Growing Italian Cypress in North Central Texas Landscapes Presents Numerous Disease and Insect Challenges
Link to 2018 Publication from Texas A&M AgriLife Extension: Diseases of Italian Cypress and Related Species in Texas
For years, the Italian Cypress has been the exclamation mark in North Central Texas landscapes. Few trees or large shrubs provide such a columnar element of grey-green evergreen foliage. Landscape architects and gardeners alike have selected and planted Italian Cypress to accent building architecture and to add drama to pools and backyard terraces. What plant selection could be better for providing landscape screening when height is a necessity and width must be restrained.
Recently, Italian Cypress, Cupressus sempervirens, has found our urban environment to not be as hospitable as it native Mediterranean origins. Periods of high humidity, lack of air circulation, prolonged rainfall, excessive irrigation, and less than full-sun exposure in both residential and commercial landscapes has created an environment where Italian Cypress are stressed and predisposed to plant diseases and insect pests. What was once a landscape asset has, in many circumstances, become a landscape liability. Here are the disease and insect challenges that come with growing Italian Cypress in North Central Texas.
Seiridium Canker is a fungal disease caused by the pathogen Seiridium unicorne. It has become a major disease of Italian Cypress, and is responsible for the death and removal of most Leyland Cypress throughout much of Texas. The first symptom of Seiridium Canker can be a dulling of selected branches throughout the tree. What is usually dark-green foliage becomes grey-green, and turns progressively brown. The appearance of scattered branches of dead foliage is referred to as “flagging”. As the disease progresses, additional branches are flagged and the central leader may brown and die.
There are no chemical controls available for treating or managing Seiridium canker. The disease can only be managed by removing infected parts of the tree at a place below the infection site, and properly disposing them. Severely affected trees should be removed. Currently, there are no studies that indicate any varieties of Italian Cypress are resistant to Seiridium Canker.
Phomopsis Tip Blight
Phomopsis is a fungal disease that causes the browning and death of tip growth on Italian Cypress. While the damage is not as dramatic as that caused by Seiridium Canker, an excessive amount of Phomopsis Tip Blight can damage the overall aesthetic of an Italian Cypress. Browning starts at the growing tips and works its way down the stems a few inches. The damaged foliage is unsightly and difficult to remove by pruning simply because of the number of infected sites and the height of the trees. Italian Cypress can outgrow the damage when their general health is good and conditions that favor Phomopsis is temporary, such as a string of warm humid days with little wind. Phomopsis can be managed with various chemical fungicides and by providing cultural practices unfavorable for the disease. Those practices include a full-sun exposure, good air circulation, and keeping moisture form irrigation systems off the foliage
Phytophthora Root Rot
Phytophthora is a soil-borne fungal disease that attacks the root systems of Italian Cypress and other susceptible trees. It is most frequently found in soils with poor drainage. There is no chemical fungicide to manage the disease. Phytophthora enters the plant through the root system. As the roots decay, the tree becomes stressed and the Italian Cypress tree begins to decline. Italian Cypress showing signs of Phytophthora should be removed. Replacement trees should be resistant to Phytophthora and the planting are should be improved by increasing drainage.
Bagworms are a common insect pest on Italian Cypress and other conifers. They are easily identifiable by the cocoon-like structure they tote around as they feed on foliage. The silk structure is carefully covered with bits of needles providing some camouflage as it moves from stem to stem. Bagworms become active in May and usually complete their life cycle in just a few months. When numbers of feeding bagworms are low, damage to Italian Cypress may not be noticeable. But when this caterpillar is present in large populations, the damage is severe and can result in complete defoliation and death to the host tree. Fortunately, Bagworms can be managed with several insecticide sprays.
Spider Mites are insect-like pests that are commonly found on Italian Cypress, conifers, and other landscape plants. Spider Mites are almost microscopic in size, but can do significant damage to Italian Cypress when present in large numbers. As they feed on the needles they destroy the chlorophyll in the needles, causing the foliage to become dull. When present in large numbers, there will be fine webbing throughout the foliage where they are feeding. Spider Mites species prefer the hot and dry environments where Italian Cypress grow best. However, Spider Mites can be a serious pest problem any time of the year. Spider Mites can be best managed with systemic insecticides.