View Full Version : Black soot

08-22-2004, 06:16 AM
I hope I am posting this in the right forum. I recently have discovered this black soot on the leaves of several crape myrtles on the property of one of my clients. It does not appear to be powdery mildew, as it does not have the white appearance I am accustomed to seeing. This soot does wipe off, but I was curious if anyone here could fill me in on what I am dealing with and the best way to treat it. Thanks in advance

08-22-2004, 10:33 AM
That is probably what is called frass, or the excrement of some type of scale.

Green Dreams
08-22-2004, 11:06 AM
sooty mold grows on the "honeydew" secreted by aphids. Look under the leaves for them. If the aphids have been controlled, you are seeing the result of their infestation. Those leaves will drop soon anyway. Whiteflies and scale can cause the same problem. It's the sugars that the mold feeds on. Dump out some soda and mold will grow on it as well...

08-22-2004, 02:46 PM
thanks for the input guys...

08-22-2004, 05:01 PM
If there are small brown lumps on the branches. Then the sooty mold is caused by Lobate Lac Scale. Only teatment is root drench with Merit.

09-26-2005, 07:39 PM
Is their any particular product that can be used to get rid of the mold after it appears on Crepe Myrtle leaves. I have a big problem in SC.

09-27-2005, 12:23 AM
Is their any particular product that can be used to get rid of the mold after it appears on Crepe Myrtle leaves. I have a big problem in SC.

While Merit is a great product and prevents Sooty Mold it is Good old Soap and Oil that will take care of the cause and eliminate the Sooty Mold. The cause of Sooty Mold has been Explained very well, the protocol for treating it has not.

A 2 % solution of Insecticidal soap and 2 % ultra Fine oil is the quickest and cheapest way to cure and eliminate sooty mold. The Mixing instructions would be 2.5 Oz of soap and 2.5 oz of Ultra Fine Oil per gallon of water. The best application would be done close to sunset and allowed to sit over night. All surfaces of the plant leaves both top and bottom should be treated. In the morning after the sun comes up but doesn't reach very high in the sky, this treatment should be washed of with a garden hose at fairly hard pressure. Most of the Sooty Mold should wash off and the soap and oil with have killed most all of the insects that caused the problem. Should there be such a infestation that all of the Sooty Mold doesn't come off then repeat applications should be applied. It is import in the heat of a dry summer to be sure and not allow the oil to remain on the leaves during high sunlight hours. This will cause sunburn of the leaves.

If The Plant is covered completely with Sooty Mold and is Black all over. Then the second application should be Copper Sulfate and depending on the AI, mixed according to label instructions. General about 2/3 of a OZ per gallon. Once again evening application and morning rinsing works best. The longer the product can stay wet on the leaf surface the better the results, these are contact chemicals.