Magnesium deficiency (Mg)
Interveinal chlorosis on older lower leaves with a marbling effect (leaf veins remain green). Later various shades of red/purple can appear as chlorophyll breaks down leading eventually to leaf necrosis. Yield effect on determinate cultivars may be more severe.
Treatment: Foliar application of EPSO Top®, EPSO Microtop® or EPSO Combitop®. Use of soil fertilisers containing water-soluble Mg such as ESTA® Kieserit or Patentkali® is a very effective way of ensuring that deficiency is prevented.