Zebra Chip

Zebra chip may sound like a fun new black-and-white striped snack, but it’s not. It is a bacterial disease that attacks potatoes.

Potatoes infected with zebra chip disease (USDA) CC BY 2.0

Like most bacteria, Candidatus Liberibacter solanacearum doesn’t move around very well alone. Instead, it lives in the gut of potato psyllids. Potato psyllids are tiny, sap-sucking pests. As they feed, the bacteria move from the insect to the plant, infecting the vascular tissue and tubers.

Potato psyllids carry zebra chip bacteria (Whitney Cranshaw, CSU, Bugwood.org) CC BY 3.0 US

Symptoms of zebra chip

There are no aboveground symptoms of zebra chip, but potato psyllid feeding causes foliage to turn yellow or purple. It can also cause pink or red discoloration of leaves. Zebra chip symptoms are only visible after you cut into a potato.

The zebra chip bacteria cause potatoes to store sugar instead of starch. That might sound like an idea for a new dessert food, but the presence of sugars causes vascular tissue to turn into ugly brown lines. When cooked, these brown lines turn black, hence the name. This condition also reduces crop size by 20 to 50%. Healthy-appearing potatoes from plants affected by zebra chip are more likely to sprout while in storage. Seed pieces taken from infected plants may not sprout at all, or they produce weak, infected plants.

Controlling zebra chip

The only way to control zebra chip is by managing potato psyllids. Yellow sticky sheets trap potato psyllids with little effort on your part. Spinosad can also be used to reduce potato psyllid populations. These treatments won’t eliminate the psyllids, but they will help. Inspect potato, bean, and pepper plants regularly for signs of psyllids.