How to recognise it
Brunchorstia blight occasionally attacks Abies, Cedrus, Larix, Picea, Pinus nigra, Pinus sylvestris, Pseudotsuga and Tsuga plants that are growing on nurseries. It causes needle browning and tip dieback.
Coniothyrium pini (Rhizosphaera pini) produces small black spores with a milky white exudate.
Coryneum blight attacks young growth on Cupressus and thuja, girdling stems causing brown dieback in spring. In times of high infection, defoliation can occur. This blight usually infects through wound tissue.
Cercospora blight attacks plants in the family Cupressaceae, causing progressive browning, dieback and needle drop from lower, older needles upwards. Small red lesions can be found on older growth. New growth is not affected until it matures.
Didymascella (Keithia) needle blight on thuja turns individual sections on fronds brown. Damage can coalesce causing large areas of dieback. Fronds that have been infected for some time can produce a black spot in the centre of each section of damage. Spores are coated in a sticky film that helps them to remain viable for longer. They are released during the summer months in humid conditions.
Kabatina shoot blight attacks Cupressus, juniper and thuja from early spring onwards. Brown sections are produced as a result of constriction at the base of needles and stems. Small black pinhead spores are spread by water splash.
Pestalotiopsis needle/leaf blights usually attack weak plants or damaged tissue from pruning (in wet weather or because the tools are not sharp enough), insect attack, frost, water scorch or spray damage. Small black fruiting bodies (pycnidial spores) are produced and easily spread by water splash.
Phomopsis blight produces similar damage to Pestalotiopsis spp. but spores are white rather than black in colour. Plants that can be affected include thuja and juniper.
Sphaeropsis sapinea (Diplodia pinea) attacks new growth on Pinus spp. but usually only on plants under stress from issues such as drought. Infected needles turn yellow then brown and can stay attached to the plant. Black pycnidial spores are produced at the base of infected needles.
Red band needle blight (Dothistroma septosporum) symptoms can show from June onwards. This disease attacks the older needles of Pinus radiata and Pinus nigra. Yellow and light-brown spots on needles turn red quickly, although the needle base usually remains green. Black pycnidial spores are produced on the damaged sections.
Most tip blight diseases are spread by water splash, either through rain or overhead irrigation. Humid conditions encourage spores to develop rapidly. Plants can be re-infected from fallen plant debris.
Small sections of dieback can be seen on vulnerable plants. This can cause tip dieback and needle browning followed by large areas of brown dieback and needle drop. Damaged tissue can be vulnerable to other opportunistic pathogens.
Treatment: biological control
- Compost tea can help to increase competition for space on foliage with diseases.
- Coat vulnerable needles with an anti-transpirant to prevent wind and cold damage.
Treatment: cultural control
- Use sub-irrigation wherever possible. If overhead irrigation is used, try to avoid irrigating during late afternoon or evening so that leaf surfaces do not stay wet for long periods of time.
- Maintain good plant spacing to encourage airflow within the crop. Avoid high humidity in protected crops.
- Collect and dispose of all prunings that may carry disease over from one season or one crop to the next. Trim plants in the spring rather than the autumn. This prevents open wounds being exposed to long periods of cold weather.
- Clean thoroughly and disinfect beds and benches etc between crops.
- Keep nitrogen levels balanced in crops to avoid the production of very soft growth.
- At the early stages of infection, stems can be cut off and burnt.
Treatment: chemical control
Active ingredient Azoxystrobin
FRAC code 11
Formulation Amistar* (Syngenta)
Action(s) A systemic, translaminar fungicide with eradicant and protectant abilities - compatible with biological controls.
Active ingredient Bacillus subtilis strain QST713
Formulation Serenade ASO* (BASF/Bayer CropScience)
Action(s) Protectant bio-fungicide - compatible with biological controls.
Active ingredients Boscalid + pyraclostrobin
FRAC code 7 + 11
Formulation Signum* (BASF)
Action(s) Systemic, protectant and curative fungicide - compatible with some biological controls.
Active ingredient Chlorothalonil
FRAC code M5
Formulations Various including Bravo 500* (Syngenta)
Action(s) Contact, protectant fungicide. Take care with biological controls.
Active ingredient Copper oxychloride
FRAC code M1
Formulation Cuprokylt* (Certis)
Action(s) Contact fungicide - compatible with some biological controls.
Active ingredient Cyprodinil + fludioxonil
FRAC code 9 + 12
Formulation Switch (Syngenta)
Action(s) Systemic, translaminar fungicide with protectant, curative action and long residual activity - incompatible with biological controls.
Active ingredient Mancozeb
FRAC code M3
Formulations Dithane 945* (Interfarm), Karamate Dry Flo Neotec (Landseer)
Action(s) Protectant, broad-spectrum, non-systemic fungicide - compatible with biological controls.
Active ingredient Prochloraz
FRAC code 3
Formulation Octave (BASF)
End use date 30 June 2017
Action(s) Broad-spectrum protectant and eradicant fungicide. Take care with biological controls.
Fully updated by Dove Associates
Use plant protection products safely. Always read the label and product information before use.
* EAMU required for use in ornamental plant production outdoors and/or under protection.
Dove Associates shall in no event be liable for the loss or damage to any crops or biological control agents caused by the use of products mentioned.