Narcissus and Daffodil

Production of Narcissus bulbs 87
being formed at this time and may be sensitive to damage by herbicides; trials have
taken place on herbicides suitable for application immediately after the flower
cropping stage, before the crop foliage has spread to cover the furrows completely
(Briggs and Hanks, 1997).
Suitable herbicides are given in the standard texts and elsewhere (Mével, 1979;
ADAS, 1990a), and herbicide trials have been published in several countries (e.g.,
Turquand, 1968; BBLF, 1972; Briggs, 1972a,b; Lawson and Wiseman, 1976;
Ryan and MacNaeidhe, 1978; Rupasava et al., 1981; Rusalenko et al., 1981; Smith
and Treaster, 1982, 1984, 1989, 1990; Koster and Kruyer, 1983; Bing, 1985;
Skroch et al., 1988, 1994; Howard et al., 1990; al Khatib, 1996). Several types of
herbicide damage can occur, including leaf scorch and chlorosis, abnormalities
such as distorted flowers, damage to the basal leaf meristem resulting in flaccidity,
and reduced growth (Ivens, 1966). Cereal seed may be a problem where crops
have been covered with straw (Koster and de Rooy, 1981; Koster, 1983; Koster
and van der Meer, 1986). The control of cereal, potato and other ‘volunteers’
(plants left from previous crops) in narcissus crops may also prove difficult.
Fungicide sprays
It is usual to apply fungicide sprays to narcissus crops to control foliar diseases
such as smoulder, leaf scorch, fire and white mould, and this is more important
where bulbs are being grown on a two-year-down basis because of the build-up of
disease in bulbs, debris or soil. Spray programs are not always successful in controlling
these diseases (Melville, 1980), although they may help in the control of
pathogens involved in bulb rots (Davies et al., 1998). A general effect of fungicides,
especially if a programme of sprays is used, is to delay foliar senescence, probably
by controlling fungi that degrade the leaf cuticle (Rees, 1972; Jones, 1978). Since
bulbs are usually lifted before the leaves have died down, this has the disadvantage
that crops are even greener at lifting.
There is little specific information on the most effective fungicides or fungicide
programs for controlling particular diseases, and in the UK it is usual to
apply several fungicides with different modes of action, which also reduces the
likelihood of the development of resistance to fungicides. Typical fungicides
used in the UK and the Netherlands include chlorothalonil, iprodione, vinclozolin,
mancozeb, zineb/maneb, benomyl, carbendazim, thiophanate-methyl and
procymidone, sometimes involving tank-mixes. Spraying often begins soon after
shoot emergence, continuing at 7- to 10-day intervals until flowering, with one
or two further sprays after flowering to control infections resulting from the
damage of flower cropping (O’Neill and Mansfield, 1982; O’Neill et al., 1982). In
practice, it may be difficult to apply fungicides at target dates because of unsuitable
weather, a particular problem in wet and windy areas where suitable ‘spraying
days’ may be relatively few. In the year of lifting, the spray programme is
often curtailed to encourage the foliage to die down. At present, no detailed recommendations
are available about the critical times for spraying to take place
(Hanks and Briggs, 1999), but key times are thought to be when frost-damage
occurs, after flowering or cropping (because of the damage caused by cropping
or the presence of decaying flowers if not cropped), as well as in periods of damp
weather.