Narcissus and Daffodil

Production of Narcissus bulbs 61
to some countries. Slugs attack bulbs and flowers, and the garden swift moth
(Hepialus lupulinus) is an occasional pest. Aphids do not usually colonise narcissus,
but several common species spread viruses through exploratory probings. Vertebrate
pests are not usually troublesome in narcissus growing.
Narcissus fungal diseases include bulb rots and foliar diseases, of which the most
significant is base rot (basal rot) caused by Fusarium oxysporum f.sp. narcissi. Many of
the procedures in narcissus growing are designed to control base rot, although
incidentally helping to control other fungal pathogens. The control of base rot
involves a range of measures, of which the use of fungicides is only one (Melville,
1980; Tompsett, 1980a; ADAS, 1989b). Some of the most widely grown narcissus
cultivars, such as ‘Golden Harvest’ and ‘Carlton’, are susceptible to base rot. Apart
from base rot (Tompsett, 1986), relatively little is known of varietal differences in
susceptibility to other diseases and pests, although Beaumont (1950) gave some
useful information. Neck rot is related to base rot, and is also generally caused by
F. oxysporum f.sp. narcissi, although Penicillium hirsutum and Botrytis narcissicola are
also implicated (Davies et al., 1998; Carder, 1999). Although reported by Hawker
in 1935, neck rot has caused concern recently as it is seen in pre-export inspections,
and it attacks a wider range of cultivars than base rot (Davies et al., 1998).
It is important to distinguish pathological neck rot, which is a rot clearly spreading
down from the bulb neck, from ‘physiological neck rot’, which is simply the
natural presence of the dead bases of leaves in the bulb neck. Less usual, or less
serious, fungal rots include grey bulb rot (Rhizoctonia tuliparum), soft rot (Rhizopus
spp.), Penicillium rots, black slime (Sclerotinia bulborum) and white root rot (Rosellinia
necatrix). The major fungal foliar diseases are smoulder (Botrytis narcissicola),
fire (Sclerotinia polyblastis), leaf scorch (Stagonospora curtisii) and white mould (Ramularia
vallisumbrosae). A number of fungi attacks narcissus bulbs resulting in skin
diseases that give a downgraded appearance, with darker, greasy, multi-layered or
irregular skins (Bergman et al., 1978).
Bacterial diseases are not generally associated with narcissus. Although mycoplasma-like
organisms have been reported in unhealthy narcissus plants (Bellardi
et al., 1990), there is no information as to the wider significance of this discovery. On
the other hand, some 21 viruses are known to infect narcissus, of which about 13 are
considered to be of economic importance, especially the aphid-borne narcissus
yellow stripe, narcissus late seasons yellows and narcissus white (or silver) streak
viruses (Brunt, 1995). Most have aphid or nematode vectors, although for some the
vector is not known or mechanical transmission has been demonstrated. Aphid- and
nematode-borne viruses are unlikely to be spread by handling healthy and infected
plants alternately, and Mowat (1980a) found no evidence for the mechanical transmission
of narcissus tip necrosis virus by handling and flower cropping. However,
narcissus mosaic virus is easily spread by mechanical inoculation (Brunt, 1966) and
can be spread by flailing (Mowat, 1987). Only the ringspot viruses are seed-borne.
Most narcissus stocks are heavily infested with viruses, and while their effects may be
generally less dramatic than those of stem nematode or base rot, they are important
and their significance should not be under-estimated by growers.
Narcissus crops may be affected by a number of physiological disorders, including
damage from frost, waterlogging and sun scorch. Damage due to chemical or
other treatment can be due to herbicides, HWT, formaldehyde or mechanical
damage. ‘Grassiness’ (‘horses teeth’) can result when the main shoot of a bulb is