Crops Affected: potatoes, cruciferous vegetables (cabbage, etc.) greenhouse vegetables, etc (depending on the disorder)
Disease Cycle:
>Caused by differences between daytime soil temperature and moisture levels and night-time temperature and moisture levels
- Days with warm, wet soil followed by cool and saturated night-time air
>Water uptake by the roots is rapid and exceeds the rate of transpiration
- Cells under the surface of the leaves are stimulated to enlarge and divide, creating enough pressure to rupture the surface layers of leaf tissue
- Injury to the epidermal layers by blowing sand or feeding insects (e.g. thrips) can increase the problem
>In greenhouse situations, poor ventilation can slow transpiration while root pressure remains high
Symptoms:
>On cabbage, small, wart-like growths or bumps that develop in varying densities on the either interior or exterior surfaces of several of the outer leaf layers of cabbage
- May grow together – irregularly shaped elevated areas
- Growths may split and turn whitish – creates a crystalline appearance (initially)
- Turn brown and corky
>In greenhouse crops (tomato), leaf tissues may become waterlogged, resulting in raised, blister-like growths on upper or lower leaf surfaces; fruit may also develop edema
Management:
- Avoid over-irrigation when day and night temperatures differ greatly
- Ventilate greenhouses properly and regulate watering in situations when humidity may build up
Source : Alberta agriculture and forestry