Guignardia advice?

[MDBuch]

So I’m having what appears to be Guignardia spreading among an indoor population. The only difference is that the leaves aren’t just getting spots that spread. They’re getting the brown spots, but also some are getting global yellowing of the leaf as well as some small spots.

My question is what is the quickest way to help? I cannot get my hands on a fungicide for a few days. Would a 10/1 alcohol misting help as well as increasing air circulation? Are there any other “home remedies” that could help until I can get daconil or 3336?

Does this appear to be Guignardia?! Help!

Thanks!

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[katrina]

I'm not sure your issue is fungal but the easiest thing to do would be to remove the affected areas. Cut behind the discoloration and into green tissue.

The one thing that jumps out at me is how dark your leaves are. They should be a lighter green and I suspect you aren't giving your plants enough light. Where are you growing them? Windows? If so, what direction/exposure are they located?

[Ray]

Whatever the infection may be, any topical spray is of little-, to no value; you need something systemic.

At the risk of seeming self-serving, you might want to consider Inocucor Garden Solution. It is a biological product made up of living consortia of beneficial bacteria and fungi that predate pathogenic ones. It is sold as a preventive, but can cure such infections, as well.

[MDBuch]

Katrina, they’re growing about four feet from a west-facing window.

Would that mean I’d need to cut this off wherever I’m seeing it? I’ve got eight plants by this window, and I’ve found small patches of it on a significant portion of the plants, probably around 40% of the leaves there have some kind of spotting. Not nearly as bad as those pictured, just a few spots, but they’re there nonetheless.

---------- Post added at 05:37 AM ---------- Previous post was at 05:30 AM ----------

Thanks Ray. Are there smaller quantities available? Should I just go through the Southern California rep? Is it only available for online order, or can I find it in any local nurseries?

[Ray]

Originally Posted by MDBuch

Thanks Ray. Are there smaller quantities available? Should I just go through the Southern California rep? Is it only available for online order, or can I find it in any local nurseries?

One liter is the only retail size available, and I am not aware of it being available in nurseries. Their big markets are large-scale horticultural operations.

I sell through Amazon, but I pay the shipping cost of you order it directly from me.

[Roberta]

Just a thought... We just came off a serious hot spell. Is it possible that you're seeing delayed reaction to excess heat on those leaves? I am almost a neighbor... and I have seen signs of heat damage (some showing up only now, a week later) on my plants in places I would not have expected... they weren't getting all that much more sun during the heat wave, but they clearly got HOT and the low humidity sure didn't help.

I agree with Katrina that light is probably inadequate... Phals don't need, or want, direct light but they need significant duration... When i was growing them in the house, I found that I needed to give them supplemental light (cheap Home Depot fluorescents, now LEDs would probably be better) about 12 hours a day... light coming in the window was good for maybe 4 hours a day and that was not enough.

[Orchid Whisperer]

I agree with GRADUALLY increasing light. If dark patches are getting larger, cut off into green tissue. If the dark patches are not growing, there may be no reason to cut.

---------- Post added at 04:29 PM ---------- Previous post was at 04:17 PM ----------

I agree with GRADUALLY increasing light. If dark patches are getting larger, cut off into green tissue. If the dark patches are not growing, there may be no reason to cut.

[MDBuch]

It’s difficult to say regarding the heat issue as these are all growing indoors and we’ve got air conditioning.

I’ll have to see what I can do to move/add light.
I might think about moving them outside. I have a couple areas I can move them and get a shade cloth going. Just a shame not having them by my desk!😫

---------- Post added at 06:58 PM ---------- Previous post was at 06:57 PM ----------

Roberta, do you have any outside? Do they do okay with the coldest parts of winter here(I know it’s usually no lower than low 40s)? I read often that most plants don’t like getting lower than maybe the high 40s?!

[Roberta]

Originally Posted by MDBuch

It’s difficult to say regarding the heat issue as these are all growing indoors and we’ve got air conditioning.

I’ll have to see what I can do to move/add light.
I might think about moving them outside. I have a couple areas I can move them and get a shade cloth going. Just a shame not having them by my desk!😫

Not Phalaenopsis... getting much too cold to have them outside (they hate less than 60 deg F) In the spring/summer you an get away with it but not now. In fact I would not move anything that has been inside to the outside this time of year, even if it is a type that could grow cooler... orchids need time to acclimate. Spring is best for that.

I'd suggest just keeping an eye on these plants. if it gets worse you may need to cut away bad parts, repot if necessary but again not the ideal time of year.

As for heat... all you need is a blast of sun for a few minutes... you'd be surprised. It's the surface temperature of the leaf, not the ambient temperature in the room. And if you don't catch it in the act, it may be very non-obvious. (Had that experience... puzzled for a very long time before I just happened to be in the right place at the right time to see the sun hit a plant unfiltered for only a very few minutes.)

I grow most of my orchids outside... but select them for cold-tolerance. Marginal ones acquired in the fall and winter stay in until spring. The few warm-growers that I just had to have now have a small greenhouse,( in my last residence they got the spare bedroom) Check out my website Roberta's Orchids and look at the Index of Plants page to see what I grow outside and what I don't.

[MDBuch]

Thanks Roberta! Well, I’ll definitely have to get a large mounting of two phals on a big branch inside before it gets any colder!