Bolting
Spinach is a fast-growing annual prone to bolting. Bolting is when a vegetable crop runs to seed. Spinach is a long-day plant, so initiates flowering when day length increases, making it natural for spring-sown plants to run to seed in summer. Good, moist growing conditions give rapid growth and harvestable leaves before flowering. Successional sowing helps achieve a constant supply, while sowing after midsummer avoids the problem. Bolt-resistant cultivars include ‘Monnopa’, ‘Palco’ and ‘Spokane’ (all three have AGMs), while ‘Palco’ and ‘Spokane’ are also mildew resistant.
Spinach blight
This is caused by cucumber mosaic virus. Early symptoms are yellowing of younger leaves and later the older ones, which die, leaving a few distorted central leaves. Burn infected plants and control aphids, which spread the disease.
Leaf spot
A fungal infection (Cladosporium variabile) can cause circular, light-brown or grey areas with brown or purple edges. Remove infected leaves. A new site each year, applying 10g per sq m of potassium sulphate, and thinning rows early all help.
Downy mildew
Peronospora farinosa f. sp. spinaciae produces grey mould on leaf undersides and yellow blotches on the upper. Affect-ed tissue dies and dries out. Removing infected leaves and thinning rows to improve airflow can reduce problems.