Pest & Disease Factsheet - Needle blights

Prevalent in wet, humid conditions and particularly on susceptible crops grown under overhead irrigation, tip blights can adversely affect a range of conifer species.

Image: Dove Associates
Image: Dove Associates

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.

Biology

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.

Symptoms

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.


Have you registered with us yet?

Register now to enjoy more articles and free email bulletins

Sign up now
Already registered?
Sign in

Before commenting please read our rules for commenting on articles.

If you see a comment you find offensive, you can flag it as inappropriate. In the top right-hand corner of an individual comment, you will see 'flag as inappropriate'. Clicking this prompts us to review the comment. For further information see our rules for commenting on articles.

comments powered by Disqus

Read These Next

Tomorrow's tractors

Tomorrow's tractors

These machines have advanced rapidly over recent years but what does the future hold? Sally Drury looks ahead.

Climbing roses

Climbing roses

Walls, trellises, pergolas and even trees can all be brightened up by these beautiful blooms, writes Miranda Kimberley.

Pest & Disease Factsheet - Mealybugs

Pest & Disease Factsheet - Mealybugs

Vines, tomatoes and tropical plants are among those at risk.


Opinion... Shining a light on trading with Europe

Opinion... Shining a light on trading with Europe

Accurate figures are notoriously difficult to get at, but without doubt the UK imports a great deal of its ornamental plant requirement.

Opinion... Unbeatable delight of quality plants

Opinion... Unbeatable delight of quality plants

Viewing top-quality plants, both growing and on sale, always gives me pleasure.

Editorial ... More analysis and insight from bumper HW issue

Editorial ... More analysis and insight from bumper HW issue

Welcome to this bumper 72-page July edition of Horticulture Week magazine, packed with exclusive analysis, insight and expert advice on the biggest issues impacting all sectors of the UK horticulture industry right now.


Follow us on:
  • Facebook
  • LinkedIn
  • Twitter
  • Google +
Horticulture Jobs
More Horticulture Jobs

Tim Edwards

Boningales Nursery chairman Tim Edwards on the business of ornamentals production
 

Read Tim Edwards

Ornamentals ranking

Top 30 Ornamentals Nurseries by Turnover 2017

Top 30 Ornamentals Nurseries by Turnover 2017

Tough retail pricing policies and Brexit opportunities drive the top 30 growth strategies.

Pest & Disease Tracker bulletin 

The latest pest and disease alerts, how to treat them, plus EAMU updates, sent direct to your inbox.

Sign up here

Are you a landscape supplier?

Horticulture Week Landscape Project Leads

If so, you should be receiving our new service for Horticulture Week subscribers delivering landscape project leads from live, approved, planning applications across the UK.

Peter Seabrook

Inspiration and insight from travels around the horticultural world
 

Read more Peter Seabrook articles