Question
Hi,
 My pelargonium are dying very rapidly, one after another, I don't know what happen.I noticed that it started in the stem, it just turn brown and subsequently the brown part will spread to the root and the other half needlessly to say turn brown and most of the time the leaves also
yellow. now, the roses,crysanthemum and other plants also got it, can u please help?

regards,
irene

Answer
Irene, your plants have been infected by a soilborne fungus disease. Without having a soil sample, it is impossible to speculate as to which one it is. Although fungus diseases are easy to prevent, they are extremely difficult to cure.

The easiest alternative is to spray them with a copper-based fungicide. I personally use a product called Soap-Shield from Gardens Alive, but there are many other copper-based fungicides available which will help halt the disease.  Attached is a link to Gardens Alive. They also offer many good illustrations of plant problems with suggest products to cure them. If you're interested in the Soap-Shield, just type it in their search field.  

http://www.gardensalive.com

My only concern is to what extent the disease has progressed in the soil. I strongly recommend that you take a 6" portion of a stem along with an 8 oz. soil sample to your local garden center or nursery and have them test it for disease. If it is determined that your soil is infected, you should not plant in that area for several months. Your best alternative at that point is to solarize the soil by placing 3 mil black plastic over the area to kill off the spores.  The decision is yours whether to apply the fungicide first, but I would personally start with the soil test and proceed based on the test results.  

I hope this information helps. Good luck, and please write again if I can ever provide assistance.  

Regards,  

Mike