Small Brown Spots on the Stem of My Schefflera

Alternaria Leaf Spot

• Alternaria leaf spot is a fungal disease that infects the schefflera plant’s foliage and stems. A spore-borne disease, the fungus germinates on dead debris and defoliation that lies around the schefflera’s planting area. The spores are transported onto the plant’s foliage and stems by water and wind, and the disease is most aggressive when temperatures average between 64 and 86 degrees Fahreneheit.

Effects

• Once the schefflera is infected with alternaria, the plant develops small, dark-colored spots on its foliage. Aggressive infections also create spots on the schefflera’s stems and stalks of the schefflera. The pin-sized spots coalesce into larger, decaying spots that are often surrounded by yellow halos. The enlarged spots girdle the stems, causing dieback and death of the tissue, while the entire schefflera experiences dieback and premature defoliation.

Prevention

• Alternaria fungal spores require water to germinate, and these fungal spores are only able to infect the schefflera when its foliage and stems are wet. The potential for alternaria leaf spot infections is greatly reduced when the schefflera’s foliage is kept dry. The schefflera plant should be watered deeply at soil level to ensure that all of its roots receive water. The soil should be allowed to dry slightly between each watering to encourage strong roots and to reduce the potential for spore development. Planting the outdoor schefflera in full sunlight and keeping the schefflera’s planting location free of debris and defoliation also helps to reduce the potential for infections.

Treatment

• Alternaria leaf spot infections can be controlled with timely pruning and fungicidal spray treatments. The infected foliage and stems should be pruned from the schefflera plant with sharp, sterile shears. It is important to sterilize the shears between each cut to prevent spreading the infection to the healthy areas of the tree. Fungicidal sprays should be applied thoroughly to the plant to ensure that every area of the plant receives the chemical. Apply the fungicidal spray according to the directions to avoid injury the plant, and reapply as necessary. Chemical treatments are only effective when applied during the early stages of infection.