Question: For 2 years, now, some of our Pontiac potatoes look like the one in my photo. What is it and how do we fix it?
Answer: It’s hard to tell with the photo, but this could be Zebra chip disease, a bacterial disease that was first reported in Utah about 7 years ago. The potatoes are perfectly safe to eat.
Zebra chip is transmitted by potato psyllids, very small insects, when they feed on the foliage of potato plants and other susceptible plants. Psyllid feeding may cause the foliage to look like there is a nutrient problem — yellowing or reddish — pink areas.
The outside of affected potatoes will look perfectly normal even though the bacteria will move through the vascular tissue of infected plants, including the tissue in the potato tubers, where it can cause some discoloration that is only seen when the potatoes are cut.
The discoloration inside the tubers may not be very noticeable unless the potatoes are fried. When potatoes with Zebra chip are fried the affected tissues are much darker. Most home gardeners consider this a cosmetic issue, but for commercial growers who grow their potatoes for processing as French fries or potato chips, Zebra chip can mean their potatoes will be rejected.
Zebra chip is difficult to control because potato psyllids may be in the garden before you notice them, but here are some things you can try.
Don’t use any potatoes from this year’s crop as seed potatoes for next year.
Begin look for psyllids on the underside of leaves early in the garden season. Use an appropriate insecticide if you need to. Yellow sticky cards are another way to watch for psyllids.
There is no cure for Zebra chip disease, so remove infected plants as soon as you can.
Consider using low tunnels of floating row cover after planting to exclude psyllids.
Holiday gift giving
Is there a gardener on your Holiday shopping list? If you’re looking for gift ideas, here are some suggestions.
- Gardening gloves. You’ll find them made from a variety of materials.
- A new kneeling pad. From simple foam pads to garden kneelers that convert from benches with hand grips that make it easier to get down to the soil and back up again.
- Plant markers/tags. You’ll find tags and labels in many different materials and sizes for use indoors or outdoors.
- A gift card to a favorite nursery or online seed catalog. Seed companies have been promoting new 2021 varieties of flowers and vegetables for several weeks now and gardeners are starting to plan their gardens for next year.
- A new hat. Gardeners need sun protection, even when the weather isn’t hot.
- A circle or stirrup hoe. Tools like this make it easy to do weeding up close to plants without disturbing the soil too much.
- A Mason bee house. Solitary bees are important pollinators in the garden.
- An outdoor thermometer. There are lots of styles to choose from. Whether it’s a simple dial-faced thermometer that will attach to a post or a remote sensing model that reports to a base station indoors, it’s nice to know what the temperature is in the garden.
- A soil thermometer. It’s an inexpensive little tool for gardeners who want to check the temperature of their garden soil before they start planting seeds.
- An adjustable nozzle for the garden hose. Multiple spray patterns and an on-off trigger make a hose more useful.
- A set of nice trowels or hand weeders. Your gardening friend might have favorite thand tools already but if not, a high-quality trowel or weeder would be a nice addition to their garden tools.
- A garden sculpture or fountain. There’s something available for every style.
- A new container or cache pot for container gardening.
- A gardening book or eBook. There are new books every year and lots of old classics, too.
- Membership to a botanical garden.
Tuition for the Master Gardener course- registration is open now. Classes will meet for two and a half hours every Thursday at 1:00 p.m. or 6:00 p.m. beginning Jan. 21, 2021 and will end April 29, 2021. You’ll find course details and registration information online
- An LED grow light. For a gardener who likes to grow their own transplants, these lights make it easier to have healthy plants to take out to the garden.
- A heat mat for starting seeds or cuttings indoors.