Fungicides for narcissus disease management

As the mainstay of disease prevention, it’s important to have a good understanding of fungicides and the programmes for using them to best effect.

The information was last updated in 2016.

Fungicide products

Field trials on the use of fungicides for management of smoulder and white mould were conducted in 1998–2002 (BOF 041) and 2012–2013 (BOF 072 and 072a).

The results of these trials provide useful guidance on product selection and treatment timing.

However, some of the products found effective then are no longer permitted for use on narcissus. With leaf scorch, no fungicide efficacy trials have been conducted for over 30 years.

There is a limited set of fungicides currently permitted on narcissus, so it is therefore necessary to consider products with activity against fungi closely related to the target pathogens. It is also worth considering products from the same fungicide groups as those previously found effective on smoulder or white mould (that are no longer permitted), in order to provide options to construct a sustainable spray programme.

You must ensure any products you use are approved for use on narcissus before applying them to your crop - please check with your professional supplier, BASIS registered advisor or CRD.

Activity

Fungicides shown to have activity against a particular disease by field trials or other experiments are distinguished from those considered likely to have activity.

Growers report that applications against white mould and smoulder typically offer additional control of leaf scorch.

For all three diseases, there are several fungicide products available, from different fungicide groups, which are active or likely active against the target pathogens.

Note that many products are restricted to a maximum of two spray applications per crop, and some to just one.

Galantamine

Where narcissus is grown for galantamine production, some additional fungicides are permitted.

In research projects BOF 041, 072 and 072a, fungicides were used at their label recommended rate in order to provide a fair evaluation and to check for possible phytotoxicity to narcissus.

It may not be necessary to use products at their maximum label rate for the same beneficial effects.

The efficacy of mixtures of two or more fungicides each applied at a reduced rate on management of narcissus foliar diseases has not been examined in trials work.

Getting the timing right

Studies in the research project BOF 41 on control of smoulder and white mould found that:

• Bulb yield increase was greater with sprays applied both during emergence and around flowering (four sprays in total).
• Programmes consisting of just two sprays, focused either during emergence or around flowering or after flowering, gave little control of smoulder and a relatively small increase in bulb yield.
• For white mould, spray programmes commencing before first symptoms appeared were usually more effective than those commencing at or after, the appearance of first symptoms.
• For white mould, the number of sprays required to achieve effective control ranged from three to six depending on products used and the season.

Studies in the research projects BOF 72 and 72a found that:

• When three fungicide sprays were applied from immediately after the end of flowering, there was little benefit in applying sprays before flower harvest.
• This strategy would not be appropriate where disease becomes obvious before flower harvest or for areas where there is a history of early foliar disease.
• In a crop of cv. Early Flame, fungicide treatments that gave good control of foliar disease and delayed leaf dieback also increased flower yield the following year.
• Compared with untreated crop, flower yield was increased by Signum (44%), Tracker (27%) and Vivid (22%).

(Please note that registration for the use of Tracker (epoxiconazole) as a ground spray for narcissus has now expired.)

Spray programmes

When developing your spray programme it is worth noting:

• Numerous other programmes could be devised using these and other products.
• Cultivar susceptibility, crop age, disease occurrence in a crop and forecast weather should also be used to inform product choice and spray timing.
• The interval between sprays will be determined by interval since last treatment, disease pressure and opportunities to spray.
• Where early lifting or an autumn herbicide treatment is required, it would be prudent not to apply a late spray of a fungicide that delays leaf dieback.
• Signum is suggested for use pre-flowering because it has an EAMU for use on outdoor ornamentals and no stated harvest interval; any stated harvest interval on a label applies to flower harvest as well as bulb harvest
• Leaf scorch, smoulder and white mould all tend to increase in severity the longer a crop is down
• Crops intended to be left down for many years for flower production should be checked carefully for foliar diseases each year.
• Levels of smoulder are generally low in a first-year-down crop, but fungicide treatment around and after flowering can reduce the risk of a high incidence of smoulder primaries the following season.
• However, severe white mould can occur even in a first-year-down crop, especially where the crop is downwind of other narcissus crops affected by the disease.

Avoiding fungicide resistance

There are no published reports of fungicide resistance in either B. narcissicola or R. vallisumbrosae.

However, field trials on white mould control suggest that some strobilurin fungicides have become less effective in recent years than when they were first used.

To preserve the effectiveness of fungicides, growers should follow the guidelines outlined in the Fungicide Resistance Action Group technical leaflet: Fungicide resistance.

The main points to consider are:

• Devise a programme using fungicides from two or more different fungicide groups.
• Alternate products based on their chemical group or use two fungicides from different groups in mixtures, where both fungicides are active against the target fungus.
• Make full use of multi-site protectant fungicides, as these tend to be less prone to resistance development.
• Recent work on fungal foliar diseases on cereals indicates that use of mixtures of several fungicides, each at a reduced dose, is more beneficial in reducing selection of resistant strains than use of a single fungicide at full dose.

More information

BOF 072 – Narcissus: evaluation of fungicides for improved control of smoulder and white mould.

BOF 072a – Narcissus: improved control of foliar diseases and the effect of fungicide sprays on flower production.

BOF 076 and 076a– Understanding the physiological disorders in daffodil.

Factsheet 01/13: Practical measures to prevent and manage insecticide, fungicide and herbicide resistance for horticultural crops.

Please note this information was last updates in 2016. The majority of the content and recommendations remain pertinent to commercial Narcissus production, but some of the biocidal and plant protection products mentioned may no longer be approved for use on narcissus.

Biocidal and plant protection products must only be used in accordance with the authorised conditions of use. Regular changes occur in the authorisation status of biocides and plant protection products. For the most up to date information, please check with your professional supplier, BASIS registered adviser or the Chemical Regulation Division (CRD) of HSE (https://www.hse.gov.uk/crd/) before use.

While the Agriculture and Horticulture Development Board seeks to ensure that the information outlined on this page is accurate at the time of publishing, no warranty is given in respect thereof and, to the maximum extent permitted by law the Agriculture and Horticulture Development Board accepts no liability for loss, damage or injury howsoever caused (including that caused by negligence) or suffered directly or indirectly in relation to information and opinions contained in or omitted from this information.