What Causes Galls on House Plant Stems?

Eriophyid Mites

• Eriophyid mites are microscopic arachnids, which are closely related to spiders. They are almost impossible to see without magnification, but the galls they create are obvious. Eriophyid mites dig into plant tissue, rupture cell walls and feed on the contents of the cell. The plant responds by increasing cell production and growing extra tissue. These growths can occur anywhere on the plant, from the stem to flower buds. The appearance of a gall often depends on the species of Eriophyid mite infesting the plant, but in general they are knotty swellings. Galls normally change shape and color as they age.

No Harm, No Foul

• On larger plants galls are not typically damaging. They are unsightly, but don't do any harm. On houseplants, however, galls may be more troublesome. Galls are living tissue and as such require water and nutrients. Several galls on the stem of a houseplant may reduce its vigor. Galls on a houseplant are much more noticeable than those on a tree. If you can prune them out, do so. If you can't prune them out, you can live with them or replace the plant.

Nematodes

• Nematodes are microscopic worms that live in the soil. Much like Eriophyid mites, nematodes invade plant tissue and feed on the contents of cells. Nematode feeding causes galling on roots and the lower stem. Unlike Eriophyid mites, nematodes can severely affect, or even kill the plant. Galling on roots and stems reduces the amount of water and nutrients available to the plant. Over time, an infestation of nematodes can kill a houseplant.

Control

• Once your houseplant is infested with nematodes, you can't save it. You may take steps, however, to ensure that you bring no other infested houseplants home. The nematodes in your houseplant likely came from the soil in your garden. Using soil from a garden bed or even using the same trowel with pots and garden can spread nematodes. They can travel on hands, clothing, pets or anything else to which dirt clings. Practice rigorous sanitation to avoid spreading nematodes. Use only fresh garden soil and keep your plants healthy with proper amounts of water and fertilizer.