Ailing orchids

[Rudy]

I am about to ditch some orchids that are obviously very sick and I am afraid they will spread disease to my remaining orchids.
The first one is a phalaenopsis celebensis.
I had three healthy looking leaves until a couple of months ago.
I cut away one leaf about a month ago and sprayed the remaining two with fungicide and some insecticide against mites. Now there is another leaf ready to go into the dustbin.
One remaining healthy looking leaf left. For how long?
Anyone who could tell me what is going on?

And this dendrochilum panganiense doesn't look too healthy either.
I have been cutting away a few leaves or parts of leaves.
The brown spots keep spreading.
I guess this one is ready for the compost pile as well, not?

[catttan]

I think your plants are suffering from sunburn followed by attack of fungus.The phal leaves being more succulent are more susceptible to the fungus or bacteria attack. The dendrochilum,having tougher leaves, I am sure will recover. Sometimes a sudden exposure to strong sunlight will result in burning of the leaves; ditto with strong concentration of insecticide. The resultant injury may give rise to infection from bacteria and fungus. In such cases cut down on watering and treat infected part with fungicide or cinnamon powder.Physan, if available., is the best treatment.

To prevent mite infestation give plenty of ventilation and wet the underside of the leaves when watering, particularly of phals, paphs and dendrobiums.

[Rudy]

Sunburn seems rather unlikely. We're in mid winter and the weather has been very drab and grey out as of late. Moreover my orchids are behind darkened glass (not my choice...) and I have trouble growing orchids that need lots of light, such as cattleya's.
Fungus or bacteria attack is very much possible and maybe an overdose of insecticide is precisely the cause for the weakening of the phalaenopsis. Since I did not know what was causing the blotches I treated the plant both with insecticide and fungicide and maybe I overdid it a bit.
With regard to the dendrochilum, I am still puzzled on what to do. I didn't treat it with any insectide. And if I keep cutting away the infected leaves the way I have been doing for the last few weeks, soon there won't be any left.

[Brutal_Dreamer]

Try increasing air movement around your plants. It may be a fungus caused by staying too wet (dendrochilum). Good luck to you, Rudy.

Cheers,
BD

[Gin]

Hi , Have the plants had a mite attack ? if so fungus will set in on the damaged leaves ..

[Rudy]

I'm not sure. I didn't see the mites myself (I gather it's hard to see them anyway), but some of the spots on leaves of other Phalaensopsis on my windowsill made me think I might have mites.

[ang709]

Try rubbing a tissue on the bottom of the leaves. If you see red streaks, it is mites.

[remo]

I hope you have segregated the affected plants. I would also pretreat any other plants that may have come into contact with the infected ones with fungicide/miticide and like Bruce suggested keep the air moving around them. Best of luck.
Remo

[Rudy]

I have indeed segregated the affected plants.
What would be a good miticide? I sprayed them with Axoris Quick Spray ( a commercial brand containing thiamethoxam and abamectine) even though I read later on that this product shld preferably not be used on orchids....
As fungicide I used Sporgon (Physan and Cosan etc. are not being sold out here).

[ang709]

I have Safer's Trounce with success as a miticide. It combines pyrethrins and insecticidal soap. I don't know if it's available in your area though...