Fungus or Virus?

[wisechild9]

I was given some orchids as housewarming presents a couple of years ago. They are all phalaenopsis and have done well. But in the past 6 months, they've all had white patches show up on their leaves and their leaves look grainy with them. I thought maybe they were just getting dry (low humidity) so I was water spraying them. Now I am wondering, are these scales? In the last month, I am also now seeing the tips of leaves turning yellow to brown to black. So I am thinking there is definitely something wrong. The photos are at photos.yahoo.com/wisechild9


Just today I have dusted 3 of them with cinnamon to see if that will change anything. Please help!

[Cynthia, Prescott, AZ]

Does the underside of the leaf look worse than the top? My first guess is mite damage. Mites are chlorophyll eaters, and often leave a sivery look. If it is mites, and you would probably need a microscope to know for sure, the average insecticide won't work. Neem oil or some other chemical that states that it kills mite on the label. If you use neem oil, spray very thoroughly, and then keep the plant out of the sun and heat for a couple of days, and a repeat spraying in a week or two is also a good idea. If this plant is next to any other plants, they are probably also in trouble.

You might want to read these posts.
White, Dusty Splotches on leaves?

Rolled? Curled? Leaves w Spider Visitor

Scale Mite Infestation

Cynthia

[wisechild9]

I did wipe the bottom of the leaves and there was a rust coloured residue that came off,and some tiny looking specks, probably red mites. So I went and bought some insecticide soap spray from Home Depot (it was the only place still open last night). I didn't find any neem oil there. But the spray says it kills spider mites, so I hope it works. I will also try to increase the humidity in my solarium - I read somewhere that helps too.

[Anton]

I have posted photos of a bad case of scale infestation in the Diseases and Pests Picture Gallery. Check it out to see if that is hat it looks like.

[Cynthia, Prescott, AZ]

I have never seen humidity do anything for discouraging mites. I think that is an old wives tale. Well, maybe if the plants were outside and there was some balance of nature, it might shift the balance slightly. But in the home or greenhouse, you either have mites or you don't. You have to get rid of them 100.00000%, and then probably treat incoming plants on general principle to keep your collection clean. Cynthia

[wisechild9]

After a couple of weeks, I've sprayed with my insecticide soap (by Green Earth) a second time, and then again a week later. It seems that the problem is still spreading, but very slowly. I am wondering if I should switch to neem oil or a different insecticide soap, or increase the frequency of spraying with this existing insectide soap? Which route would you recommend?

Another question - I have a phal that is in bloom right now. It only has 3 leaves because I cut off the two bottom leaves that were in pretty bad condition with the mite problem. There is some mite damage to the second two bottom leaves. Would I be putting the phal in danger if I were to cut off the two bottom leaves and only leave the crown with one leaf? What is the minimum number of leaves that a phal needs in order to sustain itself? If there are no more leaves, but the roots are healthy, could it still survive?

[atcrosby]

My own personal experience is if the roots are healthy the orchid will survive as long as there is at least a leaf happening. Orchids are fairly tough but don't know if they are able to survive without a leaf. (Cynthia ? )

I would switch to Neem to help out in the battle. It has something that seems to work. Just follow the directions for them. As was posted earlier don't put it in direct sun after spraying since the oil will act just like tanning lotion does on skin magnifying the suns heat. Cooked orchid never goes over well!

Keep us posted.

[Cynthia, Prescott, AZ]

Don't remove those leaves! It will set the plant back severely and serves no purpose what so ever. The only thing wrong with those leaves, once you kill the mites, is that they are disfigured, but that does not affect they're usefulness to the plant. They will eventually pass on with age. If we are talking Phals and Catts, go ahead with the neem oil, with the above cautions after spraying. Spray very thoroughly, including some into the mix. Then a second spraying about a week or two later.

But, do you have any other plants in the vicinity? Everything nearby must also be treated. Mites are like grains of sand on the beach, they occur in large numbers, and you have to kill every single one. If there are other plants near by, there will certainly be a few wonderers on them. The added value of neem is that the mites don't like sprayed plants, for what ever value that is. In my greenhouse, the last time around, I did such a thorough job of spraying, that I only had to spray once to get rid of them all. Unfortunately, the over spray (plants that got double and tripple, +?, from the drift when other plants were being sprayed) caused some thin leaved and terete leaved plants to have a big setback. But the mites are truely gone. I have a few other chemicals that claim to kill mites, and I will be experimenting with them next time. Cynthia

[latsyrc]

Yeah, don't cut off leaves if you don't have to. I had one phal get some serious crown rot, which eventually caused it to lose all its leaves. It had a fabulous root system though, so acting on some good advice, I kept watering it just a little every now and then, and now it has a new crown and three leaves. It's been several months, though, and it's basically gone from a blooming plant to a seedling. So orchids can survive without leaves if they've got good roots, but it's not worth trying if it's not absolutely necessary!

how about trying a systemic like bayer advanced rose and flower? it lists spider mite as one of its targets?

[Cynthia, Prescott, AZ]

That part of the Rose and Flower that kills mites is not systemic, it is the Cyfluthrin, a synthetic pyrethroid. This is a contact poison, and you could be equally effective with the natural pyrethrin that is out there. I have used pyrethrin, and it does not have as long a lasting quality as neem, and I have had a few orchids that did not like it, especially the flowers. But then I have plants that don't like neem either. I have always used the pyrethrin on the flowers as a very light dusting to discourage slugs from ruining the flowers back in the days when I had a very bad infestation of slugs. So I guess, one could use the Rose and Flower spray, but it has to be a very thorough spraying, and probably repeated a time or two.

[flaorchidfan]

Hey, do you think it would be a good idea for this member to go ahead and cut the flower off so the plant can use that energy for growth. I know I hate cutting flowers but sometimes it will suck needed energy from the plant.
I just got some neem oil from schultz called "garden safe" in a concentrate. i just mix up a little in a dedicated spray bottle and spray away. and yes, keep them out of the sun after. the oil acts like baby oil or suntan accelerator and will burn the dickens out of the leaves.
hope all works out...

[wisechild9]

Update - well it's now February and I still have this mite problem. It kind of got better but now it's getting bad again. I am using a mixture of neem oil with soap and water. It's kind of difficult to have to keep my sprayed orchids out of light since 4 of them are budding right now. I find that maybe because of the spraying, their blooming has taken a lot longer than normal. I just think it's strange that even though some of my orchids are down to only 2 or 3 leaves, they are still spiking.

[Cynthia, Prescott, AZ]

The red under the leaf mites, as I have been reading, have a much longer reproduction life cycle than the spider mites. I think respraying every 4 weeks is better for them.