Pests and Diseases of Bulbs, Corms and Tubers
Bulbs, Corms and Tubers
Basal rot (Fusarium oxysporum and others)
Typical symptoms: Bulbs rot in the ground, particularly after a hot summer, and leaves fail to emerge the following year. This is one of the most serious narcissus diseases.
Prevention and treatment: Grow resistant nar- cissus cultivars where this disease is a problem; the Triandrus, Jonquil and Tazetta groups are highly resistant. Lift others in early summer before thegets hot, when the disease is most active. Where symptoms are seen, lift all bulbs and destroy any that feel soft around the base. Check the bulbs again after a month in store. Replant healthy bulbs on a new site.
Large narcissus fly (Merodon equestris)
Narcissi, bluebells and hyacinths are affected.
Typical symptoms: In early to mid-summer this fly lays its eggs in the soil near the necks of bulbs. The developing large brownish larvae eat their way into bulbs which, next season, will produce narrow, yellow and distorted leaves and fail to flower. Bulbs in open sunny places are most prone to attack.
Prevention and treatment: Deter the fly from laying its eggs by raking soil or mulch over the holes left as the leaves die down. Alternatively, cover bulbs in sunny places with horticultural fleece while the leaves die down. Replant healthy bulbs in a shady spot.
Stem eelworm (Ditylenchus dipsaci)
Stem eelworm affects narcissi, tulips, hyacinths, scil las and snowdrops; also some herbaceous plants, vegetables and.
Typical symptoms: Infested bulbs feel soft and produce distorted leaves and. Flowers may fail to appear.
Prevention and treatment: Destroy soft, discoloured bulbs and infected plant debris, as well as healthy-looking bulbs within a 1m (31/2ft) radius. Do not grow susceptible plants on the site for two or three years (see Onion Pests and Diseases).
Vine weevil (Otiorhynchus sulcatus)
Cyclamen, begonias and many other plants are susceptible to this pest.
Typical symptoms: Plants wilt suddenly and do not recover after watering. Those in pots are particularly susceptible.
Prevention and treatment: See General Garden Pests
White rot (Sclerotium cepivorum)
White rot affects ornamental alliums.
Typical symptoms: A white fluffy mould is visible on bulbs, which rot and die.
Prevention and treatment: Destroy infected bulbs; do not grow alliums in the same area again. See Onion Pests and Diseases