Cucumber Mosaic Virus (CMV) on Houstonia

It has been interested to see the wide range of symptoms that can be caused by virus. We received plugs of Houstonia caerulea into the diagnostic lab last week with leaf spots and dieback on the flower stalks. The spots themselves had a orange brown color. The root systems looked great-white, healthy looking, not pot-bound.
We incubated a few plugs in a moist chamber and plated the leaf spots onto CMA and PDA. No fungal growth and no sporulation ever occurred. There was also never any bacterial growth or streaming noted. Running out of possibilities , I decided to test with an AgDia combo strip for CMV, INSV, TSWV and TMV. The Houstonia tested postive for Cucumber Mosaic Virus (CMV)! I reran the test to confirm and again it was positive. I haven't been able to find a record of Houstonia being a host for CMV, yet (I'll admit I haven't done a concise search). The symptoms are interesting-with bright orange speckles on the leaf tissue and stems. (Click on any photo for a larger version.)

Close-up of foliage-note orange speckling.

This is the base of the stem, which also showed the orange speckling.

CMV is spread by aphids but also by mechanical transmission-meaning that workers can spread the virus when taking cuttings or otherwise moving infected plant sap.

Free Phytophthora online course

Are you interested in learning more about the disease Phytophthora and how it can affect your nursery?
Oregon State University and the Oregon Department of Agriculture have developed a FREE online course to help you identify and manage Phytophthora diseases in nurseries. This FREE course is also now offered in Spanish! The course is divided into three modules which take 60-90 mins each to complete.

If you're interested in receiving certification, OSU offers a Certificate of Mastery on Phytophthora from Oregon State University Extended Campus ($100 charge and online exam). But the information contained in the course is offered FREE! This is a great resource for nursery growers and I encourage you to check it out!

ProGreen 2009: Intro to Biocontrol of Insects in Greenhouses

Here is another presentation given at ProGreen 2009: An introduction to biological control of insects in the greenhouse.

Introduction Biocontrol Insects For Greenhouses

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ProGreen 2009: Intro to Greenhouse Diseases

Did you miss a seminar at ProGreen 2009? Check out the Intro to Greenhouse Diseases given as part of the Certified Greenhouse Grower track!

Plant Disease Talk at ProGreen2009

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Upcoming Pest Management Conference, Feb 19-21

Are you interested in learning more about the newest greenhouse insect and disease management strategies? Consider attending the 25th Annual Pest Management Conference in San Jose, California, Feb 19-21. The conference is presented by the Society of American Florists (SAF) and Greenhouse Grower. The lineup of speakers look great!
For more information or to register visit www.pestconference.org

Possible Phytotoxicity on Cordyline

These are Cordyline australis 'Southern Splendor' from a finishing operation. The main symptoms are the distorted growth and fusing together of the 'middle-aged' growth . The new growth is unaffected while the oldest growth shows tip burn. The plants were heavily infested with two-spotted spider mites (Tetranychus urticae) with obvious symptoms of yellowing and stippling present. The question from the grower was, "Is the distortion caused by the mite injury or is some other factor involved?"

Mite infestations are not known to cause such extreme symptoms so we needed to look elsewhere. The most likely cause is phytotoxicity caused by an pesticide application. The grower is looking into their rotation of miticides as mites have been a constant problem in this crop. Since they are a finishing operation (meaning they received the plants a few months earlier to grow to the final selling size) the grower may have difficulty tracking down what pesticides were applied before they took possession.

These symptoms have been seen by diagnosticians in other states, but a definitive cause of the problem has yet to be identified.

Tip burn was seen on the oldest leaves. Cordylines can be very sensitive to fluoride levels in irrigation water which can manifest as tip burn, but fluoride is unlikely to cause the other symptoms.

Two-spotted spider mites and associated injury (yellowing and stippling of older leaves) was observed.

Vinca minor-CMV (Cucumber Mosaic Virus)

This sample is Vinca minor from a propagation operation. The sample tested positive for CMV (Cucumber Mosaic Virus) using an Agdia immunostrip test.
CMV has a very wide host range and affects both vegetables and ornamental plants. Aphids are the primary source of infection but infection by mechanical transmission (taking cuttings, etc) is also possible. Infected plants should be destroyed to avoid spreading the virus within a greenhouse.