Will fall show its colors? Why are twigs falling?
One of my favorite things about Oklahoma is the distinct seasons we enjoy.
Autumn in Oklahoma is always something I look forward to after our hot summers. In central Oklahoma, the fall season sometimes provides spectacular leaf color displays.
Will this be one of those seasons? And what causes those green leaves to turn colors in the fall?
The green in leaves is caused by the presence of chlorophyll, which is responsible for catching the sun’s energy and converting it into energy for plant growth. During the summer, the chlorophyll is high and masks other pigments in the leaf. When fall approaches, the chlorophyll declines, and the other pigments in the leaf tissue shine through.
As the chlorophyll declines, we begin to see purple, red, yellow, orange and brown colors. But we all know that autumn tree leaf colors seem to vary from year to year in their intensity.
Ideal weather conditions that lead to the spectacular fall colors are bright sunny days and cool nights. Prolonged warm spells in the fall and cloudy, rainy weather can lead to poor fall colors. Dryer soils in fall, but not necessarily drought conditions, also lead to brighter fall colors.
With that in mind, we will always have varying fall color intensity, since our Oklahoma weather always varies! It was fairly warm this year, and we have had a lot of cloudy days and rain, but hopefully we will still have a nice show.
Beware twig girdlers
We have been getting many calls and emails at the Extension Center from individuals who are seeing many small branches from the tips of trees lying on the ground. These tip branches often are found under oak, pecan and other trees. They are quite messy and often have to be picked up from sidewalks and driveways, etc.
These small, fallen branches accumulating on the ground are a good indicator of an insect called a twig girdler. We evidently are having a record year for this insect.
The twig girdler is a small beetle that has one generation in Oklahoma each growing season.
The twig girdler female chews a V-shaped groove around a small twig, girdling it. She then will lay an egg underneath the bark on the girdled limb. This portion of the limb dies quickly and will fall to the ground with the larva inside. The small larva will overwinter in the fallen twig.
During the following spring, the larva resumes feeding, consuming most of the wood. As the larva grows, it bores further down into the twig and fills the tunnel with wood shavings and waste. Pupation occurs in a cavity within the twig. Adults emerge in late summer and early fall, and it all starts over again.
The best way to control twig girdlers is with good sanitation practices. Homeowners should collect and eliminate or destroy infested twigs and branches they find on the ground, beginning in the fall or early spring. This will eliminate the over-wintering larvae.