Plant Disease Information
Ramularia causing issues for Daffodil growers
A recent diagnosis at the Ashtown plant clinic has confirmed it's Ramularia season for Daffodil growers. On this occasion, the variety 'Standard Value' seems to be badly affected. Ramularia causes a disease commonly known as 'White mould'
White mould. Infects the leaves and stems of daffodils, resulting in foliar lesions, eventually causing leaf death.
Lesions are found on both sides of leaves, starting as small, sunken off-white streaks predominately near the leaf tips. Spots later progress to yellowish spots covered with white mould. Resting spores known as sclerotia are immersed in the leaf, dark brown in colour. The fungus survives in the dead plant material as sclerotia, which then germinate to produce fungal spores. White mould is also spread between plants during wet and windy conditions.
If present, the disease usually develops just after the first leaf emergence (January). Cool, dry weather can reduce disease spread.
The most effective means of control of the disease is removal of the dead material as practicable. It has been suggested that daffodils are not replanted for a year as this is sufficient to kill off the remaining conidia and sclerotia. If this is not possible it is also suggested that replanting with more resistant cultivars can help to reduce the occurrence of the disease.
This species of Ramularia was originally described from northern Italy detected in England less than ten years later and since then has spread through Western Europe and, more recently, has been found in Eastern Europe. It appeared in an outbreak in the western USA in the early 1930s but does not appear to have spread further in North America apart from into the adjacent part of Canada. In the UK, it has been severe in the Channel Islands, Scilly Isles, Cornwall and Devon. It was reported as being common in Scotland in the late 1920s and 1930s but not so much after that although it was generally thought to be confined to Narcissus, although it was recorded on a specimen on Pancratium maritimum from Portugal.
J.C. David, 2004. IMI Descriptions of Fungi No.1609, CABI Bioscience, Egham, Surrey.
The Xylella bacterium causes wilting and death of plants. It enter the water-conducting xylem vessels where it multiplies and blocks the transportation of water. As spittle bugs feed on the fluid from the plant xylem they can become infected by the bacteria and pass it on to other plants. The 3 different supspecies of Xylella fastitiosa present in Europe are fastidiosa, pauca and multiplex. The bacteria are very specific in their hosts and may not effect closely related plant species or even some varieties.
The bacterium is a major concern for a few reasons; it is devastating most likely fatal to its host, it has a very wide host range 60 + plant species that show symptoms and more than 240 that can carry the disease without symptoms. Its vectors, spittle bugs, can be found all across Europe so it can easily be spread. To date there is no cure for the bacteria.
The European Commission have published the latest update of host plants susceptible to the bacterium Xylella fastidiosa in the union territory (16/1/2017 https://ec.europa.eu/food/sites/food/files/plant/docs/ph_biosec_legis_emergency_db-host-plants_update08.pdf) .
There are now over 300 known host species susceptible to the bacterium, though not all of these species develop disease, and not all species are affected by all Xylella subspecies (pauca,multiplex,fastidiosa,sandyi ) .
The list of host plants includes many common trees and ornamentals relevant to the Irish horticulture industry including Acer, Aesculus, Brassica, carex, Cornus florida, Fuchsia magellanica, Ginkgo biloba, Hedera helix, Hemerocallis, Hydrangea paniculata, Liquidambar styraciflua, Liriodendron tulipifera, Magnolia grandiflora, Olea europaea, Platanus, Prunus, Quercus, Rosmarinus officinalis, Rubus, Salix, Veronica, Vinca. The full list of susceptible plants is available here: http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32015D0789&from=EN .
X.fastidiosa was first regulated at EU level as a harmful organism with quarantine status in 1992 (Directive 2000/29/EC) but was not confirmed in Europe until 21st October 2013 when an outbreak of X.fastidiosa subsp. pauca was detected on olive trees in the Apulia region of Italy.
Reaction from the EU commission was swift with emergency measures published on 13th February 2014 which aimed to prevent the spread of X.fastidiosa within the union (Decision 2014/87/EU). This was quickly followed in July 2014 by the publication of more detailed measures to prevent disease introduction and spread within the EU.
Despite the introduction of these emergency measures, further outbreaks were reported in the neighbouring Italian province of Brindisi on the 9th of March 2015, Corsica on the 27th July 2015 (on Polygala myrtifolia) ,and the French mainland in the region of Provence-Alpes-Cote d’azur on 18th September 2015.
Detection and spread
Sap-sucking insects are important potential disease vectors once disease becomes established in an area. The primary risk comes from movement of infected material which means Irish plant importers will have to be vigilant in the sourcing and subsequent monitoring of imported host plant material.
Symptoms on plant material include dieback, stunting and leaf scorch, all of which are symptoms of many other plant pathogens and environmental factors such as frost damage. This makes a laboratory diagnosis necessary and involves identification of the disease at the molecular level by DNA extraction from infected material.
The ability of X.fastidiosa to ‘hide’ within asymptomatic plant material adds an extra layer of complication to its detection and control.
Suspected cases of this disease should be reported to the Plant Health Division of the Department of Agriculture Food and the Marine (DAFM). DAFM can be contacted as follows:
Horticulture and Plant Health Division,
Department of Agriculture, Food and the Marine,
Backweston Administration Building,
EU territory Latest Developments of Xylella fastidiosa - updated every 15 minutes
Botrytis infection on Paeonies'
High Risk periods
Damp, humid, wet-weather. Periods of prolonged plant-wetness.
Young plants usually begin to rot at soil level when they are 12-20 cm in height. Stems appear water-soaked, and the infection can be mistaken for a bacterial issue. Shoots wilt and fall over in a short period of time. Just above soil level, the stalk will be covered with a greyish fungal growth where conidia (fungal spores) are produced. Conidia are transported by wind, insects (attracted by rotting material), water splash and physical contact by staff to other leaves and buds. This causes further in leaf spotting and bud dieback. Small buds turn black and die. Larger buds turn brown and fail to produce a flower. If a plant is infected, most of the buds will more than likely fail.
Biology and lifecycle
Botrytis spp. are saprophytic (living on dead/decaying plant material) and parasitic (feeding off living material). First signs appear on the base of the stalks and the fungus over-winters on fallen plant debris. In the spring, as temperature increases ( Late March- early April) conidia form and spread to young, soft plant tissues. As the disease progresses, a gray-mold develops. The gray mold is made up of spores that are either wind-blown, splashed or transported by insects or touch by hands or tools onto new plants.
Prevent infection: Plant debris should be removed often destroyed, not composted. Wash hands after contact with infection. Spray tools periodically with a weak bleach solution (2%) or 70% ethanol solution. (Shop-bought bleaches are usually 5% in strength (check label), so dilute 1:2.5 i.e. 1 liter 5% sodium hypochlorite plus 1.5 liters water = 2.5 liters of 2% sodium hypochlorite)
Soil drainage: Peonies in well-drained soil have a reduced risk of botrytis formation. Do not overwater.
Location: Increased air circulation reduces disease risk. Space plants as widely as possible (2-3 feet is optimal but may not be practical in some situations). If possible, remove aging leaves from plants.
Use disease-free roots: If propagating, only take divisions only from healthy, disease-free plants.
Fungicide: Stem and bud Botrytis is the main disease issue and a programme for control will have to be implemented from emergence in the spring. The programme should be maintained throughout the growing season through harvest and should extend out to early Autumn. Rovral WG and Switch are systemic fungicides which have full label recommendations and can be used in a programme with protectants such as Amistar and Signum which have off label approval. Fungicides must be applied in advance of the disease as a protectant.
Quick video of disease check on Parlsey
Septoria on Parsley (mp4 video)