I recently submitted a Phalaenopsis leaf with the problem to my local county (San Francisco) State (CA) Agricultural Representative. I also gave him pictures of my Phals with the problem, a printed out copy of Steve Wilson web page http://www.geocities.com/tlswilso/Phal_problems_2-15-04.html, and a link Robert Pavlis web page http://www.orchidmall.com/general/microfun.htm . He was kind enough to help. He gave the information and leaf sample to a local plant pathologist, and the state agricultural lab in Sacramento, CA. The verdict: no fungus, no bacteria, and no virus. The plant pathologist opinion is that it is a physiological and cultural problem. Based on these results you can put away the various chemicals that have been thrown at the problem. As has been discussed on the OGD before, there are problems like flat spider mites and Septoria selenophomoides (fungus) that have similar symptoms. So the diagnosis of individual plants can be problematic. It would be interesting if people with Phals that have the problem submitted leaves to their state agricultural labs to see if they get the same results. If you live in Florida, it is very simple and easy, plus 20 bucks, to submit a leaf for evaluation. http://www.imok.ufl.edu/plant/clinic/index.htm I am fairly confident that fungus, bacteria, and known orchid viruses have been eliminated as a possible cause. I know that a number of people have had their leaves sent to labs to check for viruses and the results have always comeback negative. Jean Metcalf back in March 2004 on the OGD reported she had sent some leaves to a lab (Critter Creek Labs) and the results were negative for a virus. The leaf I sent was looked at through an electron microscope and no viruses were detected. The leaf sample I gave, I considered to be active with the problem. This does not totally eliminate the possibility of an unknown virus. I have been told: "The absence of virus under EM is not conclusive; as such low concentrations may exist that it won't be detectable." Back in February 2004, I decided to try and take a fresh look at the problem and consider all possibilities. This included the possibility of flat mites. Back then I asked one of the OGD's resident entomologists, Dr Paul Johnson http://nathist.sdstate.edu/orchids/Pests/mites.htm a few more questions about flat mites and trying to create conditions for them to thrive if they were around. He was kind enough to answer my questions. One thing he said: "One thing to note, though, and this is a problem that entomologists face, is that trying to raise arthropods is typically a much more difficult task that finding them in abundance." This has proven to be very true. I have searched using a 30x microscope for flat mites and have not found them. Two of my phals with the problem have gained no new spots, one other has gained a few new spots, but I could detect no mites of any kind. I know from past report by other people battling the problem that no one has yet seen mites along with the symptoms. I also think that the amount of various insecticides, fungicides, and other agents that have been sprayed and drenched on the problem would make it hard for mites to thrive enough to bring the demise of the plant. Note: I am using insecticides, and fungicides in the broadest layman definitions of the word. Besides an unknown virus this leaves us with a physiological and cultural problem. In my opinion, the only things that we seem to know for sure are that symptoms appear after Phalaenopsis endure a highly stressful period of time (either hot or cold temperature wise), and that they don't bounce back easily and are more likely to decline and become compost. I do hope to be able to prove that Phalaenopsis can bounce back. While it seems to me mine are recovering right now, it will take a few more clean leaves to prove it. I think pinpointing the cause and the cure to the Phal leaf problem is beyond my capabilities, but I may be able to come up with some possibilities. If anyone has insights or differing opinions, I would love to hear them on or off the list. The main goal is to get to the bottom of the problem. I do hope other people get their leaves tested, and report back. Mark Sullivan
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