For many years, Italian cypress trees stood tall and distinctly upright in area landscapes.
These remarkable columnar trees proved drought tolerant and wind resistant despite their height of 20 to 40 feet.
While the trees were susceptible to a few pests and diseases, nothing has affected Italian cypress like the current plague – Seiridium canker.
The North Texas urban environment has never been as hospitable for Italian cypress as their own native Mediterranean climate. Conditions such as drought, high humidity, lack of air circulation, excessive rainfall or irrigation or less than a full sun exposure tend to stress the trees and make them vulnerable.
This year’s weather, particularly high moisture and humidity levels, predisposed Italian cypress to disease.
Seiridium canker is a fungal disease that is now affecting stressed cypress trees across the state. It is responsible for the death and ultimately the removal of Leyland cypress trees throughout much of Texas. It is now a major disease in Italian cypress.
The first symptom of Seiridium canker can be a dulling of selected branches throughout the tree. The dark-green foliage first becomes gray-green and then brown. As the disease progresses, additional branches sport dead foliage.
The brown branches are sometimes referred to as “fox tails,” and they are an easy-to-spot indicator of Seiridium canker. Eventually, the tree’s central leader may brown and die.
There are no chemical controls available for treating or preventing this disease. The best plan for keeping cypress trees healthy is providing a site that is well-drained with good air circulation. Provide drip irrigation if possible so that the tree foliage is not sprayed with water.
Should trees become diseased, remove the infected parts. When pruning, make the cuts below the infection sites. Dispose of affected plant parts. Severely infected trees should be removed and replaced with a different species.
According to numerous authorities, there are no studies that indicate that any current Italian cypress varieties are resistant to the disease.
Another fungal disease that affects cypress trees is Phomopsis, which causes browning and tip growth death. Trees can generally overcome Phomopsis if they are otherwise healthy and grown in optimal conditions.
Phytophthora root rot is a soil-borne pathogen that attacks root systems. Trees affected with Phytophthora should be removed. Pests most likely to visit the trees include bagworms and spider mites, which can be managed with insecticides.
Attend the Lake Granbury Master Gardener butterfly festival, “Romancing the Monarch,” Sunday, Nov. 5, 1:30 – 4 p.m. at the Demonstration Garden behind Hood County Annex I, 1410 W. Pearl St. Learn how to support and protect monarchs as they migrate through Texas.
For answers to your horticulture questions, please call the Texas AgriLife Extension, Hood County at 817-579-3280 or go online to visit lakegranburymastergardeners.org.