Frizzletop in Cycas revoluta   Cause and Cure

Background: Frizzletop is a dieback disease that affects the pinnae on Cycas revoluta plants. Cause: Frizzletop occurs in C. revoluta plants primarily because of the absence of (or an insufficient amount of) manganese in the soil. Frizzletop is caused by an excess of lime, resulting in alkaline soil surrounding the affected plant; as a consequence of which manganese is not available to the plant. (Note: Manganese is important to healthy plant growth as it is needed to provide proteins). Frizzletop often occurs in advanced C. revoluta s planted in new housing estates, where concrete usage is common; and building rubble is used for fill thus resulting in an excess of lime in the soil in garden beds. Cure: To restore the plant to normal, it is necessary to increase the acidity of the soil by making manganese available to the affected plant, through the application of Manganese Sulphate. The application of Manganese Sulphate has a twofold effect: 1) by supplying manganese for the plant, and 2) by providing sulphur to make the soil more acidic. Suggested Treatment: Application, by watering-can, of Manganese Sulphate, combined with an accompanying application of a liquid fertiliser (e.g. Nitrosol). Liquid fertiliser is used as a means of assisting the plant to absorb the Manganese Sulphate. The Manganese Sulphate/liquid fertiliser solution should be watered on to the fronds, the trunk (if applicable) and, also, on the soil immediately adjacent to the plant. The application of Manganese Sulphate generally should not exceed the manufacturers recommendations. One manufacturers suggested treatment is to dissolve 10 grams of Manganese Sulphate in 10 litres of water; however, in serious cases of frizzletop with mature/trunked plants, it may be advisable to apply up to 20-30 litres of the manufacturers suggested mixture, plus a proportionate amount of liquid fertiliser. Treatment is recommended as soon as the problem of frizzletop is noticed. The treatment should be carried out on a seasonal basis after the onset of frizzletop is identified, but not during winter. Treatment is suggested in early autumn, early spring and early summer - and such treatment, over a 12 month period, should correct the manganese deficiency. Once a healthy set of fronds is produced, the cure should be permanent - but to ensure its continued health, the plant should be fertilised periodically with a slow release fertilizer, so as to ensure that a sufficient level of available manganese is maintained. It is extremely important that the unsightly fronds are left on the plant during treatment, so that they assist in the absorption of the applied solution of Manganese Sulphate/liquid fertiliser by the affected plant. Figure 1. Cycas revoluta with frizzletop. Contributed by: Craig Thompson and Paul Kennedy (Figure 1 by Craig Thompson)