Part 1 Mites that thrive in humid conditions and orchid fleck virus, a case study.

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quietaustralian

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Mites that thrive in humid conditions and orchid fleck virus, a case study
by Peter Hall, South Australia.

I found this document on the Cymbidium Club of South Australian's Facebook page and found it very interesting and enlightening. Peter Hall has kindly granted permission to repost this document here. Thankyou Peter.


More on orchid fleck virus by Peter Hall
Part 1
Two to three years ago some of us noticed that the leaves on our cymbidium orchids had streaky yellow flecking on them. We spoke to a few people and some of which were fertilizer supply businesses. Most people including the fertilizer suppliers said that it was a deficiency and indeed when we looked on the internet the symptoms certainly looked like a deficiency. We were advised to add magnesium and Manganese to our fertilizer regime.

We added Magnesium and Manganese over a period of time and waited to see some sort of improvement in the look of our plants but there was none. We were at a loss as to what the problem was, we didn’t think that it was a virus because we tested several plants for virus Odontoglossum Ringspot Virus (ORSV), Cymbidium Mosaic Virus (CyMV) and Tobacco Mosaic Virus) and the tests proved negative to these viruses.

Some of the flecking was now turning black. Time went by and we had many discussions with numerous people and the general consensus was that it may be a fungal problem caused initially by a bacterial infection and then progressing to a fungal infection.

Wane took an infected plant and some leaves up to South Australian Research and Development Institute (SARDI) Waite Research Precinct URRBRAE SA

Wayne had an appointment with Barbara Hall PLANT DIAGNOSTICIAN HORTICULTURE PATHOLOGY. Barbara took one look and said that it was a virus.
Several of the infected leaves were then sent up to a plant pathology testing facility in Queensland.

The spell of humid weather plus our fogging seemed to have accelerated the problem we were discovering more infected plants as the days went by. The speed at which the flecking seemed to be moving through our plants suggested that it was not a virus but a fungal problem.

We travelled out to Complete AG and Seed Supplies (agriculture and horticulture supplies). Virginia and whilst we were there discussing our problem a horticulture consultant called Vic Szabo called in and as happened Wayne had an infected leaf with him and he showed it to Vic and he said that it looked like it may be a fungal problem Anthracnose Collectotrichem Gloeosporlioides. Vic recommended using a product called OCTAV Wp a Group Y systemic fungicide used in conjunction with a wetting agent called SYNERTROL HORTI . One or the ingredients in the Synertrol solution is tea tree oil and this would kill off any scale insects.

Vic also asked if we sterilized our potting medium before using and suggested that we should seriously think about doing so and he recommended Condy’s Crystals (Potassium Permanganate). The dilution rate for Condy’s Crystals is 40g/10 litres.

We left there happy that we had solved our problem and came home, drenched and sprayed our plants and eagerly awaited some sort of result.

I was speaking with the secretary of the ACS Kevin Butler (EZI-GRO ORCHIDS) in Western Australia and our problem came up during our conversation. I explained the symptoms and what the plants looked like and he said that it sounded very much like orchid fleck virus and that it was spread by a false spider mite and of course we did not believe that scenario because of the large number of plants that showed up in a short space of time.

Wayne had spoken to a grower in Victoria and said that he had the same problem and that he had Quarantined the suspect plants, stripped them back to bulb only and that the new growth looked healthy. That was about 2 years ago.

Horror upon horrors Wayne received the test results from SARDI and the result was that the plants had orchid fleck virus

Wayne went around to one of our members place Vic Haskard and showed him one of his infected plants and Vic said straight away that it was orchid fleck virus and that he had it in his collection about 3 years ago. Vic had his plants tested for the virus.

We now know that there are several growers that have the same problem and that we will have to be vigilant in our approach to identifying this virus especially when plants are brought in to our club meetings and shows

Orchid Virus
Viruses are organisms invisible to the naked eye. They can only be seen through transmission electron microscope.

There are approximately 30 different viruses infecting orchids in various regions of the world. There are three that we as cymbidium growers are now familiar with
  • Odontoglossum Ringspot Virus ORSV)
  • Cymbidium Mosaic Virus (CyMV)
  • Cymbidium Fleck Virus (CFV)
Orchid Fleck Virus is far worse than ORSV, CyMV, because it is spread by sap to sap transfer (poor hygiene) and more importantly by False Spider Mite – Brevipalpus Californicus (Archnida Arari: Tenuipalpidae).

Brevipalpus Californicus has an extensive host plant range and they are about half the size of the Red Spider Mite (228 microns long) and they do not spin a web.

This mite and the spread of Orchid Fleck Virus is a very serious situation because the infection may not show up in our plants for 24 months or more.

The virus affects the plants and then the plants end up with a fungal problem.

Important: Identify the infected plants and dispose of them because the spread of this virus is incredible. There is no cure.

These false spider mite love humidity so all our good work, installing foggers make for a wonderful habitat for these critters!

Two Spotted Mite (Red spider Mite) thrive in hot dry conditions.

What to do
Dispose of all infected plants and set up a mite eradication program.

We have purchased a product from Complete AG and Seed Supplies at Virginia, just opposite Virginia Nursery. The product is called OMITE. Omite came on the market to replace KELTHANE for the two spotted mite.

This insecticide is an Aracicide because the mites are in the spider family. This insecticide is by contact it is not a systemic insecticide so we must make sure that we have complete coverage. Completely wet the leaves on both sides and around the bulbs. Make sure to de-husk the bulbs prior to spraying.

Program
Spray every 5 days for four applications then every 14 days.

I would then recommend using dissolving sulphur every 28 days and even use a systemic insecticide now and again because if we use the same chemical all the time, mites become immune to them.

Host plants for the False Spider Mite are numerous. All Acacia, Callistemon, Citrus, Croton, Dendrobium, Jacaranda, Lycaste, Poinsettia, Rhododendron, and many more. Just about all plants are hosts.

Part 2 http://www.slippertalk.com/forum/showthread.php?t=25485
 

Ozpaph

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A few pictures would be so helpful.
Thanks for posting the information and thanks to the author for giving permission.
 

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