growth pattern, to have spikes forming with the new foliage? I have checked the flower spikes thoroughly and they are not secondary bulbs forming.
A. My friend Stephen Moffitt over in Houston tells me this is the normal growth pattern for this species catasetum (check out our catasetum website
). Ctsm. tenebrosum is the first to throw off new growth in the spring and tends to spike with the new growth. Hopefully you've already completed your annual spring repotting, otherwise it is probably best to repot next winter before new growth begins.
Leaf Shine Damages Foliage
Q. I just bought this orchid today and the seller said she had put leaf shine on it. I had to stop in a store on my way home and left the orchid in the car (I live in Florida) for about 30 min. I think the sun and warmth of the car made the shine soak in too much and now part of the leaves are turning brown and seem to be damp underneath!
A. You (or more correctly, the seller) should never put leaf shine on your
orchids because it blocks the stomata and the leaves can't breathe. During the
summer, you can easily sunburn plants by leaving them in the car. I don't think 30
minutes in the car during the winter should have had such a negative effect on them. I think
the leaf shine did them in and the seller owes you a refund.
photo by Colleen Pruett
Q. I bought a small Sedirea japonica a year ago. Over time, the root tips became dark brown.
It is in a small plastic pot the leaves look healthy. Recently I watered and misted
it more often, thinking that perhaps root browning is due to our dry, indoor
air in Canada. Any suggestions?
A. I think I'd repot it into a small clay pot with sphagnum
moss, keep it moist in the spring through fall time frame and let it get drier in
winter, fertilizing regularly during the growing season with dilute
Bud Blast on Phalaenopsis
Q. What can cause yellowing and dropping of buds? This Phal. amabalis has already dropped four buds.
A. Read Courtney Hackney's article
about Blooming and Bud Drop in Phalaenopsis.
Courtney writes that the hobbyist must remember that there are different breeding lines
among Phalaenopsis and they are not all equal when it comes to holding onto
their flowers. While there are some phalaenopsis that are relatively more cold tolerant, many phalaenopsis like minimum temperatures of no less than 60 F to 65 F. At lower temperatures, they may drop flowers.
Spots on Cattleya Leaves
Q. As shown on the photograph, the cattleya leaves are pale in color and twisted or spiral shaped. They the leaves are not 'right' beyond the spiral. In addition, the leaf appears mottled.
Do you have any recommendations?
A. It looks like there is scale about an inch above the pseudobulb. The scale will suck the juices from the plant and give it that mottled appearance. Look at the underside of the leaf and under the papery sheath on the pseudobulb and see if you see scale. A drench with one of the Bayer products containing imidacloprid will kill them. If you find the Bayer product containing 1.47% imidacloprid, add 1.5 tsp into a quart of water and pour it over and through the mix to thoroughly drench the potting mix. The orchid will absorb the imadacloprid through the roots into the leaves and kill the scale from the inside out.
Can Dendrobium Be Revived
Q. I purchased a very nice Dendrobium amethystoglossum at the 2012 JOS Orchid Show. After the blossoms fell, I repotted it into Aliflor and dutifully placed it outside under "the orchid tree". All was well until the May monsoons, after which the orchid appeared to have died; by August, in spite of moving it to a drier location, all leaves had fallen off and the roots were all dead. Rather than throw away the "skeleton", I placed it in a pot with other dead orchids and left it in the greenhouse because the canes still had a slight bit of green.
Seven months or so later, I've got buds appearing on canes that only have dead roots. I'd love to think I could resurrect this orchid, but what is the best method?
A. Dendrobiums are very hardy critters. That plant has lots of flower buds, although it seems a tad early for it to bloom. The roots still look viable to me. I think I’d pot it back up in a small pot in a coarse mixture and see what happens. You may elect to abort the flowers to encourage the plant to grow vegetatively rather than waste its energy on blooms, though it may also be the plant’s last act of defiance in which case you should enjoy the blooms. Pot it up and give it a fighting chance. It’ll do what it’s going to do!
Bud Blast on Phalaenopsis
Q. About 6 weeks ago, I bought a few orchid plants and two alternate buds dropped on my white phal.
A. If you've just brought an orchid home, the most likely reason for bud blast is the damage to the sensitive bud from its being moved or radical changes in the amount of light and water the plant is used to. It can also be caused by watering: too dry and the moisture can be drawn from the sensitive buds or too much water can cause root rot and the plant can't sustain the emerging flower. Radical temperature changes can also cause it: drafts from an air conditioner or heater can cause bud drop and condensation from day night temperature changes can cause buds in the sheath to rot. Chemicals from fumes and ethylene from combustion engines can cause the buds to age and distort flowers. Insects like aphids and thrips can feed on the buds and cause them to drop or be deformed after opening. Other reasons include drying out from too low of humidity or being too close to grow lights and chemical damage from fertilizers. Sometimes bud blast occurs and there is no obvious reason for it.
White Fuzz on Phalaenopsis Orchid
Q. I was wondering if you could kindly have a look at the pictures of the upper and lower leaf surfaces of my orchid and give me your verdict on what is wrong.
A. That looks a whole lot like mealybugs. Get some Q tips and isopropyl alcohol and start wiping away the white fuzz. The pests will hide in all the plant crevices, such as between the leaves at the base of the plant and below the surface of the potting medium. A drench with one of the Bayer products containing imidacloprid will kill them. If you find the Bayer product containing 1.47% imidacloprid, add 1.5 tsp into a quart of water and pour it over and through the mix to thoroughly drench the sphagnum moss. The orchid will absorb the imadacloprid through the roots into the leaves and kill the mealybugs from the inside out.
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.