Monday, February 9, 2009

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.

Friday, February 6, 2009

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!