How to Manage Pests

Pests in Gardens and Landscapes

Phytophthora root rot on cole crops—Phytophthora megasperma

The external surfaces and internal tissues of roots infected with Phytophthora are dark in color and are rotted. Leaves, especially older ones, turn purple red and wilt. With time the entire plant wilts. The stem near the soil line may turn black and become soft.


Phytophthora root rot usually occurs only if cole crops are planted in poorly drained, fine-textured soils that are kept overly wet. Prepare soil so that low spots are minimized. High, well-draining beds will discourage disease development. Irrigation should be carefully monitored to avoid excessively wet soil conditions. Be careful not to stress plants with underwatering; ensure an even supply of moisture to help suppress disease development.

For more information, see the Phytophthora Root and Crown Rot Pest Note.

Brussels sprouts infected with Phytophthora
Brussels sprouts infected with Phytophthora

Statewide IPM Program, Agriculture and Natural Resources, University of California
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