Cabbage

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.

Plasmodiophora brassicae

A severe soil-borne disease causing grotesque swelling and distortion of brassica roots. Infected plants cannot take up water or nutrients effectively and typically collapse or die back. Spores survive in soil for up to 20 years. One of the most serious diseases affecting the brassica family.

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.

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.