Frequent rains during spring and summer resulted in increased leaf spot disease on crape myrtle trees in Northwest Florida.
This year’s high humidity and frequent rainfall provided ideal conditions for fungal and bacterial leaf spot disease development.
We began seeing evidence of leaf spot on many crape myrtles back in May and it has continued into late summer.
Initial symptoms included dark brown spots that developed first on the lower leaves and progressed upward in the canopy through midsummer. This will continue into fall and is resulting in early leaf drop on many crape myrtle trees in our area.
Infected leaves develop a yellowish to orange-red coloration then fall prematurely, particularly in highly susceptible varieties. Cultivars such as Natchez, Muskogee, Tonto, Sioux, Basham’s Party Pink and Tuscarora may be more tolerant but even these are showing some symptoms this year as a result of wet conditions throughout much of the growing season. New crape myrtle varieties with burgundy foliage seem to have less disease.
Long term, foliage diseases usually are not detrimental to a tree. However, plants growing in conditions that are not ideal will be more affected by leaf spot disease.
Use of fungicides to control leaf spot diseases usually are not very effective unless they are applied repeatedly on a regular basis with uniform coverage throughout the tree’s canopy during the entire time conditions are favorable for disease development. Getting adequate fungicide coverage on larger crape myrtles is also a problem.
Raking and destroying the fallen leaves may provide some help in preventing disease. But if a tree is otherwise healthy, foliage diseases should cause no long-term problem.