Pink root

About

Pink root turns onion roots pink to purple and kills them, so bulbs stay small. The fungus is a common soil inhabitant and gets worse when onions are grown in the same place year after year.

Also called pink root

How to recognize it

Symptoms

Roots turn light pink, then red to purple, then shrivel and die, and the color can move into the bulb's outer scales. Plants are stunted with small bulbs but rarely die.

Worse when

Warm soil (75 to 85°F), repeated onion crops in the same spot, and weak plants.

How it spreads

The fungus lives in soil more or less indefinitely and builds up with each onion crop; it needs no wound to infect.

When

Summer, when soils are warm.

What to do, gentlest first

Prevention works best; most sprays only protect healthy leaves and can't cure infected ones. Always read and follow the product label.

1. Rotate away from onions Prevent

   Grow non-onion-family crops in the bed for three to six years.

2. Resistant varieties Prevent

   Some onion varieties resist pink root, though results vary by location and strain.

3. Healthy soil and plants Prevent

   Keep soil in good tilth and fertility and control other pests so plants stay vigorous.

4. Soil solarization Prevent

   In hot-summer areas, solarizing the bed during a summer fallow before fall planting has worked well (UC IPM).

Plants it affects

Chives, Garlic, Onion