Translucent, yellow spots One of the most diagnostic early symptoms on many species is this translucent yellow-orange spotting of the oldest leaves. This is best viewed by holding these leaves up to the light as shown here. Sometimes these translucent spots are accompanied by necrotic spots as well.

Leaflet tip necrosis Some species, such as royal palms and this Dypsis cabadae, do not produce spotting of any kind on their older K-deficient leaves. Marginal and tip necrosis of the leaflets is the only symptom observed. As the marginal necrosis spread towards the midvein in each leaflet, the vascular connection to the rachis is disrupted, thereby causing the distal portion of each leaflet to become desiccated. Note that the base of the leaflets towards the base of the leaf remain alive and green. In some species, the neccrotic distal portion of K-deficient leaflets becomes curled or frizzled as shown here. Since this disorder occurs on the oldest leaves first, it is not to be confused with “frizzletop” or manganese deficiency. That disorder occcurs on the youngest leaves only.

Leaflet tip necrosis On most fan palms, older leaves will show a orange discoloration, with the tips of leaflets often necrotic. Spotting on the leaflets may or may not be present, depending on the species. In some species, leaflet tip necrosis is the only symptom observed.

Leaflet tip necrosis On date palms (Phoenix spp.), necrosis occurs only on the tips of leaflets, not the margins as in most species. This necrosis and discoloration will be most severe towards the tip of the leaves, with the leaf base often being symptom-free. In P. canariensis, there is typically no leaf discoloration with K deficiency, but the necrotic leaflet tips often break off leaving the green older leaves with ragged and necrotic margins. In P. dactylifera, older K-deficient leaves will have typical yellow spotting, as well as necrotic leaflet tips.

Necrotic leaf spots On some species such as Arenga spp. And Caryota spp. (shown here), the only symptoms are necrotic spotting of leaflets on the oldest leaves. They appear similar to leaf spots caused by various fungi, however, true leaf spots occur on most leaves within the canopy and are not restricted to the tips of the oldest leaves.

K versus Mn One way to differentiate between K deficiency and Mn deficiency is to note the distribution of symptoms on a single leaf. On a K-deficient leaf, the symptoms are most severe towards the tip and least so towards the base. In the case of this older leaf of a K-deficient coconut palm, the basal leaflets show no deficiency symptoms whatsoever, the middle aged leaflets show yellow and necrotic spotting and marginal necrosis, and finally the most distal leaflets are almost completely necrotic.

K is mobile Potassium, like N, is a mobile element within the palm. Thus symptoms occur first on the oldest leaves as these are depleted of their K in order to sustain growth of the new leaves. The oldest leaf (on left) in this K-deficient spindle palm shows necrosis and frizzling of most leaflets, but the rachis and the proximal portion of most leaflets remain alive, The next oldest leaf (on right) shows no necrosis, but has extensive orange translucent spotting on its leaflets. The youngest leaf is completely symptom free.

Once K has been depleted from older leaves, newer leaves will begin to show deficiency. Trunk will begin to taper just below the crown. Once a K-deficient palm exhausts all of the K from its older leaves, new leaves will emerge chlorotic, reduces in size, and frizzled. The trunk diameter just below the crown will often show a tapering due to the reduced vigor of the palm. Potassium deficiency is the number one cause of mortality in royal palms and the palm in the center was dead six weeks after this photo was taken. Although it is not clear on this dark photo, the gray-brown frizzling on the older leaves of royal palms is invariably caused by K deficiency. These half dead necrotic older leaves that persist on the palm are not dead from old age. A healthy, naturally senescing old leaf will be completely green one day, completely yellow the next day, and completely brown and fall off the third day. A half dead old leaf retained by a palm for weeks or months at a time is not naturally senescing, but rather is suffering from K deficiency. Yikes!

Late stage K deficiency in coconut palm. This coconut palm is suffering from late-stage K deficiency. It died soon after this photo was taken. Note the tapering trunk just below the crown. The entire crown is chlorotic, and frizzled, with the symptoms most severe towards the leaf tips, not the leaf base as would be the case with Mn deficiency.

Magnesium (Mg) Deficiency Marginal chlorosis of leaflets or leaves Central part of leaves or leaflets remain distinctly green Most severe on oldest leaves

Most common deficiency on P. canariensis Magnesium deficiency is the most common naturally occurring deficiency on Phoenix canariensis. If it is observed on any other species of palm in the landscape it has probably been induced by improper fertilization. Symptoms include the broad lemon yellow bands along the margins of the oldest leaves. The central portion of the leaves remains distinctly green. The leaflet tip necrosis seen here on the oldest leaves is K deficiency superimposed on Mg deficiency. Mg deficiency does not by itself cause leaflet necrosis.

Magnesium Deficiency Potassium Deficiency This is Mg deficiency on Phoenix roebelenii. Note the center of the leaf remains distinctly green right down to the tip of the leaf. Potassium Deficiency

K and Mg deficiency. Mg occurs mid-canopy as well as oldest leaves. In fan palms, there is typically a broad lemon yellow band around the perimeter of the oldest leaves. The necrotic leaf tips on the very oldest of these leaves is probably K deficiency superimposed on Mg deficiency. Mg deficiency often occurs mid-canopy, as well as on the oldest leaves. K and Mg deficiency. Mg occurs mid-canopy as well as oldest leaves.

Mg deficiency can also occur on the individual leaflets. Sometimes Mg deficiency will be expressed not as lemon yellow bands surrounding the entire leaf, but rather as lemon yellow bands along the margins of individual leaflets. Both types of symptoms can occur on the same species, or even on the same plant. Mg deficiency can also occur on the individual leaflets.

Manganese (Mn) Deficiency Interveinal chlorosis with necrotic streaking Withering or frizzing of leaflet tips More severe at leaf base than tip Death of meristem Affects youngest leaves only

Frizzletop Manganese deficiency, or “frizzletop” is a common problem on queen palms. New leaves will emerge chlorotic with longitudinal necrotic streaking within the leaflets. Once this necrotic area expands sufficiently to affect the midvein of the leaflet, the portion of the leaflet distal to this necrosis will wither and curl, giving the leaves this frizzled appearance. Note that the older leaves on the palm are normal in length. Manganese deficiency affects only the youngest leaves. If leaves of all ages are reduced in size, chlorotic, and frizzled, this is probably late-stage K deficiency. Of course, it is not unusual to find both K and Mn deficiencies on the same palm, making diagnosis more difficult.

Frizzletop In severe cases, new leaves will emerge as necrotic petiole stubs, the leaflets being severely reduced in size and necrotic as seen here. Death of the meristem can quickly follow.

Mn deficiency on Phoenix roebelinii Note frizzling at the base of the leaf and not at the tip as in K deficiency. Manganese deficiency on Phoenix roebelenii. Note frizzling of leaflets at base of each leaf, rather than towards the tip.

Longitudinal necrotic streaks Manganese deficiency typically causes longitudinal necrotic streaks within leaflets, in this case, along the mid vein of each leaflet.

Scorched appearance on coconut palm Manganese deficiency in coconut palm has a scorched appearance, looking as though the leaflets had been singed off with a torch. This could be confused with Boron deficiency, however in that case the sides of the leaves are not singed as with Mn deficiency.