Potato cyst nematode

Globodera spp.

also called PCN, potato eelworm, potato root eelworm

Potato plants that yellow and die off early from the bottom up, with tiny pinhead cysts dotting the roots; the cysts survive in soil for many years.

Nematode Serious Soil-borneSpread on tools & handsSpread in water Spreads to neighbors

What you'll see

Tiny white, yellow, then brown cysts the size of a pinhead cling to the roots.
Foliage yellows and dies back early, working up from the lower leaves.
Plants wilt in warm weather and crop poorly, with small tubers.
Patches of poor growth appear and spread across the potato bed.
Roots are sparse and the plant looks starved.

Why it happens

Potato cyst nematode is a microscopic roundworm of the genus Globodera. The female swells into a cyst on the root, and when she dies her body becomes a tough case holding hundreds of eggs. Those cysts are moved around on soil clinging to tubers, tools, boots, and machinery.

It builds up wherever potatoes or tomatoes are grown too often on the same ground, and the cysts can lie dormant in the soil for twenty years, hatching when a host is planted.

Treating it

There is no cure once present; lift and destroy the crop rather than saving tubers from it.
Stop growing potatoes and tomatoes on the ground for many years to starve it out.
Never save seed potatoes from an infested plot.
Keep plants fed and watered to squeeze a little more from a light infestation.

Keeping it away

Rotate potatoes on a long cycle and never plant them in the same spot year after year.
Buy certified seed potatoes rather than saving your own.
Grow resistant maincrop varieties where numbers are known to be high.
Clean soil off boots, tools, and barrows to avoid spreading cysts between beds.

Who gets it

Potatoes and tomatoes, the two crops in which it completes its life cycle.