Gadenin日本語Get the appNarcissus bulb fly hollows the bulb out
This is the serious one. The adult is a stout, hairy, bee-like fly that flies low over the ground on warm, still days in late spring and early summer, at exactly the time daffodil foliage is collapsing. It lays eggs at the neck of the bulb or in the soil crack left where the leaves went down. A single grub burrows to the basal plate and spends the rest of the year eating the inside of the bulb.
You see nothing that year. The following spring the clump produces a few thin, grassy leaves and no flower, or nothing at all. Dig up the bulb and it is light, soft at the base, and full of a foul-smelling brown mush with one fat cream-colored grub in it. That is the diagnosis; there is no treatment at that point and the bulb goes in the bin.
Prevention is cultural and it works. Firm the soil down over the neck of the bulb after the foliage dies back, filling the hole the leaves leave behind, so there is no easy route in. Rake soil over naturalised clumps in grass for the same reason. The fly prefers warm, sunny, open, well-drained sites, so daffodils in light shade or in grass are attacked far less than the same bulbs in a hot open border. Covering high-value clumps with row cover through the flight period excludes the fly entirely, though it is only practical over a small area.
Above all, do not plant a bulb that feels light or soft, and do not put a suspect bulb back in the ground to see what happens. A clump left in place because you were not sure feeds the next generation of flies.
Basal rot works up from the bottom
Basal rot is a soil-borne fusarium that enters through the basal plate. In the ground it shows as a clump that comes up weakly, yellows early and then simply stops appearing. In storage it shows as bulbs that go soft, develop a chocolate-brown discoloration spreading up from the base, and sometimes carry a pinkish-white fungal growth on the plate itself.
It is driven by warmth and moisture at the wrong time. Bulbs lifted and stored warm, beds that stay wet through summer, and high-nitrogen feeding all increase it. Damage from a spade or a careless division gives it an entry point, which is why clean handling at lifting matters.
There is no cure for an infected bulb. Discard it, discard obviously affected neighbors, and do not compost any of it. The fungus persists in the soil, so do not replant daffodils in that exact spot; move the planting elsewhere and give the ground several years. Lifting during dry weather, handling gently and storing cool and airy is the whole of the prevention.
What you are looking at, and what to do
Most daffodil problems present as one of a small number of symptoms, and the useful skill is telling a treatable nuisance from a bulb that has to be destroyed. Work through the symptom first and only then decide.
| What you see | Likely cause | What to do |
|---|---|---|
| A few thin grassy leaves, no flower, one clump only | Narcissus bulb fly grub inside the bulb | Lift and squeeze; if soft, destroy it |
| Plenty of healthy leaves, no flowers, whole clump | Congestion, shallow planting or shade | Lift and divide in dormancy, replant deep |
| Bulb soft with brown rot spreading up from the base | Basal rot | Destroy, do not compost, replant elsewhere |
| Small pale swellings felt along the leaf, leaves distorted | Stem and bulb eelworm | Destroy the clump and the soil around it |
| Pale streaks or mottling along the leaves, weak flowers | Virus, spread by aphids | Destroy affected plants, control aphids |
| Brown, water-soaked spots on leaves and flowers in wet spring | Fungal leaf scorch or botrytis | Remove affected foliage, improve airflow |
| Ragged holes in petals, slime trails | Slugs and snails | Cosmetic only, no action needed for the bulb |
Stem and bulb eelworm is the one to be ruthless about
Stem and bulb eelworm is a microscopic nematode and the most contagious daffodil problem. The early sign is small, pale, slightly raised swellings you can feel by running a leaf between finger and thumb, often before you can see anything. Later the foliage is distorted and stunted and the plant collapses. Cut an infected bulb across and it shows concentric brown rings in the tissue.
There is no home treatment. Lift and destroy the affected clump along with a generous margin of the surrounding soil, and do not compost any of it. Clean tools and boots afterwards, because the nematode spreads on soil carried around the garden. Do not plant narcissus, and preferably no bulbs at all, in that ground for several years.
The reason for the severity is that eelworm spreads slowly and invisibly at first. A clump left in place because it looked only slightly off is how a localised problem becomes a garden-wide one over three or four seasons.
The problems daffodils do not have, and what to record
Every part of a daffodil is toxic, and this rules out a whole category of trouble. Squirrels, mice and voles do not dig up the bulbs. Deer and rabbits do not eat the foliage or flowers. You need no netting at planting time and no fencing afterwards, which is the main practical reason to choose daffodils over tulips in an exposed or rural garden. The same toxicity means gloves when handling large numbers of bulbs, and keeping cut stems away from pets.
Aphids on the flower stems in a mild spring are worth dealing with, not because the aphids themselves do much damage but because they transmit the viruses that cause streaked foliage and steady decline. A jet of water or squashing them by hand is usually enough at the scale a garden clump presents.
Keep a note of every bulb you discard, with the reason and the location. Bulb fly damage in particular is a slow build: one hollowed bulb this year and four next year in the same sunny border is a pattern that tells you to firm the soil or row cover that bed, whereas a single loss recorded nowhere just looks like bad luck. Note also the date you first saw the adult flies over the bed, because that is when your cover or soil-firming needs to be in place next year.