During the last week, four different individuals complained about a clean wound on pecan, oaks, persimmon and elm trees.
These descriptions made the diagnosis very easy.
Figure 1. The twig girdler and her damage on pecan. Image from LSU AgCenter
This cause of this damage is the twig girdler beetle.
According to the LSU AgCenter website, “This is a long-horned beetle with a grayish-brown body and long antennae. Larvae are found in the twigs and are up to one inch in length and light brown in color.
The beetle has a one-year life cycle. The female deposits eggs in small scars chewed through the bark and then chews a continuous notch around the twig, girdling it. Girdled twigs die and fall to the ground where the eggs hatch. Girdled twigs look like a beaver has worked them over. Development of its life cycle is usually in August when the adult emerges to repeat the cycle and why you are seeing the fallen branches.
Chemical control is impractical. Fallen twigs can be gathered and disposed of in fall or spring as this will destroy the larvae inside the twigs.”
A landscape professional brought in an azalea branch from the home of a client. This branch sample had a couple of problems.
Figure 2. An azalea branch with a couple of problems.
Dr. Raj Singh, Plant Disease Specialist, identified one problem, “The damage is caused by Azalea lacebugs. They usually feed on the underside and damage on the top results from their feeding injury.”
Prof. J. Stevens, Soil Fertility Specialist, commented on the second problem, “that potassium was rated as Low and Sulfur was rated as low.” Stevens recommended specific rates of muriate of potash to fix the potassium deficiency.
He also recommended ammonium sulfate to improve sulfur levels.
Terry brought in some red oak leaves infected with leaf spots.
Figure 3. A red oak leaf with tubakia leaf spot
According to the Texas Agrilife Extension website, “This disease is most severe in late summer and early fall. This disease is more prevalent during years that are wet. Also, this disease often occurs on oak trees that are under various stresses such as nutritional deficiencies, in particular iron deficiency. Newly transplanted trees are more susceptible to attacks by this fungus than well-established trees.
Determine the stress factors that may be predisposing the oak tree to this fungal pathogen. If possible, correct the conditions to minimize stress on the tree. With newly transplanted tree, ensure proper mulching and fertilization to encourage establishment.
Infected leaves should be collected and destroyed to minimize the spread of the disease. Removal of some branches to increase air movement will also help minimize incidences of tubakia leaf spot. Trees that are severely defoliated by this fungus should be fertilized slightly more than normal to stimulate new growth. Although chemical treatments are not warranted, several broad spectrum fungicides are available for use as a preventative measure.”
If you want to contact Roots, Shoots, Fruits and Flowers, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 337-463-7006 or firstname.lastname@example.org. Also, please share the name of your parish.