The newest leaves of manganese (Mn)-deficient palms emerge chlorotic with interveinal necrotic streaks (Figs. 1-3). As the deficiency progresses, newly emerging leaflets appear necrotic and withered on all but basal portions of the leaflets. This withering results in a curling of the leaflets about the rachis giving the leaf a frizzled appearance ("frizzletop") (Figs. 4 and 5). Within a single leaf, Mn deficiency symptoms are concentrated at the base of the leaf and are less severe or nonexistent towards the tip (Fig. 6). On new leaves of Mn-deficient Cocos nucifera, necrotic leaflet tips fall off and the leaf has a singed appearance (Fig. 7). In severely Mn-deficient palms, growth stops and newly emerging leaves consist solely of necrotic petiole stubs (Fig. 8). Meristem death often follows.
Late stage potassium deficiency symptoms are virtually indistinguishable from those of Mn deficiency at a distance and close examination is required to look for the interveinal streaking and basal (vs distal) symptom distribution that are characteristic of Mn deficiency.
Iron deficiency appears similar from a distance and close examination of new leaves for the presence of interveinal necrotic streaking is required to distinguish between the two disorders.
In Cocos nucifera, Mn deficiency causes the production of small new leaves that appear to have the distal portions of the leaflets burned off. In this species, it is very similar to the truncated leaf tip symptoms caused by boron deficiency.
Manganese deficiency is caused by insufficient Mn in the soil or by high soil pH, which greatly reduces Mn availability. In soils where Mn is marginally sufficient, cold soil temperatures may cause temporary Mn deficiency by reducing root activity levels. This is particularly common on Cocos nucifera in Florida. Composted sewage sludge and manure products have also been shown to strongly bind Mn when used as fertilizers or as soil amendments for palms.
Manganese deficiency is very common on alkaline soils, but can occur in containers if drainage is poor or soil temperatures are cool. Most species of palms can be affected, but Syagrus romanzoffiana, Acoelorrhaphe wrightii, Phoenix roebelenii, and Elaeis guineensis are particularly susceptible.