Help! Its unsightly. It looks like a horrible disease that is suddenly covering multiple plants in my garden. Its even starting to show up on my patio furniture. You have just described sooty mold. Thankfully it is a non-harmful condition that will resolve it self when the root cause is eliminated.
So what is sooty mold, and more importantly, where does it come from?
Sooty mold is as its name implies, a fungus. It is a fungus that is growing on the surface of your plant, car, patio, and anything else underneath the infected tree. Unlike plant disease fungi, it is not directly feeding off of your plants. Sooty mold is growing on the honeydew secretions of insects.
In and of itself sooty mold typically will cause no real harm. Generally, the pest causing the sooty mold is of much more concern. However, in very heavily infested plants, it can reduce the plants ability to do photosynthesis resulting in stunted plant growth. Sooty mold covered leaves may also be more prone to dropping early. Plus, it can also make a really ugly mess of your patio. Fortunately, it can be washed off your car or patio with some scrubbing. Keep in mind though, that until you control the insects secreting the honeydew it is likely to quickly return.
Once you have removed the insect source of honeydew feeding the mold it will gradually disappear as it uses up its food source.
If you have resolved your pest problem, and the sooty mold is still present, do not despair. Your plant will be perfectly fine. There is nothing else that you need to do. Sooty mold may not completely disappear until the plant has shed and replaced its leaves the following spring. While impractical for larger plants, if you really can’t stand looking at the blackened leaves, you may be able to wash some of it off smaller plants.
What insects are responsible for causing sooty mold
Aphids and scale are the insects mainly responsible for creating the honeydew sooty mold loves to feed on. Both of them feed on sap from your plants and secrete honeydew as a waste product. This waste product is high in sugar, so it provides an excellent food source for the mold. While aphids and scale are the most common contributors, they are not the only pest that can lead to sooty mold.
The first step in solving the sooty mold problem is to identify what pest you have on your plants. Start by inspecting tender new growth of plants in the areas where sooty mold is present. It can also be helpful to do an internet search to learn what pests are common on the infected plant species.
Don’t forget to consider trees like crape myrtles that might be dripping honeydew on plants beneath them. Every plant with sooty mold might not be infected with a plant pest. Often a tree will drip onto adjacent plants. This will make it look like they have a problem when in reality they do not.
Different pests may require different methods of control. For example, aphids and scale must be treated and managed in very different ways. It is important to identify your pest accurately as treating for the wrong pest can not only not control the problem pest, but it can cause outbreaks of other pests compounding your problem.
Control the ants
One last thing we would like to note is that not only does sooty mold like to feed off of honeydew, but so do ants. If you have a plant that has sooty mold and a lot of ants present, you should take measures to control the ants. There is a good chance that the ants are farming the scale or aphids for the honeydew. In this scenario, the ants are protecting the pest from the beneficial insect predators that would normally keep them under control. Sometimes controlling the ants can go a long way towards resolving your sooty mold problems.
We hope this alleviates your despair over your plants turning black on you, and sets you on the path to a greener garden!
If you would like to learn more about plant pests and other gardening topics, don’t forget to sign up for our newsletter!
Please remember
The information provided is for general informational purposes only. All information on the site is provided in good faith, for general informational and educational purposes only and is not a substitute for professional advice. We make no representation or warranty of any kind, express or implied, regarding the accuracy, adequacy, validity, reliability, availability, or completeness of any information on this Site. Accordingly, before taking any actions based upon such information, we encourage you to consult with the appropriate professionals. We do not provide any kind of professional advice. THE USE OR RELIANCE OF ANY INFORMATION CONTAINED ON THE SITE IS SOLELY AT YOUR OWN RISK. View full disclaimer here.
