New orchids arrived with black spot - ?

[edenmackay]

Hello--so glad to have found this forum!

I just ordered 3 orchid plants from a nursery across the state (I live in Tampa, FL) and they came with small amounts of black spot (bacterial infection) that seems to be spreading. I have 2 books which both recommend fungicide (which if it's bacterial rather than fungal makes me confused?) but neither says exactly what.

I have had some bad experiences with plant sprays in the past, so I'm leery of doing something stupid. What would you all recommend I treat them with?

Also, this is probably a stupid question, but none of my other 20+ plants have this. Can it spread to them? Do I need to keep these orchids away from my others?

Thank you in advance for your advice!
Eden Mackay

[Cynthia, Prescott, AZ]

If it is truely spreading (rots usually spread very rapidly), the best approach is to cut away the rot, with a margin of healthy tissue, a half inch if you can work it out. I would contact the seller if you just received them and explain what is going on. He may give you recommendations, and my take on the responsibility of their survival. Some good dealers will replace such plants. Keep the plant away from the others for just a bit, since you are going to remove the diseased tissue, and particularly, keep the trimmings far away. Use a little sulfur dust or cinnamon on the cut surfaces. If the rot does not start up again, you can end the isolation. Some times the surgery leaves very little of the plant, but if it is spreading, you have no choice.

If it seems to be spreading so slowly you are not sure it is actually spreading, then you may want to wait on the surgery. Some times problems are self limiting. I have never had much luck with sprays, and in particular, would not depend on them as a first line of attack for something spreading rapidly. The best, or so I have heard, is Phyton 27, systemic and works on both fungal and bacteriologic activity. However, I never recommend this as the stuff is ungodly expensive. I paid $53 for an 8 oz bottle, and haven't really seen a lot of good results. Cynthia, Prescott, AZ

[edenmackay]

Thanks, Cynthia.

I do think it's spreading, as I recall seeing only a couple of small spots and now I have whole leaves turning dark. We've had a lot of rain here, so maybe they are just staying too damp? I don't really understand though why my other orchids would not be affected by the same amount of rainfall (these are similar species to what I already have), unless they already were affected prior to shipping.

I may have to contact the seller but feel bad as it's my first order with them. I hope I don't have to.

I did cut away the most affected leaves--one very bad leaf per plant, pretty much. Pretty much every leaf has a tiny dot or two, I couldn't really cut them all off, or does that mean cut out just the affected part of the leaf?

Thanks for the info on the Phyton, that does sound a little exorbitant, so I will watch and see before I get that drastic.

I'm mostly just terrified that my existing plants will get this, they are all very healthy now and I have separated them but they were next to one another for probably about a week.

Thanks again for your input!

[Cynthia, Prescott, AZ]

The small spots are probably something else. The usual problem when plants are not dry when the temp starts to fall, or if the plants are grown too cool (or even too hot). Your new plants are probably under stress from the change in environment. Stress is the biggest cause of rot and fungal problems. Healthy plants don't get these problems. A change in the growing conditions can make a previously healthy plant into a very susceptable plant. So try to keep these guys going until they get used to your environment, and watch for any change in the spots. Cynthia

I don't know why you're hesitating to contact the seller. If you had walked into a new department store and bought a blouse and when you got home you found stains all over the back, would you hesitate to take it back? Sellers should sell good merchandise, whether you're a new customer or not.

[jerrymeola]

Bacterial rot is rampant throughout Florida just now with the heavy rains. It is mostly on cattleyas. Dens and oncidiums do not seem to have the same blackening leaves. It is always a summer problem here in commercial greenhouses but this year is much worst because we have had a lot of cloudy days. Last year there was enough sun to dry the plants between heavy rains this year they are not drying.

Once bacterial rot starts it is hard to get under control. I have had to destroy 150 plants (out of about 800) in one shade house. I am not selling anything out of that shade house until at least a month with no new cases around the the end of the summer probably.

The growth rate is extremely fast with whole leaves looking good one day and black the next.

Rot is spread by touching and the close packed growing tables of commercial house like mine add to the problem. Be very careful handling them and do not use the knife or scissors on healthy plants. I would quarantine the plants or destroy them.

In general the pseudo bulb also rots fast and cutting the leaf is not enough unless you get it very soon.

Physon 27 is a good product to prevent the problem but does not work as a cure. Nothing seems to cure. Early spots can be rubbed with peroxide if you are not sure if it is sick since peroxide will not do any harm to a healthy plant. Physon 27 needs to be applied at least weekly during this time of year in a commercial house. I was out of town when mine started and I am paying for it now.

Contact the seller. Rot spreads so fast they may have looked good when he shipped them. If you wait too long he may claim the problem occurred in your home.

I will try to get a group of photos to explain the problem and its stages and post them later. I destroy the plants so fast that I only think of photos after they are gone.