In greenhouse production, interveinal chlorosis of the upper foliage is commonly associated with iron deficiency. Iron deficiency is initially commonly observed as a light-green coloration of the new upper foliage, progressing to more pronounced interveinal chlorosis, and finally, in severe cases, total yellowing and bleaching of the foliage. However, there is a wide range of causes for iron deficiency including insufficient iron fertility, high substrate pH, or overwatering. If only a few scattered plants are infected, then inspect the roots for root rot. While these can be common problems in greenhouse production, determining why iron deficiency is occurring is critical for attractive plants.
Pansies can be classified as high pH sensitive crops. A recent e-GRO alert highlights why in most cases, plants with abnormally high pH values will experience iron deficiency symptoms first. Iron is an immobile element in the plant and as a result, cannot be translocated from lower foliage to meet the plants’ needs in the newly developing portions of the plant. While interveinal chlorosis of the upper is commonly attributed to iron deficiency, less common similar symptoms may be observed with manganese (Mn) deficiency. Foliar tissue analysis should be used to determine if the observed symptoms are caused by iron, Mn, or both. If the substrate is continually wet, growers should reduce watering frequency or increase aggregate percentages in their substrate to facilitate drainage.
Learn more in the original e-GRO alert here.