What Are the Causes of Mold in Palm Trees?
- The coconut mealybug (Nipaecoccus nipae) inhabits most species of palm trees. The feeding on the foliage by adult females and immature larvae results in the development of a black, sooty mold. As the mealybugs feast on the leaves, their excrement -- honeydew -- sticks to the foliage and the sooty mold forms on the tree. The damage is largely aesthetic, but it can hinder the ability of the tree to conduct photosynthesis, resulting in a loss of vigor in the palm.
- The loss of energy in the palm contributes to the yellowing of the leaves and their potential defoliation. The mealybugs produce a waxy coating that protects them from insecticide, making their chemical management difficult. If the infestation is light, simply washing the infected areas with a garden hose and water or pruning away infected limbs and fronds can be helpful as can the application of insecticidal soaps or horticultural oils. However, these methods demand repeated effort.
- A number of fungi of the Phytophthora species cause root and crown rots in palm trees, resulting in the formation of cankers and an oozing mold from the bark of the tree. This oozing material is typically red or brown and also displays beneath the surface of the bark, showing intense discoloration of the wood. Stains, streaks and open wounds form on the trunk of the palm. When these symptoms come to pass, the tree is rotting from the inside out with the mold displaying prominently on the tree.
- What appears to be mold growing on a Sago palm tree is actually an insect known as the cycad or aulacaspis scale (Aulacaspis yasumatsui). The presence of this pest on the tree covers it with what looks like a white mold but is actually a large mass of thousands of the insects clumped together. It must be noted that this scale infests only Sago palms and does not inhabit true palm trees; the Sago palm is not actually a member of the palm family, but instead belongs to the species of plants known as cycads.