Crop Walkers’ Guide

Narcissus Narcissus Crop Walkers’ Guide

Introduction

Narcissus growers can encounter a range of problems that can impact on both the quality and yield of flowers and bulbs unless they are identified and dealt with. Often, such problems are linked to pests and diseases, but a range of physiological and cultural disorders may also be encountered.

This AHDB Horticulture Crop Walkers’ Guide has been created to assist growers and agronomists in the vital task of monitoring crops in the fields and bulbs post-lifting. It is designed for use directly in the field to help with the accurate identification of pests, diseases and disorders of narcissus. Images of the key stages of each pest or pathogen, along with typical plant symptoms produced have been included, together with succinct bullet point comments to assist with identification.

As it is impossible to show all symptoms of every pest, disease or disorder, growers are advised to familiarise themselves with the range of symptoms that can be expressed and be aware of new problems that may occasionally arise. For other bulb and cut flower crops, see the AHDB Horticulture Cut Flower Crop Walkers’ Guide.

This guide does not attempt to offer advice on available control measures as these frequently change. Instead, having identified a particular pest, disease or disorder, growers should refer to other AHDB Horticulture publications which contain information on currently available control measures.

Nathalie Key Knowledge Exchange Manager (Narcissus) AHDB Horticulture

Introduction 1 Narcissus Crop Walkers’ Guide

Contents

Section 1 – Pests SECTION 1

Aphids 1.1 Caterpillars 1.2 Mites, bulb 1.3 Mite, bulb-scale 1.4 Narcissus fly, small 1.5 Narcissus fly, large 1.6 Nematodes, root lesion (and others) 1.7 Nematodes, stem (and bulb) 1.8 Slugs and snails 1.9

Diseases SECTION 2

BACTERIAL Soft rot 2.1

FUNGAL Basal rot 2.2 Fire 2.3 Leaf scorch 2.4 Neck rot 2.5 Penicillium bulb rot 2.6 Smoulder 2.7 White mould 2.8

VIRAL Viruses (common leaf symptoms) 2.9 Viruses (other symptoms) 2.10

2 Contents Cultural disorders SECTION 3

Chocolate spot 3.1 Daffodil rust 3.2 Flowering disorders 3.3 Frost damage 3.4 Hail and other damage 3.5 Herbicide damage 3.6 Hot-water treatment damage 3.7 Hot-water treatment damage 3.8 Mechanical damage 3.9

References SECTION 4

Acknowledgements 4.1 Photographic credits 4.2 Photographic credits 4.3

Contents 3 Pests Narcissus Crop Walkers’ Guide SECTION 1

1 Pests Aphids

Aulacorthum solani, Macrosiphum euphorbiae, etc.

• Multiple aphid species affect • Antennae length and shape Narcissus – Aulacorthum solani, and colour of siphunculi (tubes Macrosiphum euphorbiae, Myzus extending from rear of the body) persicae etc. are used for species identification. • Aphids are small (around 2 mm • Migrating winged aphids rarely in length) and pear-shaped, they feed on narcissus, though several are found on the underside of common species may spread leaves and in the growing points virus through exploratory probing. of plants.

Pests 1.1 Caterpillars

Korscheltellus lupulina, Hepialus humuli and other species

• Adult female ghost swift moths • Caterpillars of common swift (H. humuli) (bottom left image) moth, which emerge from eggs tend to be small (40–70 mm dropped in flight, can make large wingspan), brown or yellow and holes in the sides and bases of inconspicuous (the male ghost daffodil bulbs. swift moth has white forewings). • Caterpillars of the ghost swift Caterpillars develop to 40–50 mm moth, are also an occasional pest. in length, with a translucent body and a brown head (top left image). • Caterpillars of other moths found feeding on flower buds (bottom • The common or garden swift right image) probably occur moth (K. lupulina) (top right image) opportunistically. can be a pest of daffodils.

1.2 Pests Mites, bulb

Rhizoglyphus and Histiostoma species

• Bulb mites are pale in colour and • Generally, bulb mites occur in have two dark spots. They are large numbers as secondary clearly visible to the naked eye, pests on damaged bulbs and being much larger (up to 0.9 mm are often associated with fungi in in length) than the bulb-scale mite damaged, musty bulbs. Mites can (0.2 mm). also penetrate bulbs and become established internally.

Pests 1.3 Mite, bulb-scale

Steneotarsonemus laticeps

• The bulb-scale mite is • Feeding produces leaves that light-coloured and only just visible are shinier than normal and with to the naked eye. They usually saw-tooth marginal marks (top occur in the top third of the right image). Dark feeding marks bulb, mainly in the neck region, are produced within the bulb and attacking the new shoots as can be seen when the bulb is cut the weather warms. transversely or lengthways. • The pest occurs sporadically in the field, however it multiplies rapidly on protected crops.

1.4 Pests Narcissus fly, small

Eumerus strigatus and E. tuberculatus

• Adults are around 6 mm in • Unlike large narcissus fly, larvae length and less ‘bumblebee-like’ occur in groups within the bulb in appearance than the large and two or three generations can narcissus fly. Eggs are around occur per year. They can pupate 0.8 mm in length and pupae in storage; cocoons can be found are 6 mm long. in bulb stores and on containers. • Adults lay eggs only on damaged • Generally a minor pest, but its or weak bulbs. presence is a good indication of a need to improve bulb husbandry.

Pests 1.5 Narcissus fly, large

Merodon equestris

• Adults are hoverflies resembling • Larvae always occur singly within small bumblebees (around 12 mm bulbs. It eats away the centre in length). They emerge from the of the bulb leaving a mass of soil during May/June and become granular debris and can reach active when temperatures are 18 mm in length by the autumn. above 20°C. The pest pupates in the soil. • Eggs are laid on the foliage close • Commercially significant and can to the soil and the larvae crawl cause substantial losses in warm down and enter the bulb in early summers in South West England. summer via the base plate (one Also occurs in eastern England. generation per year).

1.6 Pests Nematodes, root lesion (and others)

Pratylenchus penetrans, Aphelenchoides subtenuis, etc.

• Root lesion nematodes are • Root lesion nematodes mostly microscopic (0.8 mm in length) occur on the Isles of Scilly where and their feeding damages roots clean land for bulb production is allowing the fungus Cylindrocarpon scarce, exacerbated by destructans to enter through multi-year growing. wounds. Typical symptoms include • Other nematode species are virus weak and rotting roots, stunted vectors. Potato cyst nematode plants and gaps within crops. does not attack daffodils, but • Narcissus bulb and leaf nematode bulbs for sale must be clean to and associated rots occur rarely on ensure it is not carried. the Isles of Scilly, with similar effects.

Pests 1.7 Nematodes, stem (and bulb)

Ditylenchus dipsaci

• Nematodes are microscopic • Cutting bulbs transversely reveals translucent worms (previously brown rings (top right image). referred to as eelworms) about Off-white blobs of ‘wool’ may 1–2 mm in length. exude from the base plate that can survive for over 10 years (bottom • Bulb infestation leads to patches left image). of poor crop growth in the field. Other symptoms include • EU quarantine pest and universal characteristic yellow ‘spikkels’ threat to daffodil growing. on leaf margins and stem keels.

1.8 Pests Slugs and snails

Arion hortensis, Deroceras reticulatum, etc. and Helix species

• The field and garden slugs are • Slugs cause extensive damage the most common and damaging to daffodils above and below species. The field slug is light ground, especially in mild, brown in colour and 3–4 cm in damp weather and on heavy length (top left image), the garden soils. Coronas of some varieties slug is grey or black and grows up are prone to attack by slugs. to 4 cm. Slugs are now recognised as a significant pest of daffodils. • A number of snail species can graze widely on stems, leaves, buds and flowers.

Pests 1.9 Diseases Narcissus Crop Walkers’ Guide BACTERIAL SECTION 2 FUNGAL VIRAL

2 Diseases BACTERIAL Soft rot

Rhizopus species

• Affects bulbs stored at high • Bulbs rot quickly to mushy, humidity and temperature (above grey-white mass covered with 80% RH and 30°C). The disease coarse mycelium (top left image). can occur during warm storage, • Not often seen now, but Rhizopus in non-temperature-controlled soft rot can develop quickly under transport and during poor storage conditions. propagation (‘chipping’).

Diseases – Bacterial 2.1 FUNGAL Basal rot

Fusarium oxysporum f. sp. narcissi

• Bulb foliage may die down • If the bulb is cut lengthways, a prematurely in affected plants moist chocolate-brown rot can be (top left image). On lifting, bulbs seen spreading upwards from the may feel soft or may already be basal plate (bottom right image). completely rotted or dried out • Cultivars differ in susceptibility: (bottom left image). some popular cultivars are highly • White or pink fungal growth susceptible; some resistant ones may be visible externally on seem able to lose their resistance. the base (top right image). Basal rot can cause major losses in storage. The disease develops rapidly at 20–30°C.

2.2 Diseases – Fungal FUNGAL Fire

Sclerotinia polyblastis

• Initially causes water-soaked • Prevalent under mild, humid spots on flowers, spots turning conditions such as those in brown with visible sporulation. South West England. Affects Spores infect leaves (often near Tazetta (and to a lesser extent, tips) giving small, elliptical, mainstream) cultivars. pale-brown spots, later accompanied by yellow streaking up and down leaf (bottom image). • Dieback can occur in three to six weeks. Sclerotia (around 1 cm in length) overwinter in soil and debris (but not in bulbs).

Diseases – Fungal 2.3 FUNGAL Leaf scorch

Stagonospora curtisii

• Emerging leaves develop reddish, • Lesions produce minute yellowish or brownish tips pycnidia (0.2 mm in diameter). separated from healthy tissue by Stems and flowers become yellowish zones. Lesions spread spotted with infections during down in damp weather cut-flower storage. forming eyespots. • Widespread on daffodils under • Secondary lesions are initially suitable conditions. Damaging water-soaked spots, turning in South West England. The scabby and coalescing. The pathogen persists in bulb and pathogen leads to rapid dieback. on debris.

2.4 Diseases – Fungal FUNGAL Neck rot

Fusarium oxysporum f. sp. narcissi, etc.

• The principle pathogen is Fusarium • Where Penicillium is implicated, oxysporum f. sp. narcissi., but it may have ginger colouration other species that cause neck rot (top right image). include Botrytis narcissicola and • The disease should not be Penicillium hirsutum. confused with ‘physiological • The rot starts in the bulb neck, neck rot’, a natural dieback of being the same colour rot as leaf bases in the bulb neck that basal rot, but it progresses is dry and non-progressive downwards through the bulb (bottom right image). scales. Eventually, the pathogen invades the basal plate and destroys the new shoot.

Diseases – Fungal 2.5 FUNGAL Penicillium bulb rot

Penicillium species

• Commonly found on damaged • Under poor storage conditions, areas of bulbs after lifting, for aggressive strains develop example, where the scales have rapidly. Blistery markings appear been torn or offsets removed. externally, patches of grey-green Damage is often limited to the mould develop, leading to a outer bulb scale with patches of complete dark-brown bulb rot. grey-green mould externally • Penicillium is a particular problem (top left image). with dwarf cultivars (like • The bulb may be reduced to ‘Tête-à-Tête’) and during a ‘puffer’ (dried, rotted bulb propagation (‘chipping’). producing clouds of spores when broken).

2.6 Diseases – Fungal FUNGAL Smoulder

Botrytis narcissicola

• At emergence, infected shoots • Spore dispersal produces flower (‘primaries’) have crooked, torn, spotting (bottom left image). dark leaf tips that are stuck • Sclerotia (1.5 mm in diameter) can together and (if damp) covered in be found on and in the bulb and a grey spore mass. in the soil (bottom right image). • Leaves have dark lesions at tips • Common wherever daffodils are and margins, yellowing zoning grown. Probably exacts a modest can develop around the lesions but ongoing yield loss. and leaves become sickle-shaped (top image).

Diseases – Fungal 2.7 FUNGAL White mould

Ramularia vallisumbrosae

• Pale spots or streaks occur on • Causes severe epidemics in leaves and stems, with a warm, wet springs. Previously creamy-white spore layer associated with mild areas like developing under moist South West England, but now conditions. Lesions spread established in other areas. downwards and coalesce, producing rapid dieback and yield reductions. • Minute sclerotia (0.15 mm in diameter), form in leaves and overwinter on debris in soil (not in bulbs).

2.8 Diseases – Fungal VIRAL Viruses (common leaf symptoms)

Narcissus latent (NLV), etc.

• These four viruses are aphid-borne, leaf distortion early in the season, common and can cause early and flower breaking. Under warmer dieback and yield loss. Narcissus conditions, narcissus white streak latent virus (NLV) is symptomless virus (NWSV) causes green to or causes mild chlorosis (top left purple streaks, later white, yellowish image). Narcissus late season or grey (bottom right image). yellows virus (NLSYV) causes mild • Viruses are a serious underlying chlorotic streaking or mottling later threat. Most daffodil stocks are in the season (top right image). infested with viruses, often more Narcissus yellow stripe virus than one (a combination of viruses (NYSV) (bottom left image) causes may elicit or exacerbate symptoms). yellowish leaf streaks, mottling or

Diseases – Viral 2.9 VIRAL Viruses (other symptoms)

Narcissus mosaic (NMV) and yellow stripe viruses (NYSV) etc.

A C

B

• Narcissus mosaic virus (NMV) • Narcissus degeneration virus causes flower breaking (A and B; (NDV) gives rise to a chlorosis and C is normal). NMV also causes a general decline, while cucumber mild mosaic or brown, oval, late- mosaic virus (CMV) may be season leaf spots. symptomless or may cause a mosaic. • Narcissus yellow stripe virus (NYSV) also causes flower • Other viruses include: Tobacco breaking, while narcissus tip rattle virus (TRV), arabis mosaic necrosis virus (NTNV) may be virus (AMV), tomato black ringspot symptomless or may cause a (TBRSV) and raspberry ringspot late-season leaf-tip necrosis virus (RRSV). and dieback.

2.10 Diseases – Viral Narcissus Crop Walkers’ Guide SECTION 3 Cultural disorders Cultural disorders 3 Chocolate spot

• The only symptom of this disorder • Cause unknown, but not known is spots or small patches the to be attributed to a pathogen colour of dark chocolate on or nutritional issue. Sometimes leaves and stems. attributed to an effect of rising temperature. • A long-known physiological disorder, with usually little or no effect on cut flower quality, causing no significant losses.

Cultural disorders 3.1 Daffodil rust

• Symptoms are rust-coloured • Often unnoticeable, in some spots on stems and leaves, seasons and cultivars, from one small lesion to several disfigurement may be serious large clusters of lesions. In worst enough to downgrade stems or cases, symptoms also extend to make them unmarketable. transverse cracking and brittle • Cause unknown, but not stems (left image). apparently attributed to a • Rust has caused concern since pathogen or nutritional issue. the 1980s. Incidence varies considerably year-to-year and place-to-place.

3.2 Cultural disorders Flowering disorders

• Death of the flower bud in the • Flower bud death can also take spathe is common in Narcissus place at a much earlier stage, poeticus ‘Flore Pleno’ (top left visible when bulb is cut lengthwise image). Attributed to warm (bottom left image). growing conditions, poor rooting • When forced some cultivars, and adverse water relations. particularly ‘Carlton’, occasionally • A similar disorder is common produce flowers with notched in double cultivars, especially margins (bottom right image). ‘Golden Ducat’ (top right image). The cause is unknown. The spathe dries and dead buds resemble drumsticks.

Cultural disorders 3.3 Frost damage

• Cold damage near to or soon • A late frost near flowering leads after emergence can result in to the collapse of exposed stems yellow-tipping – chlorotic bands and leaves, either temporarily or across distal parts of leaves (top (if severe) permanently (bottom image). In extreme circumstances, image). Even if less severely it can result in dead leaf tips. affected, flowers may be distorted and fail to open normally.

3.4 Cultural disorders Hail and other damage

• Mild hail results in white flecking • Sun scorch (for example, during of the exposed surfaces of leaves windrowing) can damage the bulb (top left image). Severe hail scales, which become shrivelled can result in dead leaf tips (top and hard. right image) or even wholesale • In forced crops, a cool night withering and death of exposed followed by bright morning buds, stems and leaves sunshine can cause wilting and (bottom image). lodging, though the plants • Waterlogging can cause poor usually recover. growth, with yellow bands across the leaves.

Cultural disorders 3.5 Herbicide damage

• Apart from possible crop damage with hot-water treatment (HWT) through overdosing (for example, damage. Sulfonylurea residues at row ends, top left image), can cause similar distortion. several herbicides are known to • Clopyralid used to control be damaging to daffodils. thistles and volunteer potatoes • Diquat can damage the base can also damage daffodils. plate and bulb scales (top right Some recommended daffodil image). Glyphosate can cause herbicides (e.g. chlorpropham, ‘starry’ and otherwise distorted linuron) can cause reduced flowers (bottom images), daffodil growth if used under symptoms that could be confused inappropriate conditions.

3.6 Cultural disorders Hot-water treatment damage (mild)

• Hot-water treatment (HWT) • Above are symptoms of mild treads a knife-edge between too damage: leaf-tip mottling and mild a treatment (fails to control roughening, aborted flowers, nematodes adequately) and too petal and corona damage and harsh a treatment (kills nematodes small ‘starry’ flowers all due to but damages bulbs). Even when undertaking HWT too early. properly done, HWT will reduce crop growth and damage flowers and leaves to some extent, but normally this is offset by the benefits of nematode control.

Cultural disorders 3.7 Hot-water treatment damage (severe)

• More serious damage is shown • Damage to the stem apex may above. Damage to the roots and then result in ‘grassiness’ as base plate can result from late many offsets proliferate (bottom HWT (top left image). left image). • Severe leaf damage and death of the stem apex are caused by too harsh a HWT regime (top right image).

3.8 Cultural disorders Mechanical damage

• Damage to bulbs during handling and bottom left images) and is common. Impacts and dropping consequently the roots. can cause bruising several scales • Daffodil shoots and leaves suffer deep (top left image), though various breaks and lesions this does not generally lead through weather, predators and to secondary infection unless picking. Damage consisting of severely bruised bulbs are stored tears in the spathe and buds at high temperature and humidity. was formerly thought to result • Rough treatment at lifting and from removal of straw covering during cleaning can seriously materials (‘fork damage’, bottom damage the base plate (top right right image).

Cultural disorders 3.9 Narcissus Crop Walkers’ Guide SECTION 4 References References 4 Narcissus Crop Walkers’ Guide

Acknowledgements

AHDB Horticulture would like to thank Gordon Hanks, Independent Consultant for writing, sourcing images and advising on the production of this guide

Many thanks go to Rosemary Collier of the University of Warwick and Martin Stubbs, of the RHS for their assistance with identifying suitable images and to Adrian Fox of Fera for his guidance within the virus sections.

Thanks also go to everyone who contributed images and are acknowledged within the photographic credits section.

References 4.1 Narcissus Crop Walkers’ Guide

Photographic credits

Section 1 – Pests 1.1 (Top left, top right and bottom right) © InfluentialPoints, InfluentialPoints.com; (Bottom left) © ADAS 1.2 (Top left) © Ben Smart 1.2 (Top right) © Nigel Partridge, UK Moths; (Bottom left) © Ian Kimber, UK Moths; (Bottom right) © Gordon Hanks 1.3 (Left) © UK Crown copyright courtesy of Fera; (Top right) © Dr Janos Bodor; (Bottom right) © Ian Young and srgc.net 1.4 (Top left) © University of Warwick and predecessors; (Top right, bottom left and bottom right) © Gordon Hanks 1.5 (Top left) © Cheryl Moorehead, Bugwood.org; (Bottom left) © Stephen Cresswell; (Right) © W. Middlekauff and the UC Berkeley Department of Environmental Science Policy and Management 1.6 (All images) © University of Warwick and predecessors 1.7 (Top left) © UK Crown copyright courtesy of Fera; (Top right and bottom) © Andrew Tompsett 1.8 (Top left and bottom right) © University of Warwick and predecessors; (Top right and bottom left) © UK Crown Copyright courtesy of Fera 1.9 (Top left) © ADAS; (Top right, bottom left and bottom right) © Gordon Hanks

Section 2 – Diseases 2.1 (All photos) © University of Warwick and predecessors 2.2 (All photos) © University of Warwick and predecessors 2.3 (Top left and bottom) © UK Crown copyright courtesy of Fera; (Top right) © RHS Horticultural Science 2.4 (Whole page) © ADAS 2.5 (Top left, bottom left and bottom right) © University of Warwick and predecessors; (Top right) © RHS/Liz Beale 2.6 (Top left) © Gordon Hanks; (Top right and bottom) © University of Warwick and predecessors

4.2 References Narcissus Crop Walkers’ Guide

Photographic credits

2.7 (Top and bottom left) © Gordon Hanks; (Bottom right) © University of Warwick and predecessors 2.8 (Top left) © Gordon Hanks; (Top right) © University of Warwick and predecessors; (Bottom) © RHS Horticultural Science 2.9 (Top left) © UK Crown copyright courtesy of Fera; (Top right) © Gordon Hanks; (Bottom left and bottom right) © University of Warwick and predecessors 2.10 (All photos) © Hunter, DA et al. (2011)

Section 3 – Cultural disorders 3.1 (All photos) © Gordon Hanks 3.2 (All photos) © Gordon Hanks 3.3 (Top left, top right and bottom right) © University of Warwick and predecessors; (Bottom left) © Gordon Hanks 3.4 (Top) © University of Warwick and predecessors; (Bottom) © Gordon Hanks 3.5 (All photos) © Gordon Hanks 3.6 (All photos) © University of Warwick and predecessors 3.7 (Top left) © University of Warwick and predecessors; (Top right, bottom left and bottom right) © Gordon Hanks 3.8 (All photos) © University of Warwick and predecessors 3.9 (Top left, bottom left and bottom right) © University of Warwick and predecessors; (Top right) © Gordon Hanks

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