Lanarkshire disease

Lanarkshire disease is a fungal infection of strawberries caused by Phytophthora fragariae, the same oomycete responsible for redcore disease of the plant's roots. The infection manifests as a dry rot affecting the fruit itself rather than the crown or vascular tissue. Affected berries develop a firm, brown decay that typically starts at the calyx end and progresses inward, rendering the fruit unmarketable and inedible.

The disease occurs in cool, wet conditions typical of maritime climates and heavy clay soils. Phytophthora fragariae persists in soil water and spreads through splash from rain or irrigation. Spores enter fruit through the calyx or through small wounds. Once established in a field, the pathogen is difficult to eliminate because oospores can survive in soil for years. The infection rate increases sharply when plants are stressed by waterlogging or when fruit sits close to wet ground.

Geographic and historical context

The disease takes its name from Lanarkshire in Scotland, where it was first identified as a significant problem in commercial strawberry production. The region's cool temperatures and high rainfall created conditions particularly favorable for the pathogen. Although originally documented in Scotland, the disease has since appeared wherever Phytophthora fragariae-susceptible strawberry varieties are grown in damp climates, including parts of England and Northern Europe.

Management relies on cultural practices and variety selection. Improving drainage, avoiding overhead irrigation, and maintaining wider plant spacing reduce fruit contact with infected soil. Growing susceptible cultivars only in well-drained beds or containers minimizes risk. Some modern strawberry varieties bred for resistance to redcore also show tolerance to fruit rot, though complete immunity is uncommon. Chemical fungicide control of the fruit disease itself is limited; prevention through environmental management is more reliable than treatment once symptoms appear.