Texas Root Rot

Texas root rot is a soil-borne disease caused by the fungus Phymatotrichum. The
disease occurs most commonly in June through September and affects more than two thousand
species of ornamental and native plants. It is one of the most common causes of death to
landscape plants in the Southwest. The fungus invades and kills plant roots, preventing the
absorption of water; if examined, the roots of infected plants are decayed and brown. During
the summer when temperatures are high, you will notice your plants’ foliage suddenly wilting.
The leaves will then die but remain on the plant. Unfortunately, when symptoms appear on the
plant leaves, the condition cannot be reversed by additional irrigation.

Root rot occurs in areas that have high temperatures and poorly draining, highly
alkaline soil. It affects fruit trees, ornamental trees, shrubs, vegetable gardens, and flowerbeds.
Fortunately, many of our native trees have some immunity to this disease. If Texas root rot is
prevalent in your area, replace non-native ornamentals with native plant material. When
planting in an area known to have been infected, follow these rules: Dig extra-deep holes at
planting time and amend the soil with at least 20 percent organic mulch as a backfill, sulfur,
iron chelate, and ammonium sulfate fertilizer to help acidify the soil.

Treatments are available for infected plants. Begin by digging under the tree’s canopy
and loosen all of the soil. Cover the ground with two inches of composted steer manure and
lightly scatter ammonium sulfate fertilizer on top of the manure. Then add soil sulphur at the
rate of one pound of fertilizer per one square foot. Mix all three materials into the top six to
eight inches of soil. Water the area after treatment to a depth of at least three feet. It is also
recommended to prune secondary tree branches to compensate for root loss. When treating for
root rot, also treat non-infected, susceptible plants because the root rot fungus can move
through the soil from diseased to healthy plants.

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