Dealing with Bacterial diseases

[Lars.Kurth]

Over the past few years, I have been very careful in my greenhouse to avoid any fungal diseases in the winter period. Here in the UK, short and grey winter days are a real problem and I hardly get any sun in winter. This makes plants really susceptible to fungal diseases. As a consequence I have been following a prophylactic regime of fungicide treatment, and as a result I had little problems.

However just a few weeks ago I got an outbreak first of bacterial leafspot and now of bacterial softrot. I mistook the leafspot initially for a fungal leaf spot, but I was obviously mistaken.

To treat I have started to add Physan 20 to the water reservoir to ensure that a) the source of the issue is not the water, b) ensure that I don't spread the issue during watering. I have sprayed the plants that showed signs of bactrial leaf spot with a copper based fungicide which seems to have helped prevent the spread so so far. I also have destroyed plants that showed signs of softrot (about 10 so far).

Now reading up on the issue: it appears that there is not much more I can do. Except maybe getting Phyton 27. Does anybody have any experience and advice for me? First of all with the current outbreak.

The weather this year has also not been helping: we have had a relatively warm autumn and winter so far. As a result, the greenhouse heating is not kicking in as much as one would expect at this time of year and thus humidity in the greenhouse is higher than normal. Plants dry out less quickly (I have been watering less)

[cdayinflorida]

Lars, I would hit it hard with a combo of systemics. I use Dithane M-45 and Thiomyl about a tsp per gallon. The next time I spray I use BanRot and Thiomyl same ratio. I spray every 10 days and bump that up to every week during the winter month (January) and when we are in the height of our rainy season.

I have great success with Vandas this way.

[cdayinflorida]

I would add that I use peroxide after I cut out the infected parts and then wipe on neosporin.

[Brutal_Dreamer]

I would add that I use peroxide after I cut out the infected parts and then wipe on neosporin.

I can only add to Cathy's advice that after cutting away tissue on infected plants, instead of peroxide and neosporin, we fill the cut edge with a sulfur powder. (like used to stop bleeding when cutting animal toe nails - sorry, cannot think of the product name).

cheers,
BD

[Naoki]

I do not mean to de-rail the thread, but I had to share this.

Bruce, Mike even put that stuff on his bleeding issue.
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[Cjcorner]

I recently had a plant develop a round brown spot, in spite of my spraying as well. I put a blot of cinnamon directly on the spot and it has dried out and is no longer a problem.

[Lars.Kurth]

Lars, I would hit it hard with a combo of systemics. I use Dithane M-45 and Thiomyl about a tsp per gallon. The next time I spray I use BanRot and Thiomyl same ratio.

None of these are actually effective on bacterial orchid diseases, but work for fungal diseases.

I can only add to Cathy's advice that after cutting away tissue on infected plants, instead of peroxide and neosporin, we fill the cut edge with a sulfur powder.

Sulfur powder does work for sealing wounds, as well as cinnamon. I would probably do this if I had the space to isolate affected plants, but I don't.

[opaline]

bacterial rot problems have been a real pain for me too lately, not so much in the length of time collecting and growing but during the last 8-10 weeks. A real difficult problem. The losses have been overwhelming not to mention catching a new delivery with a problem itself. Have used systemic fungicides but to me if its taken hold then theres not much one can do rather alter conditions and control situ until a solution has arisen.???????? I would say 50% of the collection has been killed. Its a very speedy and secret killer. Certainly something that has had me think about orchids as a speciality. Too much heartache!

[Lars.Kurth]

I think the weather at the moment does not help: too warm and I would not be surprised if many bacteria make it from outside into the greenhouse. With temperatures between 8-15C the heating does not kick in often enough which helps create conditions that make it easy for bacteria to multiply.

I did find that "Bayer Rose & Ornamental Spray Garden Insecticide Fungicide" has helped stop the spread a little, but some orchids really don't like this stuff. Dendrobiums drop leaves, so do some Aerangis a day after application. So this can't really be used in a preventative matter. I am hoping that Python 27 helps (I am going to the US next week and will bring a bottle back).

This is partly my fault: I started getting some leaf spots in October and didn't take them that seriously. I just thought my fungicide regime would deal with it. Many of the plants which got leaf spot, then developed soft rot (probably creating an opportunity to infect). As a result the disease got a few weeks headstart.

My problem is that I can't change my conditions much. My greenhouse is too full and it is almost impossible to ensure that water droplets don't make it to other plants. At least I know now what to look for next year.

[opaline]

I think the weather at the moment does not help: too warm and I would not be surprised if many bacteria make it from outside into the greenhouse. With temperatures between 8-15C the heating does not kick in often enough which helps create conditions that make it easy for bacteria to multiply.

I did find that "Bayer Rose & Ornamental Spray Garden Insecticide Fungicide" has helped stop the spread a little, but some orchids really don't like this stuff. Dendrobiums drop leaves, so do some Aerangis a day after application. So this can't really be used in a preventative matter. I am hoping that Python 27 helps (I am going to the US next week and will bring a bottle back).

This is partly my fault: I started getting some leaf spots in October and didn't take them that seriously. I just thought my fungicide regime would deal with it. Many of the plants which got leaf spot, then developed soft rot (probably creating an opportunity to infect). As a result the disease got a few weeks headstart.

My problem is that I can't change my conditions much. My greenhouse is too full and it is almost impossible to ensure that water droplets don't make it to other plants. At least I know now what to look for next year.

Ditto Lars! have also been using bayer fungicide systemic. Very difficult to intervene when its to complicated stopping water splashing/ dripping from plant to plant. My grow room (inhouse) is consistently 16oc - 18oc minimum 24 - 28 oc day max with most mounted/ hanging/ suspended.

I too think that I did not take the infection mystery that hit my stanhopea collection autumn time and its metamorphasized or dominoed from there but cant be too sure. Certainly cross infection or poor quarantine at a time when it was pratically party time for bad pathogens. On the Stans leaves I had yellow/ brown spots develop on foliage and pretty much isolated and then rapidly radiated outwards killing leaves. After a short period soft rot escalated and my grow room is well aerated so its my spraying that was the key. Bulbs rotted and stunk grotesquely and so on and so on with leaves stems etc etc.

The victims started to syphon off with less death rate but still after half my prided tropical/ exotic/ epiphytes was killed. Noticed another ( brassia) in last 24 - 48 hrs.

My problem lyes now with the phytotoxicity effects of using excess chemicals. At this point I can live with the losses but strongly debate any further future investments as the obstacles increase in severity from a dry/ reasonably warm enviro attracting spidermite to a moist cooler situ resulting in this. Abit of a shame for a great hobby that has been a great experience but seems a lose lose/ catch 22 situation. The fungicides and all the other *!?^%cides will hopefully stabilize current situation but will now have to watch as my heliconias, nepenthes, epiphyllums and remaining orchids' leaves dry up, crisp and die!

Its a complicated one for sure and sorry for moaning on your thread. lol