Leylandii Diseases
What is there too look out for when maintaining your Leylandii?
Botryosphareria Canker
The outward symptoms of Botryosphaeria canker, caused by Botryosphaeria dothidea, are similar to those of Seiridium canker; scattered bright reddish-brown dead twigs and branches occurring in otherwise healthy foliage. Cankers on small twigs and branches are also similar to those caused by S. unicorne, except that extensive resin exudation usually does not occur. Unlike S. unicorne, however, B. dothidea may produce long, narrow cankers on the trunk that might extend for a foot or more in length. These cankers rarely girdle the trunk, but will kill any branches that may be encompassed by the canker as it enlarges. Fruiting bodies of the fungus, perithecia and/or pycnidia, are produced just beneath the bark, but their presence can be discerned as tiny raised pimples scattered over the surface of the canker. Spread of the fungus is similar to that described above for S. unicorne, except that ascospores of B. dothidea may be spread by wind.
Botryosphaeria canker most often occurs on plants that are under considerable stress, and an effective control strategy should include keeping the plants growing as vigorously as possible. Mulch plants yearly and provide adequate water during extended dry periods. Avoid heavy fertilization and severe pruning of established plants. Prune out and destroy dead branches. Effective chemical control is not available.
Cercospora needle blight
Caused by the fungus Cercosporidium sequoiae (syn. Asperisporium sequoiae; Cercospora sequoiae), is a relatively new disease on Leyland cypress. However, it a common disease on species of Juniperus, Thuja, Cupressus, Taxodium, Cryptomeria, Sequoia and other genera. The first symptom of Cercospora needle blight is a browning of the needles in the lower crown next to the stem. The disease slowly spreads upward and outward until, in severe cases, only the needles at the tips of the upper branches remain green. In a general way, these symptoms mimic those caused by severe stress where the interior needles turn yellow and fall off. Fruiting bodies of the fungus appear as tiny, greenish pustules on the upper surface of the needles or on small twigs. Spores (conidia) are present throughout the spring and summer and are spread by wind. Infection usually occurs during long periods of wet conditions.
Cercospora needle blight can be controlled by spraying with copper-containing fungicides. There are no fungicides registered specifically for the disease on Leyland cypress, but Kocide is registered for general use on ornamentals. Spray plants at 10-day intervals from bud break until new growth starts.
Root Disease
2 root diseases may affect Leyland cypress; Phytophthora root rot caused by Phytophthora cinnamomi, and Annosus root rot caused by Heterobasidion annosum. Phytophthora root rot can be a problem in both the nursery and landscape, and primarily affects smaller roots on plants. Large established trees in the landscape are rarely affected by Phytophthora root rot. The disease is usually more damaging in situations where soil drainage is very poor. Plants with severe root damage may exhibit a general yellowing of the foliage and some tip dieback. Phytophthora root rot can only be diagnosed with certainty by laboratory analysis of affected roots. Control of the disease in nurseries can be obtained by treatment with Subdue Maxx. Chemical control is not recommended for landscape trees and plants.
Annosus root rot is usually associated with landscape plants. Initial infection by the fungus is by spores on the freshly cut stumps of conifers, most commonly pine. The fungus grows through the stump and its root system and may infect adjacent trees through root contact. The larger roots of the newly infected plants are killed and decayed. Top symptoms may include a yellowing and slow decline, followed by death of the tree; or the foliage on the entire tree may suddenly turn a reddish-brown color. Some trees may fall over before any crown symptoms are present. Fruiting bodies of the fungus may form at the base of the tree, usually beneath the mulch or leaf litter. These are usually small, irregular in shape, brown on the upper surface and white on the lower surface. There are no effective control measures once the tree is infected. As a preventative measure, stumps of felled, living conifers should be either removed completely, or the stump surface treated with dry granular borax immediately after the tree is cut.
What is there too look out for when maintaining your Leylandii?
Botryosphareria Canker
The outward symptoms of Botryosphaeria canker, caused by Botryosphaeria dothidea, are similar to those of Seiridium canker; scattered bright reddish-brown dead twigs and branches occurring in otherwise healthy foliage. Cankers on small twigs and branches are also similar to those caused by S. unicorne, except that extensive resin exudation usually does not occur. Unlike S. unicorne, however, B. dothidea may produce long, narrow cankers on the trunk that might extend for a foot or more in length. These cankers rarely girdle the trunk, but will kill any branches that may be encompassed by the canker as it enlarges. Fruiting bodies of the fungus, perithecia and/or pycnidia, are produced just beneath the bark, but their presence can be discerned as tiny raised pimples scattered over the surface of the canker. Spread of the fungus is similar to that described above for S. unicorne, except that ascospores of B. dothidea may be spread by wind.
Botryosphaeria canker most often occurs on plants that are under considerable stress, and an effective control strategy should include keeping the plants growing as vigorously as possible. Mulch plants yearly and provide adequate water during extended dry periods. Avoid heavy fertilization and severe pruning of established plants. Prune out and destroy dead branches. Effective chemical control is not available.
Cercospora needle blight
Caused by the fungus Cercosporidium sequoiae (syn. Asperisporium sequoiae; Cercospora sequoiae), is a relatively new disease on Leyland cypress. However, it a common disease on species of Juniperus, Thuja, Cupressus, Taxodium, Cryptomeria, Sequoia and other genera. The first symptom of Cercospora needle blight is a browning of the needles in the lower crown next to the stem. The disease slowly spreads upward and outward until, in severe cases, only the needles at the tips of the upper branches remain green. In a general way, these symptoms mimic those caused by severe stress where the interior needles turn yellow and fall off. Fruiting bodies of the fungus appear as tiny, greenish pustules on the upper surface of the needles or on small twigs. Spores (conidia) are present throughout the spring and summer and are spread by wind. Infection usually occurs during long periods of wet conditions.
Cercospora needle blight can be controlled by spraying with copper-containing fungicides. There are no fungicides registered specifically for the disease on Leyland cypress, but Kocide is registered for general use on ornamentals. Spray plants at 10-day intervals from bud break until new growth starts.
Root Disease
2 root diseases may affect Leyland cypress; Phytophthora root rot caused by Phytophthora cinnamomi, and Annosus root rot caused by Heterobasidion annosum. Phytophthora root rot can be a problem in both the nursery and landscape, and primarily affects smaller roots on plants. Large established trees in the landscape are rarely affected by Phytophthora root rot. The disease is usually more damaging in situations where soil drainage is very poor. Plants with severe root damage may exhibit a general yellowing of the foliage and some tip dieback. Phytophthora root rot can only be diagnosed with certainty by laboratory analysis of affected roots. Control of the disease in nurseries can be obtained by treatment with Subdue Maxx. Chemical control is not recommended for landscape trees and plants.
Annosus root rot is usually associated with landscape plants. Initial infection by the fungus is by spores on the freshly cut stumps of conifers, most commonly pine. The fungus grows through the stump and its root system and may infect adjacent trees through root contact. The larger roots of the newly infected plants are killed and decayed. Top symptoms may include a yellowing and slow decline, followed by death of the tree; or the foliage on the entire tree may suddenly turn a reddish-brown color. Some trees may fall over before any crown symptoms are present. Fruiting bodies of the fungus may form at the base of the tree, usually beneath the mulch or leaf litter. These are usually small, irregular in shape, brown on the upper surface and white on the lower surface. There are no effective control measures once the tree is infected. As a preventative measure, stumps of felled, living conifers should be either removed completely, or the stump surface treated with dry granular borax immediately after the tree is cut.