How to Manage Pests

Pests in Gardens and Landscapes

Damping off and root dieback of carrots—Pythium spp.

Carrots infected with the Pythium fungus fail to emerge, or they fall over and die soon after emerging. Stems usually have a dark, shriveled portion at the soil line. Pythium spp. may also cause root dieback of carrots by producing excessively branched or stubbed roots. The fungus kills young tap roots less than 2 weeks after seed germination, reducing root length and/or stimulating multiple root formation.


Pythium is spread in water and soil. Very wet soil conditions favor the disease. Plant in light soils such as sandy loam. Maintain uniform soil moisture at seed depth until seedlings emerge. Avoid planting during high temperatures and keep soil as cool as possible when the weather is warm. Be sure seeds are not planted too deep. Protect soil surface from rain or sprinklers. Avoid overwatering and provide good drainage.

For more information, see the Damping-off Diseases in the Garden Pest Note.

Damping off
Roots of young carrot plants damaged by Pythium compared with healthy plant

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