Narcissus and Daffodil

60 G.R. Hanks
Following planting in late-summer or autumn, root outgrowth is rapid, and shoot
growth continues inside the bulb until slowed by falling temperatures. Except for
Tazetta narcissus, the plants have a cold requirement for rapid, synchronous shoot
growth and anthesis, and, once this requirement has been met by normal winter
temperatures, shoots grow at a rate determined by ambient temperatures. Bulb
growth is rapid from around the time of anthesis, but is soon curtailed by the
prompt onset of foliar senescence in summer, perhaps as a means of conserving
water. In the UK, initiation of the flower begins in May and its differentiation is
completed in July or August. Further details of the annual pattern of narcissus
growth are given in Chapter 1 of this volume.
PESTS, DISEASES AND DISORDERS
In the commercial production of narcissus bulbs, considerable effort is needed to
control pests and diseases. As for other crops, pesticide applications in the field are
important, but bulbs also present a convenient opportunity for pesticide applications
during the ‘dormant’ stage between bulb lifting and re-planting. Many pests
and diseases are exacerbated by the techniques of modern husbandry, such as
high planting densities, reduced sorting of bulbs by hand, bulk handling and
two-year-down growing (Price, 1977a,b), but, since it would be uneconomic to
change these practices, control measures have to be highly effective to work under
these exacting conditions.
Methods of control (or management) of narcissus pests and diseases, and for
preventing physiological disorders, are incorporated into the following description
of narcissus bulb production. Further descriptions and methods of control of
pests, diseases and disorders are available in a number of texts. For the UK, information
on pests is given in Lane (1984), on diseases and disorders in Moore et al.
(1979) and ADAS (1986a), and generally in Rees (1972, 1992), Linfield and Cole
(1989), Hanks (1993) and Linfield (1994). Dutch information includes Bergman
et al. (1978) and Langeslag (1990), and US information includes Gould and Byther
(1979) and Chastagner and Byther (1985).
Narcissus bulbs are unusual in that the major pest, stem nematode (‘eelworm’,
Ditylenchus dipsaci), is controlled by immersing bulbs in a hot-water treatment
(HWT). Other pests are also controlled by HWT, including the larvae of large
narcissus fly (Merodon equestris), small narcissus flies (Eumerus strigatus and E. tuberculatus),
other nematodes, narcissus leaf miner (Norellia spinipes), bulb scale mite
(Steneotarsonemus laticeps) and bulb mites (Rhizoglyphus and Histiostoma species). Of
these, the large narcissus fly and bulb scale mite are the most significant pests,
while small narcissus flies and bulb mites attack only damaged bulbs. Besides
D. dipsaci, other nematode pests include the narcissus bulb and leaf nematode
(Aphelenchoides subtenuis) and the root-lesion nematode Pratylenchus penetrans that
can attack bulbs causing a root rot in conjunction with the fungus Nectria radicicola.
Nematodes transmitting narcissus viruses are Trichodorus and Paratrichodorus spp.
(transmitting tobacco rattle virus), Longidorus spp. (tomato black ring and raspberry
ringspot viruses) and Xiphinema diversicaudatum (arabis mosaic and strawberry
latent ringspot viruses). Potato cyst nematode (PCN, Globodera spp.) does not
attack narcissus bulbs, but its presence may cause the rejection of bulbs for export