This has been the most informative Article on whitefly infestation! Thank you. We have heavy infestation. We have used orthomax once every 10 days about 4 times now and to no avail. We go all around the plant and saturate from top to bottom. We are considering knuckle cutting (which we have not done in the past) our crepe myrtles, just to get rid of the bugs, as this seems to be their plant of choice. They stink and the sooty mold is dripping from our crepes onto our indian hawthorns which reside directly below. (our mulch is even black….where it was once red … yuk)
We appreciate your tips and are thinking we may have to go with the fogger, but at this point leaves are truly getting sparse on the crepes. My question now is how do we get the sooty mold off the plants below short of cutting them back drastically? Is there anything we can spray on them to rid the leaves of the mold once we get the whiteflies under control?
Thanks so much for your help.
Sooty mold is a fungus which will grow where honeydew drops and accumulates. Whiteflies feeding will many time cause of a lot of honeydew to drop down and when this happens on dirt, it generally goes unnoticed. If this happens on plants, the honeydew will disperse and quickly enable fungus (like sooty mold) to start growing which it sounds like you have happening now.
Before you attempt to work on the sooty mold, there are two more important things you need to address first.
1) Have you checked the soil PH around these plants anytime recently? First and foremost, it’s imperative that the PH be at least 6.5 if not 7.0 if you wish to get any kind of results from the pesticides you apply. As explained on our SOIL PH CONTROL site, it’s very important to monitor this measurement taking readings at least twice a year if not more. This is especially true when you find insects and fungus present. No doubt a low PH will lead to both these conditions and though it’s not directly responsible, failure to maintain the proper PH will most certainly lead to complications of all sorts including fungus and insect infestations.
2) Get the whiteflies controlled before you start to deal with the sooty mold. At this point, the products and treatment methods explained in our WHITEFLY CONTROL ARTICLE need to be implemented. I would say some BIFEN and NYLAR are going to be the best spray for this situation given the history you presented. And though a FOGGER could be used to apply it, a regular PUMP SPRAYER would do the job as well. The point is you need to treat this problem aggressively till it’s resolved and then deal with the Sooty Mold afterward.
Once you have the PH in check and Whiteflies under control, you will find the sooty mold will die off naturally. Without fresh honeydew on which to feed, it will run out of food and basically die. To help expedite this process, you can wash affected plant leaves with nothing more than water but until the honeydew supply is stopped, washing won’t help. So again, get the soil and whitefly situation under control and the sooty mold will be easy to remove. Good luck!!