Caring for Your Cycads
Popularity of Cycads for landscaping
Cycads are very popular as ornamental plants for landscaping. They are however difficult to care for especially in climatic conditions where insect pests such as the Cycad Blue butterfly and scaled insects thrive.
Young shoots attacked by the caterpillars of Cycad Blue butterflies
The caterpillars of the Cycad Blue butterfly are particularly distructive to the young shoots of the plant. In a heavy infestation the young fronds can be completely stripped of all their leaves. The lavae will take two to three days to hatch from the eggs and will immediately start eating the young shoots. Any small damage to the leaves of the young shoots at this stage will be magnified later as the leaves mature giving a ragged appearance to the outline of the fronds. If this is to be avoided, it is therefore very important to kill the lavae in the eggs before they even hatch. It is for this reason that systemic insecticides are not a good choice. Insecticides containing synthetic pyrethroid are very effective in killing the lavae and the caterpillar. They are also toxic to the adult butterfly. Two or three drops of dish-washing liquid can be added to the solution to aid the spreading of the liquid on the leaves. Spraying should commence even before the shoots emerge and should be repeated at regular intervals of no more than two days. It is easy to tell when the shoots are about to emerge as the Cycad Blue butterflies are attracted by the scent and they start laying their eggs on the crown of the plant. Spraying should be continued until the leaves have hardened and turned a dark green as the butterflies are so persistent they will continue to lay their eggs on the underside of fully-formed but not yet matured leaves. When these eggs hatch the lavae will start eating the tips of the leaves thus damageing them.
The shoots of young plants are particularly difficult to treat as the shoots themselves are sensitive to the insecticide. They shrivel and die if the concentration of insecticide is a little too high. The solution should be diluted well below the recommended doses. Fortunately even the diluted dose is potent enough to kill off the unhatched lavae. The photograph below shows a Cycad Blue butterfly laying eggs on a young shoot.
Infestation by scaled insects
Scaled insects attack the plant by attaching themselves to the underside of the leaves and sucking the fluid from them. They take some time to invade the leaves and establish themselves, hence they are found only on the mature leaves. They do not respond to normal insecticides because the coating of wax on their bodies prevents contact with the insecticides. One way to kill them is to suffocate them with a layer of horticultural oil which is normally applied by spraying. These insects are difficult to control since the infestation is on the underside of the leaves. I have found the ready-made solutions that come in the spray containers available off the shelf to be rather ineffective. I prefer to buy the concentrated white oil and mix it with water myself.
The photograph below shows a young plant with the base of its fronds badly infested with scaled insects. The white specks are the young insects which are mobile and move up the fronds to infest the leaves higher up. The darker areas are the adult insects which have permanently attached themselves to their chosen spots.
Parasitic ferns growing on the trunk
Ferns are often seen growing on the trunks of cycad plants. These ferns appear quite innocuous at first sight. It is only after you try to pull one off that you realise it is attached to an extensive and thick root system that is deeply embedded into the bark of the trunk. The roots often completely encircle the trunk and the only way to remove them is to dig them out with a knife. If these roots are not removed they will continue to draw nutrients from the host plants and, after some time new fern leaves will sprout from them. Apart from the ill effects of their parasitic nature the roots cause the bark of the trunk to take on a very untidy appearance. A fern leaf removed from a cycad trunk together with part of its root system can be seen in the image below.
