Is it a Bug or a Fungus?

gillnurseryProblem Solving, Timely Tips11 Comments

We’re talking with customers everyday who are concerned that they have a fungus on their plants. My first thought is that it would be rare to have fungus this time of year since its so warm, windy, and dry. It’s much more likely to be a bug. Here’s how to identify and control. 


Is it white and cottony on the stems and flower buds? If so, you have Mealybugs! They show up in the Summer on Hibiscus, Jatropha, Purslane, Salvia and many more of our plants. You can treat with organic Spinosad soap or Bee Safe 3-in1 Garden Spray – be sure to spray in the evening due to our high temperatures. We recommend spraying the plant once a week for 3 weeks. 


Do your leaves look brown and speckled? Sounds and looks like a fungus, but this time of year, its most likely lace bugs on the underside of leaves. They are notorious for attacking Lantana. We’ve even seen some lace bugs on Zinnias and Persimmon trees this Summer. We recommend you cut your plants back one third to half, fertilize and then spray with organic Spinosad soap.

Scale and sooty mold on a Eucalyptus tree

Do your Crape Myrtles look black and sooty? This is a tricky one:  black sooty mold is a fungus, but it’s caused by insects. Aphids, scale insects, and whitefly leave behind a sticky residue (called “honeydew”) that black sooty mold grows on. If you kill the bug, then the soot goes away. Each of these can be controlled with organic Spinosad soap or Bee Safe 3-in-1 Garden Spray.  


11 Comments on “Is it a Bug or a Fungus?”

  1. What do I need to use on a crepe myrtle that like like a fungus on top of leaves with bugs on the underneath of the leaves? Do I need to cu it back? It is a young plant that was planted in the spring of 2020.

    1. Hi Carolyn – that’s the black sooty mold on top of the leaves and aphids/whitefly underneath the leaves. You can spray with Spinosad soap or Bee Safe 3 in 1. Be sure you are getting good coverage on the bottom of the leaves where the bugs are. Once you take care of the bugs, the sooty mold will go away.

    1. Texas Mountain Laurel is the host plant for its own caterpillar from a moth. You can spray with BT aka Thuricide which is an organic caterpillar killer safe to use on all plants including vegetables. We carry it in a concentrate, Ready to use or ready to Spray.

  2. Is it rust colored dots on the back of the leaves? If it is, that is called rust which is fungus. We are seeing lots of it now on Plumeria. You can spray with Neem oil in the evening or Liquid Systemic spray. Any leaves that drop be sure to gather them up and throw them away.

  3. James, it looks like I’ve again got take all root rot in a section of front yard grass that is not shaded and gets good
    drainage. I’m not overwatering. I put peat moss down in late winter. It was doing well and growing and greening nicely until about 3 weeks ago. Thoughts? Solutions?

  4. We’ve noticed an aggressive yellow fungus growing on our potted cabbage (with potting soil) on one lower leaf, on the top of the soil, and growing on the rim of the pot. Any idea what this might be?

Leave a Reply

Your email address will not be published. Required fields are marked *