Spring Onion

Plants are drooping or losing vigour. Most commonly caused by water stress but can also indicate root damage, vascular disease, or heat scorch. Identifying the cause quickly is important as some causes are serious.

Seeds are emerging unevenly or not at all. Usually caused by soil temperature being too low, seeds sown too deep, poor seed-to-soil contact, or old seed stock.

Pythium spp. / Phytophthora spp.

Young seedlings collapse at or just below soil level, caused by fungal pathogens that thrive in overwatered, poorly ventilated growing conditions. Can spread rapidly through a seed tray.

Leaves are turning yellow, which can indicate a range of problems including nutrient deficiency, overwatering, disease, or natural senescence. Identifying whether the pattern is upper or lower leaves, whole leaves or between veins, is key to diagnosis.

Plants are significantly smaller or slower to develop than expected. May be caused by poor soil, nutrient deficiency, root restriction, compaction, pest damage to roots, or disease.

Bolting is the premature production of a flowering stem, triggered by temperature stress, day length, or drought. Once a plant bolts, leaf and root quality declines rapidly and the crop becomes bitter or tough. It is particularly common in early sowings exposed to cold followed by warmth.

Stromatinia cepivora

A highly persistent soil-borne fungal disease that attacks the roots and base of alliums. Sclerotia (resting bodies) survive in soil for 20+ years, making rotation largely ineffective once a plot is infected. Prevention is far more important than cure.

Small sap-sucking insects that colonise soft new growth, leaf undersides, and growing tips. Most species reproduce rapidly and colonies can establish quickly in spring and early summer. Also vectors of several plant viruses.

Soft-bodied molluscs that feed on plant material at soil level, most active at night and in wet conditions. A persistent pressure throughout the growing season, especially damaging to seedlings and young transplants.

General chewing damage from an unidentified pest, leaving holes or missing leaf sections. May be caused by caterpillars, beetles, or other insects. Inspect at dusk to identify the culprit.

General sap-feeding pest activity causing weakened or distorted growth. May be caused by aphids, whitefly, scale insects, or other sucking insects. Inspect leaf undersides and growing tips to identify the pest.