Q. From a distance I thought my Yellow Bells and Orange Bells shrubs weren’t getting enough water because the leaves started turning brown. But when I looked closer, I’m wondering if the brown leaves are because of a fungus on the leaves. Any thoughts?
A. Look at the leaves of your Tecoma, a.k.a. Yellow or Orange Bells, more closely and I think you will see that the surface of the leaf has been eaten or “skeletonized”. This chewing damage causes the leaves to turn brown; they become brown faster when it’s hot out. At a distance you see the leaves of your Tecoma turning brown and it may look like drought. Upon closer inspection, you get more detail and can see the insect damage to the leaves and not a disease.
|Skeletonizer damage on Tecoma spp. Yellow or Orange bells|
This shrub is native to the Sonoran and Chihuahua and deserts of the Southwest, all through central and even the northern parts of South America, but not the Mojave Desert where it needs slightly more water and warmer winter temperatures. Tecoma and this skeletonizer coexist together. The skeletonizer is the younger stages of a moth. It’s not clear if this insect will survive the low temperatures of our winter or not. If it does, as more Tecoma are planted, we may see more of this insect damage in future years.
This insect damage is common to Tecoma in warmer parts of the Southwest. It’s feeding damage by the young, a.k.a. larvae, of a moth given the common name Tecoma Leaf Tier Skeletonizer. This damage is like the skeletonizer damage we see on grapes but caused by the young of a different moth.
Right now, this insect doesn’t usually cause enough damage to warrant spraying an insecticide. Just pull off leaves when damage appears and drop them on the ground. If the damage gets worse in future years, then spraying might be warranted.
The pesticides of choice are “natural” insecticides called Bt and Spinosad. Apply these sprays just before you anticipate damage or at the first sign of damage. Bt and Spinosad products will kill the larvae of any moth or butterfly, whether it’s good or bad one so be careful.
Spinosad can be hard on honeybees so don’t spray plants that are flowering and spray at sunup. If you have no choice when to spray, and the plant has flowers, remove them and more flowers will be produced later.