What’s Wrong With My Potato Plant?: 9 Problems and Solutions
Potatoes are one of the easiest root vegetables to grow in the home garden. They sprout from enlarged roots, called tubers, that work like seeds. Because of their unique sprouting process, potatoes may run into snags like diseases, pests, and poor growing conditions. Watch for problems, and try these recommended solutions from seasoned grower Jerad Bryant.
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Though potatoes are typically disease and pest-free, they may encounter problems when they’re growing in adverse conditions. Soggy soil, dry weather, and excessive heat can turn a healthy crop into a struggling, pest-riddled one.
Don’t worry, as most of these issues are easily solved with different growing methods and techniques. Simply give your potatoes what they need, and they’ll reward you with dozens of tubers at the end of the growing season.
Occasionally, these problems can ruin the year’s crop and prevent a successful harvest. The best thing to do is to take notes and learn from what went wrong to avoid it in the future. Crop rotation, mulching with compost, and paying close attention to the growing potato plants can help you thwart most problems before they grow out of control.
Espoma Garden-tone Organic Plant Food (4 lbs.)
Espoma Garden-tone Organic Plant Food (4 lbs.)
9 Potato Problems and Solutions
Without further ado, here are nine common potato problems with solutions accompanying them. Protect your tubers so you can eat them when they’re ready!
Mushy or Crumbly Tubers
Mushy, squishy tubers aren’t good signs. They’re a symptom of many potential problems, such as infections, chilly frosts, and soggy soil. Many infectious fungi and bacteria cause mushiness, and so too do improper growing conditions.
Bacteria, like Erwinia species, are typically the underlying cause of wet, mushy infections. They’ll have black growth surrounding the mushy portions. Fungal infections are a bit different. The Fusarium fungal species cause dry, black lesions in tubers and white, tan, or yellow mycelial tendrils. Other rots, whether from fungi or bacteria, can also cause mushy, crumbly symptoms.
Prevent these symptoms by planting potato pieces in moist, free-draining soil without sogginess or standing water. Ensure there’s good air circulation in the garden, and consider planting in a new location for a few years to starve soil-borne diseases. Always use certified pest and pathogen-free seed tubers from reliable growers.
Spots and Marks on Tubers
Spots, knobs, and pockmarks aren’t major issues for a potato crop. They’ll turn a perfect tuber into a mottled one, though they won’t affect the edibility of your harvest. A few different diseases and cultural conditions cause the formation of these various marks.
Fungi are the root cause of most skin disorders. They cause black scurf, silver scurf, and blight lesions. Watch for black or silver spots, raised bumps, and hard, black lesions. Conditions like black scurf are severe in cold weather, so always plant your seed pieces after late spring frosts.
Though fungi can cause these blemishes, irregular cultivation habits can also create marks and lesions, like lenticels. They’re small, whitish, and raised spots that form on the skin in soggy soils.
Prevent unnecessary blemishes by maintaining a moist soil culture throughout the growing period. Periods of shifting dryness and wetness may lead to knobby potatoes, and so too can these infectious fungi. Prevent the fungi by adding compost to the growing site and through crop rotation.
Knobby, Mottled Skin
Another condition, potato scab, causes mottled, rough potato skin. It’s caused by a bacterium, Streptomyces scabies, that often infects potatoes sitting in alkaline soils. The condition is unsightly, but you can skin the tubers and eat them if you’d like. Scab doesn’t affect the quality of the flesh inside.
Scab often infects new potato tubers by spreading from seed potatoes onto the new ones that form underground. It’s easily preventable by sourcing disease and pest-free potato pieces from a reputable source, either online or at a local nursery.
Crop rotation, again, is highly successful in limiting this disease’s spread. Plant potato seeds or pieces in the same spot every three to four years, and use fresh potting soil or compost if you’re planting in containers.
Holes in Potatoes
Pesky pests can tunnel into your tender potato tubers! Insects like wireworms, flea beetle larvae, and white grubs may eat into the swelling potatoes. Some unique, inventive traps and prevention methods can help control these insects without harming the local ecosystem.
One clever wireworm trap takes advantage of old yogurt containers. Poke holes at the top of the containers near the lid; make them wide enough for your finger to fit through. Put fruit scraps in the bottom of the container, snap the lid on, then bury the containers an inch below the ground near your potato crop. Mark the containers with flags so you don’t forget where they are.
The wireworms will enter through the holes on the sides, fall onto the fruit scraps, and get stuck on the bottom. You may trap a few worms—remove them and put them back in the garden to make use of their beneficial properties. Take the wireworms out, kill them, and throw them back in the yard to decompose.
Chickens, garden snakes, and birds eat white grubs. Encourage them to your yard with a water source so they can drink while they dine. Flea beetles are more challenging to control. Remove weeds, debris, and other protective spots where they hide. Protect young potato plants with a floating row cover in spring.
Green Skin
Green skin is incredibly common! It’s a natural response of the potato plant to sunlight. If sunlight reaches a tuber or two, it’ll turn their brown skin green as they begin to develop chlorophyll and photosynthesize. In the process, a toxic group of substances called glycoalkaloids also develops. Solanine is one of them.
This is why it’s important not to eat green potatoes. They can cause stomach upset, indigestion, and, in severe cases, brain damage. Use the green ones as seed pieces for planting, or throw them in your compost pile.
Green skin can develop on your crop in the field or while it’s in storage. Protect budding plants with compost or a similar mulch, and store harvested portions in a dark closet or pantry.
Cracking Skin
Cracking skin may seem like a disease symptom, but it results from irregular watering. Like tomatoes that crack in late summer, swelling tubers are subject to cracking when moisture levels fluctuate. A long wet period followed by a long dry one often causes the symptoms.
If no rots or lesions are present, you may eat the harvest as you normally would. Simply peel the hard portions before cooking. If, however, there are signs of rot, it’s best to throw the cracked tubers away.
Prevent cracking skin by maintaining consistent moisture in the soil. Water as often as necessary so it feels like a wrung-out sponge when you squeeze it.
Leaf Spot
Leaf spots early in the growing season often appear because of early blight, a condition that stems from a fungal infection. The fungus attacks nutrient-starved plants in spring, causing small circles that are black or brown.
The circles develop into large lesions with yellow rings. They’ll grow progressively larger until entire leaves wither and fall, which spreads the disease further. These spots differ from late blight spots in that they stay between leaf veins.
Once leaf spot occurs, there’s little that can remove it. Some sprays may prevent its spread, though they won’t kill it completely. Prevent it by planting resistant varieties, practicing crop rotation, and keeping your plants happy and healthy. Stressed plants are more likely to develop leaf spot than healthy ones.
Water-Soaked Lesions
Water-soaked lesions that form late in the season are signs of late blight, another fungal condition. It causes dead spots that grow without regard to leaf veins, creating irregular brown patches on the foliage. Lower leaves may have a whitish, powdery growth on the outer portions of the lesions.
Late blight is most severe in damp, cool, and humid conditions that are common in late summer and autumn. After infecting the leaves, it’ll begin to creep into the tubers and cause brown, pebbly flesh underneath their skin.
Management is key in preventing the spread of late blight particles. Destroy infected tubers, stems, and leaves far from the growing site. Rotate the crops annually into a new region, and grow blight-resistant varieties.
Wilting Shoots
Black scurf, the fungal pathogen that causes black marks on tuber skin, also leads to wilting shoots in early spring. If the weather is too cold and mild, the shoots will grow slowly and face increased pressures from the other form of black scurf, called Rhizoctonia stem canker.
Both black scurf and stem cankers are caused by the fungus Rhizoctonia solani. Watch for wilting potato stems that wither shortly after they emerge from the ground. If stems wilt in the summer, it may be from early or late blight rather than stem cankers.
Never plant potato pieces if they have the characteristic black, raised spots on their skin. Use certified pest-free pieces, and discard infected ones far from the garden. A late planting can be beneficial, as it causes rapid growth that may outcompete the fungus.
Key Takeaways
- Potatoes are easy to grow, but that doesn’t mean they’re problem-free or pest-free!
- Reduce the likelihood of pests or pathogens by growing potatoes under the proper conditions.
- Though chemical sprays can prevent or reduce the spread of diseases, they rarely eradicate them from entire stands of potatoes.
- Rotating crops, using compost, and planting at the right time are all essential methods for preventing problems.
- If problems persist, consider trying disease-resistant potato varieties.
