Take a look outside, and you might see that your crape myrtle's leaves are turning shades of yellow, orange and red and falling to the ground. Is this a sign that autumn is near?
Not quite. This time of year, it's more likely you are witnessing something called Cercospora leaf spot.
"This is a very common disease we see late in the summer on crape myrtles," said Clark Robertson, an LSU AgCenter horticulture agent in Livingston Parish. "It tends to be worse in years where we get a lot of rainfall and humid conditions."
Cercospora leaf spot is a fungal disease that lurks in gardens year-round, waiting for the warm, wet conditions in which it thrives to attack crape myrtles. It releases toxins that cause small, yellow-to-brown spots to form on leaves. These infected leaves then change colors before falling prematurely.
"If you're seeing your tree dropping leaves in August with lots of fall color, that's a good indication that you have Cercospora leaf spot," Robertson said.
Some crape myrtle cultivars are more susceptible to the disease than others. While defoliation can be unsightly and even severe in some instances, the good news is that Cercospora leaf spot usually won't kill crape myrtles.
The best thing you can do is rake up any fallen, diseased leaves and dispose of them -- in the trash, not your compost pile, Robertson said. This will reduce the number of fungal spores in your landscape, helping prevent future infections.
"Treatment can be done, but it needs to be done early in the season to prevent infection from occurring," he said. "If you see the disease, it's already too late to spray."
Crape myrtles aren't the only plant affected by this disease. If you've noticed dark blotches or defoliation on hydrangeas lately, Cercospora leaf spot is probably the culprit.
As is the case with crape myrtles, Cercospora leaf spot is rarely fatal to hydrangeas -- nor does it typically interfere with blooming, Robertson said. Treatment is the same, too: If you want to spray a fungicide to ward off infection, do so in the spring. At this point in the year, just stay on top of removing affected leaves that have fallen to limit the disease's spread.