Fungi associated with, and possible causes of, neck rot of narcissus

Neck rot symptoms in post-harvest narcissus bulbs in the UK in the 1970s and 1990s were associated with Fusarium oxysporum, Botrytis narcissicola and Penicillium hirsutum. Their frequencies and the incidence of neck rot were similar in the studies in the two decades. On their own F. oxysporum, P. hirsutum and B. narcissicola were isolated from neck rots from only one, no and no stocks in the 1970s and from four, one and no stocks in the 1990s respectively. In most of the stocks, neck rot was associated with more than one of the three fungi. The most frequent combination in the 1970s was all three fungi and in the 1990s P. hirsutum with B. narcissicola. In the 1990s, F. oxysporum was found in 51% of stocks, being detected in rots extending to the bulb base and being responsible for the lack of shoot emergence. B narcissicola and P. hirsutum were found in 76% and 92% of stocks, respectively, and were isolated from rots of the neck, rots extending to the middle of the bulb and from completely rotted bulbs. A survey of crop husbandry practices in the 1990s revealed that only the presence of F. oxysporum was related to a stock problem. B. narcissicola was isolated in fewer bulbs from crops following cereals, crops treated with foliar sprays of dicarboximide fungicides and pre-store dip treatments of MBC (benzimidazole) or formaldehyde. There were fewer bulbs with P. hirsutum where bulbs had been planted at depths of 15 cm or less, following dicarboximide and MBC foliar treatments but more bulbs had P. hirsutum following bruising. These studies have shown that F. oxysporum is not the sole cause of narcissus neck rot; B. narcissicola and P. hirsutum are involved and these warrant further investigation.