If you notice a white, mould-like growth on your palm tree, you are likely the owner of a sago palm tree. Though not a true palm, sago palms belong to the group of trees called cycads which, as this tree's name suggests, look quite a bit like true palms. In addition, the growth that looks like mould is actually a pest infestation rather than fungi. Though identifying this issue seems a bit confusing, control is straightforward and effective.
Provide optimal care to your sago palm tree to prevent pest infestations. Vigorous trees have a greater ability to avoid pest problems and overcome those that occur. Sago palms are versatile plants that thrive in both sunny and shaded areas of the home landscape. Maintain moist, well-drained, slightly acidic soil high in organic content, suggests the Clemson University Extension. As cycads are particularly sensitive to nutrient deficiencies, bring a sample of your soil to your local county extension agent before fertilising. Make any recommended amendments to improve the essential balance of nutrients like nitrogen and magnesium that, when out of balance, can lead to disease.
Though the white growth on your tree looks like mould, it is a collection of scale pests. Known as cycad or aulacaspis scale (Aulacaspis yasumatsui), this problem attacks sago palms that are typically prized for their pest and disease resistance. These scales, a type of armoured scale, display pear-shaped bodies covered in hard plates. Exhibiting a white to pale yellow hue, scales reach a length of up to .06 inches. Due to their whitish colour and the waxy substance that coats their bodies, these tiny insects form groups that make them easy to spot and often cover the entire plant.
Examine the undersides of your tree's fronds even if you do not notice a problem as cycad scales often congregate beneath fronds first. Scales are sucking pests that insert their mouths into plant tissue to suck sap. Look for tiny yellow specks that occur as a result of feeding as well as a thick white coating on foliage and diminished health. When left untreated, cycad scales travel toward the ground, infesting your tree's trunk plant parts beneath the soil. Severe infestations lead to tree death in less than a year.
Treat this problem as soon as you notice symptoms as it becomes more challenging to control when scales spread into soil. Manage these pests by pruning away and destroying affected plant parts to decrease the severity of the infestation and to prevent it from spreading to other plants. Sanitise pruning shears between each cut and before moving to another plant. Release natural enemies like parasitic wasps (Coccobius fulvus) onto your sago palm as these bugs kill scales but do not harm desired plants. Purchase these bugs from garden supply stores.
For severe problems, apply a low-toxicity insecticide horticultural oil until it saturates infested areas of the tree for effective control. Apply horticultural oil once a week for five weeks, suggests the University of Florida Institute of Food and Agricultural Sciences Extension.