Fungal

Onion Smut

A soil-borne fungal disease that infects onion and leek seedlings in cool wet conditions, causing dark streaks on cotyledons and leaves and plant death.

Symptoms to Look For

Dark olive-green to black streaks inside young leaves visible when split open
Thickened, distorted leaves with dark powdery smut pustules
Seedlings dying before or shortly after emergence in infested soil

Affected Plants

OnionLeekShallotGarlic

Organic Solutions

Grow indoors and transplant

Start seeds in clean sterile compost indoors - seedlings more than 3 cm tall at transplanting have largely passed the susceptible growth window.

Trichoderma biocontrol

Apply Trichoderma-based soil inoculant to the seed row at sowing to establish beneficial fungi that compete with the smut pathogen.

Prevention

Rotate alliums to a new bed every 3 - 4 years as spores persist in soil for many years
Avoid sowing into cold, wet, compacted soil - wait until conditions improve or sow under cover

Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals - ever.