Brown Sunken Spots on Orchid
Q. I was looking at your excellent site and saw the Q&A. Attached are two photos of a disease or pest I have on an orchid, along with another picture showing it during happier days. Any assistance you could give diagnosing it and advising on treatment would be greatly appreciated!
A. That looks like a beautiful Den. aggregatum. It looks like it has bacterial brown spot, an advanced case on the lower leaf with the advancing yellow margin, and a younger infection on the upper leaves where there are sunken brown spots. To stop the spread of disease, cut away the severely damaged leaves with a sterile razor blade and then pour full strength hydrogen peroxide over the rest of the plant. It's possible the plant got too cold or there was not enough air movement, so the infection set in. Now that it's spring, it should start to grow and grow new pseudobulbs, so it will recover by the end of the summer. (Apr-12)

White Deposits on Orchid Roots
Q. This orchid has flowered wonderfully but now has this white deposit on the roots. I think it is a good time to repot it, there are only two flowers left on the stem. Should I treat the plant with chemicals too, and if so what?
A. Mealybugs have been feasting on your roots. Use a water jet to remove all the sphagnum moss from the roots as well as any white masses. Then spray the plant, top to bottom with an insecticide for mealybugs (one containing imidacloprid would be great). Here's a good article on mealybugs. (Apr-12)

How to Grow a Gift Orchid
Q. A friend gave me 3 orchid plants just before Thanksgiving. They were doing fine until about a week ago and then they started wilting. All the flowers are off and I know that orchids do come back. What sort of care do they need to rebloom and when might they bloom again?
A. You have phalaenopsis orchids. They bloom for about 3 months each year. After blooming, you'll cut the bloom spike at the base of the plant and repot them into fresh mix. Then find a nice shaded place under cover outside for them to grow in the summer. Water and fertilize them regularly. You'll leave them outside for the first cold snap around Halloween, the cold weather will tell your plant it's time to start initiating the flower spike. Then move them inside to an eastern or south facing window for the cold weather. You'll see spikes by Xmas and the flowers should be open by Valentine's Day. (Apr-12)

Elongated Discoloration on Cattleya Leaf
Q. I have large areas of discoloration on my cattleya. What is the problem?
A. That is bacterial brown spot (caused by Pseudomonas or Acidovorax). On the upper side of the leaf, you see an elongated reddish discoloration. The sunken bacterial spots have coalesced and are clearly visible on the underside of the leaf. That infection is fairly extensive, so cut off the affected leaves to at least an inch below the discoloration and pour some hydrogen peroxide over the rest of the plant. Spraying with a copper fungicide / bactericide would be even more effective. (Apr-12)

Brown Nodules on Orchid
Q. I came across your very informative webpage. Attached is a picture of one of my orchids with small brown modules on it. They are easily removed. Seems too big for mites?
A. That is hard scale, you can remove it with a Q-tip and isopropyl alcohol or you can put a sprayer in the alcohol bottle and spray the whole plant. Here is a more information. (Mar-12)

Flower Spike in Middle of Phalaenopsis Crown
Q. My phalaenopsis has a flower spike coming out of the center of the plant rather than at the base of the leaves. Is there something wrong?
A. Your plant will probably cease to grow new leaves from the apical crown of the plant after this spike is finished. Some people believe this atypical flowering is from too much light or usage of systemic insecticides. A plant that does not resume normal growth will usually throw one or more new plants or keikis from the base of the plant, so don't throw it away. Until it does produce new plants, continue to treat it in a normal manner. (Mar-12)

Transparent Spots on Phalaenopsis Orchid
Q. Some of my phalaenopsis have developed spots. They’re transparent from the bottom and raised on the top. I haven’t seen any crawlies, fuzzies or webs. There is a small pinhead in the center of each blight. This has developed only over the last four/five days or so. Can you help?
A. I'm pretty sure it's edema which is caused by the plant absorbing more water than it needs or can transpire. This typically happens during cooler weather when the water demands are lower and you water late in the day or on a gray day. The leaf will just have that blister on it until it drops of natural causes. (Mar-12)

Bud Blast on Phalaenopsis Orchid
Q. I have a small phalaenopsis that has bloomed for a couple of years. I just got two new spikes with buds on them and then they got droplets of sap on them and are now withering. The ends of both spikes and the buds look like they are going to die. Can they be salvaged or should I just cut them off?
A. The otherwise healthy flower spike looks like it rotted right below the flower buds. The bottom and top of the spikes both look healthy, it looks almost like someone squeezed the life out of the middle of them. It’s possible that a sucking insect like a mealybug or thrip caused the bud blast and the plant sap is left from their activity. It’s also possible a fungus like fusarium caused the rot. At this point, I'd cut the spike at the base of the plant, repot it in fresh mix and get it reestablished so it'll grow over the summer and flower during the next bloom cycle. It's a shame, and a double spike too! (Mar-12)

Cattleyas Outgrowing Their Baskets
Q. I have two nodosas, one in a 5" basket and the other in a 3" plastic basket. Both are overgrown in their present containers and pretty heavily budded. I might just put the smaller one in a larger plastic basket without any trimming, just another layer of media (love that wine). The larger one looks impossible to dismantle without serious damage. What to do?
A. Just drop them both in larger baskets. You can get plain wire baskets and drop them in, basket and all. If you want, you can line the basket with screening mnaterial, plastic fencing material or shadecloth to hold some potting media between the two baskets. Don't disrupt the roots, they look way too happy just the way they are! (Feb-12)

Sunken Brown Spots on Phalaenopsis Orchids
Q. I'm seeing lesions on the leaves of some phalaenopsis that look like black rot. I'm in a panic given all 6 of my plants are in spike. Will fungicides damage the plant while in spike?
A. That is bacterial brown spot, the large spot is an advanced case and the smaller spots are new infections. Pour some hydrogen peroxide on the sunken spots. If they don't enlarge, you will have killed the active bacteria. If they do enlarge, you may have to cut away the damaged tissue. The hydrogen peroxide will not harm your flower spikes. This disease is a major bacterial problem affecting phalaenopsis, here is a link for more information. (Feb-12)

Dendrobium anceps
Q. Do you know the name of this orchid? This is its first bloom for me.
A. That is Dendrobium anceps. Grow it with your cattleyas. (Feb-12)

Cold Damage from Proximity to Window
Q. What is the translucent spot on my dendrobium plant? I moved the plant away from the window to a cooler room.
A. It looks like the discoloration is on the upper, younger, more tender leaves that would be the first affected by cold. If it is cold exposure and the leaves are water soaked, it's possible that some sort of secondary rot may form. If it does, cut the leaf about an inch below the discoloration and pour hydrogen peroxide on the remaining leaf parts. The good news is the dendrobiums are very hardy orchids and will recover quickly. (Feb-12)

Cattleyas Outgrowing Their Baskets
Q. I have two nodosas, one in a 5" basket and the other in a 3" plastic basket. Both are overgrown in their present containers and pretty heavily budded. I might just put the smaller one in a larger plastic basket without any trimming, just another layer of media (love that wine). The larger one looks impossible to dismantle without serious damage. What to do?
A. Just drop them both in larger baskets. You can get plain wire baskets and drop them in, basket and all. If you want, you can line the basket with screening mnaterial, plastic fencing material or shadecloth to hold some potting media between the two baskets. Don't disrupt the roots, they look way too happy just the way they are! (Feb-12)

Sunken Brown Spots on Phalaenopsis Orchids
Q. I'm seeing lesions on the leaves of some phalaenopsis that look like black rot. I'm in a panic given all 6 of my plants are in spike. Will fungicides damage the plant while in spike?
A. That is bacterial brown spot, the large spot is an advanced case and the smaller spots are new infections. Pour some hydrogen peroxide on the sunken spots. If they don't enlarge, you will have killed the active bacteria. If they do enlarge, you may have to cut away the damaged tissue. The hydrogen peroxide will not harm your flower spikes. This disease is a major bacterial problem affecting phalaenopsis, here is a link for more information. (Feb-12)

Dendrobium anceps
Q. Do you know the name of this orchid? This is its first bloom for me.
A. That is Dendrobium anceps. Grow it with your cattleyas. (Feb-12)

Cold Damage from Proximity to Window
Q. What is the translucent spot on my dendrobium plant? I moved the plant away from the window to a cooler room.
A. It looks like the discoloration is on the upper, younger, more tender leaves that would be the first affected by cold. If it is cold exposure and the leaves are water soaked, it's possible that some sort of secondary rot may form. If it does, cut the leaf about an inch below the discoloration and pour hydrogen peroxide on the remaining leaf parts. The good news is the dendrobiums are very hardy orchids and will recover quickly. (Feb-12)

Dendrobium Leaves Yellowing
Q. My dendrobium had seven spikes blooming under a tree this fall. Now all the leaves are yellowing and dropping, why?
A. Many dendrobiums are tolerant of the cold, but not the phalaenopsis type. They don't enjoy temperatures below 55 or 60. If they get colder than that, the leaves will yellow and drop. The good news is that the plant will perk up again in the spring. (Jan-12)

Salt Encrustation on Clay Pots
Q. I bought a lot of used orchid pots and have not been able to remove the salt encrustation, how can I remove the white lime scale from the pots?
A. All pots should be soaked in soapy water and scrubbed to remove roots, potting mix and other detritus and then disinfected by an overnight soak in a mix of bleach (10% bleach or 9 parts water to 1 part bleach) and pool algaecide (2 tsp/gal if 10% strength) followed by a second soak to dissolve the chemicals. An hour bake in the oven at 225 degrees will kill any virus.
- Dishwasher. If the pots still have visible white stains, run them through the dishwasher with twice the normal amount of soap. The heat and soap will draw the salts either out of the pot or to the outside edge of the pot. Try scrubbing any residual salt from the pot.
- Mild Acid Soak. If the pots still have visible white stains, try an overnight soaking in a mild acid. Use white vinegar in whatever concentration you are comfortable handling, either a pure or a diluted (10%, 25% or 50% vinegar) solution. Scrub any residual salt from the pot followed by a second soak to dissolve the acetic acid.
- Nuclear Option. If salt encrustation is still present, consider admitting defeat and replacing the pot because the next alternative is the nuclear option. It involves a concentrated acid soak using muriatic acid, either pure or diluted (10%, 25% or 50% muriatic acid) followed by a fresh water soak to remove the acid from the pot. There are many safety and environmental hazards involved with handling muriatic acid, so be prepared to follow all label precautions, use gloves, goggles, etc. as well as have a disposal plan because the acid is highly corrosive and foams excessively when you try to neutralize it with limestone prior to disposal. Muriatic acid represents a potential threat to you, your pets and your environment that can be avoided by simply replacing the pot. (Jan-12)

Lower Phal Leaves Yellow and Drop
Q. Some of the lower leaves of my phals are yellowing. I know this happens often right after repotting, but these phals were reestablished, so what’s happening?
A. I think that is Collar Rot, or Southern Blight, caused by the fungus Sclerotium. In phals, the base of stem turns light yellow, later dark brown, and the infection spreads to roots and leaves. White fungal growth can sometimes be seen on stems. There is a rapid collapse and rotting of the plant. Isolate it from your other plants, spray the surrounding area and plants with pool algaecide and drench the infected plant with a thiophanate methyl solution (Cleary’s 3336 or Banrot). (Jan-12)

Mealybugs on Paphiopedilum Flower
Q. I have mealybugs on some just in flower paphs. They are all over the flower. (a friend gave me spray with alcohol, water and soap but told me not to spray the flower). Now what?
A. Use a Q-tip dipped in alcohol to delicately kill the mealybugs on the paph flower, and then your friend's concoction can be sprayed on the flower stalk and in all the paph crevices. They must be in between the leaf fans at the base of the plant and crawling up to dine on the delicous flowers, so really spray in between the leaves and in fact drench a little in the mix cause they can hide there too. (Jan-12)

Dendrobium spectabile
Q. I am trying to cope with this huge Den. spectabile. It was repotted last year and though it didn't seem to send out any new roots, it has 5 new shoots on it and I am wondering if I can cut off some of the old canes that look awful. I had it outside most of the summer and the old leaves have brown spots and edges on them (no bugs that I can see) and the new leaves are fine. Will it hurt the plant to cut off some of the old canes? The buds where the blossoms grow out seem to be old and dried up. Any advice?
A. If the leaves look diseased, you can cut them off, but leave the canes as this is where the plant stores energy and water (think of them as humps on a camel). You can remove the canes if they are soft or withered, otherwise leave them on, particularly because this dendrobium will bloom from old as well as new growth. The Den. spectabile blooms in the March time frame. If you've got 5 new leads it should be healthy and happy. Be patient, give it a ton of light and plenty of water and keep your fingers crossed! (Jan-12)