Although potatoes are easy to grow, there are a number of diseases, pests and growth issues that may arise. To successfully manage these problems, you should be able to identify them. You probably won’t be able to reverse all conditions and may need to destroy some plants. However, catching the problem early can make all the difference. So, pay close attention to the health of your potato plants and inspect them thoroughly at the first signs of sickness. Here are a few common problems you’ll face when growing potatoes.
1. Plants do not germinate after planting seed pieces
If you’re planting store-bought potatoes, you need to know that most are treated to prevent sprouting. Therefore, only plant certified seed potatoes. Furthermore, ensure your seed potatoes have at least, two eyes on each piece before planting.
2. Plants don’t grow past soil level
Cutworms are usually found curled under the soil. They tend to chew on stems, roots, and leaves. Keep your field free of weeds and sprinkle wood ash around the base of plants.
3. Sprouts fail to grow or die young
Leaf margins brown and curl upward; stem base becomes dark brown, black, and slimy; tubers become slimy brown-black at stem end. Blackleg or black scurf. Blackleg is a bacterial disease where sprouts rot at soil level. Black scurf is a fungal disease where stems have brown sunken spots below the soil level. Remove all infected plants and destroy infected tubers. Add organic matter to planting bed; make sure soil is well-drained. Plant certified disease-free potato tubers. Rotate crops. Cover seed potatoes shallowly for quick emergence.
4. Leaves are slightly curled with small shiny specks and yellowish
Potato aphids are small, oval, pinkish to greenish pear-shaped insects that colonize on the undersides of leaves. They leave behind sticky excrement called honeydew which can turn into a black sooty mold. Spray away aphids with a blast of water from hose pipe. Use insecticidal soap.
5. Small holes in leaves and small bumps or spots on tubers
Flea beetles eat small holes in the leaves of seedlings and small transplants. The larvae feed on tubers. Peel away tuber damage. Pick beetles off plant. Spread diatomaceous earth or wood ashes around seedlings. Cultivate often to disrupt life cycle and keep the field clean
6. Leaves are cut off
Blister beetles are long, slim reddish-bronze colored beetles with red-coppery legs that feed on leaves. They secrete oil that can cause the skin to blister. Wear gloves and handpick them from leaves and destroy.
7. White speckling or stippling on the surface of leaves
And, leaf margins turn brown; leaves appear scorched and wilted. plants are stunted and dwarfed; tuber is malformed and cracks. Potato yellow dwarf virus is transmitted by leafhoppers. Leaf hoppers are green, brown, or yellow bugs with wedge-shaped wings. They jump sideways and suck the juices from plants. Use insecticidal soap. Cover plants with floating row covers to avoid leafhoppers. Destroy diseased plants and control leafhoppers. Plant disease free seed potatoes.
8. Leaves turn pale green, yellow, or brown
They also have dusty silver webs on undersides of leaves and between vines. Spider mites suck plant juices causing stippling. Spray away with a blast of water or use insecticidal soap or rotenone. Ladybugs and lacewings eat mites.
9. Leaves are mottled and become crinkled.
Mosaic virus is transmitted by aphids. Control aphids with pyrethrum or rotenone. Plant disease free seed potatoes. Plant resistant varieties: Chippewa, Katahdin, Kennebec, Monona, and Snowflake. Remove diseased plants and weeds.
10. Gray blotches on older leaves; tunneling in leaves
Potato tuberworms are small caterpillars, the larvae of a moth that lays eggs on foliage. They tunnel through interior of leaves. Handpick and destroy. Hill up soil over tubers to keep worms from reaching tubers.
11. Plants are green topped, no tubers
Temperatures are too warm. Potatoes require cool nights below for good tuber formation. Plant so that tubers mature in cool weather.
12. Spindly cylindrical stems
Witches bloom is a virus disease transmitted by leafhoppers. Stems are elongated and plants set many small tubers. Plant is mostly leafy growth; leaves roll up and have yellow margins. Destroy diseased plants. Plant disease-free seed potatoes. Control leafhoppers.
13. Stems have irregular dead streaks
Manganese level in acid soils may be high. Test the soil. Apply lime if manganese level is high. Grow resistant varieties: Canso, Green Mountain, McIntyre.
14. Plants stunted; yellowish-black streaks inside stems
Fusarium wilt is a soil fungus that infects plant vascular tissue especially where the soil is warm. Fungal spores live in the soil. Remove and destroy infected plants. Rotate crops. Plant certified disease-free potatoes. Plant resistant varieties: Irish Cobbler, Kennebec.
15. Leaves turn yellow and then brown from the bottom up
The plants lose vigor; plants appear stunted; stems, roots, and tubers have tunnels. Wireworms are the soil-dwelling larvae of click beetles; they look like wiry-jointed worms. Check soil before planting; flood the soil if wireworms are present. Wireworms can live in the soil for up to 6 years. Remove infested plants and surrounding soil.
16. Leaves and stems have irregular grayish brown water-soaked spots or rings
Gray-white growth appears on the underside of leaves. Tubers have brown-purple surface scars; tubers rot in storage. Late blight is caused by fungus that infects potatoes, tomatoes, and other potato family members. It favors high humidity and temperatures. Keep the field free of all plant debris and avoid overhead irrigation. Remove volunteer potatoes before planting. Plant certified seed potatoes and resistant varieties such as Kennebec, Cherokee, and Plymouth. Keep tubers covered with soil. Cut vines 2.5cm below the soil surface and remove vines 10 to 14 days before harvest. Do not harvest under wet conditions.
17. Young leaves fail to enlarge
New leaflets roll upward and turn reddish purple color, or topmost leaves, become yellow. Potato purple-top wilt is synonymous with aster yellow; it is a viral disease spread by leafhoppers. Plant certified disease-free seed potatoes. Remove and destroy diseased plants. Keep the field clean of plant debris. Control leaf-hoppers.
18. Leaves curl upward
Older leaves turn yellow, then brown; young leaves show purple margins. Nodes and petioles are enlarged. Tubers may be visible. Plant may turn brown and dry. Potato psyllid is light gray-green to dark brown or black winged insects about the size of an aphid; they are flat and disk-like before plumping up at maturity. They inject a toxin into leaves as they feed causing the plant to yellow. Use yellow sticky traps to control psyllid.
19. Tiny bumps on tubers, brown spots on tuber flesh
Nematodes are microscopic worm-like animals that live in the film of water that coats soil particles; some are pests, some are not. Pest root nematodes feed in roots and can stunt plant growth. They are more common in sandy soils. Rotate crops. Solarize the soil with clear plastic in mid-summer.
20. Leaf tips and margins yellow, gradually brown and die
Tubers have irregular brown spots throughout flesh. Lack of moisture or inconsistent moisture during hot, dry weather. Place 5-8 cm of organic mulch across planting bed to conserve soil moisture. Deep water potatoes 2 to 3 hours at a time; do not water again until the soil has dried to a depth of 10 to 20 cm.
21. Older leaves yellow and die
Brown streaks on lower leaves stems split lengthwise; stem end of tubers discolored around eyes. Verticillium wilt is caused by a soil fungus. It favors cool soil and air temperatures. Avoid planting where tomatoes, potatoes, peppers, eggplant, and cucumber family plants have been recently growing. This disease is most evident in hot weather when the plant is loaded with fruit and water is short. Plant resistant varieties: Houma, Cariboo, Red Beauty. Bacterial wilt also can cause these symptoms; black-brown ooze seeps from cut stems.
22. Tubers have brown streaks and roots are growing from inside tubers
Nutsedge is a perennial weed that grows in many potato growing regions. The weed’s rhizomes will penetrate potato tubers. Keep potato plantings free of nutsedge. Nutsedge tends to grow in areas that are not well drained.
23. Leaves turn light green, wilt, then dry; tubers turn watery and brown
Plants and tubers exposed to hot sun and dying winds after cloudy weather. Screen plants during extremely hot weather. Do not leave tubers in hot sun.
24. Pink areas around eyes of tubers
Pinkeye occurs on tubers in wet soil. The cause of pinkeye is not known. Plant in well drained soil.
25. Marble-sized potatoes grow directly from potato eyes
Cell sap is concentrated in tubers. Store seed potatoes in a cool, dark place. Plant seed potatoes later in season.
26. Stems at soil level are covered with purplish, dirty grey fungus
foliage curls, turns pinkish to yellowish; dark brown or black masses on tubers. Black scurf or Rhizoctonia is a fungal disease that favors warm soil. Remove infected plants and plant debris that harbor fungal spores. Rotate crops. Be sure transplants are not diseased. Rotate crops regularly. Solarize the soil in late spring or summer. Black scurf is resting spores; peel away spores before using the potato.
27. Irregular black and brown spots
These appear on lower leaves and stem; leaves turn yellow to brown; tubers may have brown, corky, dry spots. Early blight is a fungal disease spread by heavy rainfall and warm temperatures. It is seen near the end of the season when vines near maturity. Keep weeds down in the field area; they harbor fungal spores. Destroy infected plants. Avoid overhead watering.
28. Leaves yellow between veins and leaves curl upward
shoot tips are stunted; cut stems reveal a white ooze; cut tubers reveal a yellow to light brown ring of decay. Bacterial ring rot. Discard all infected tubers and plants. Plant certified seed stock; plant whole small potatoes instead of seed potatoes. Practice crop rotation. Plant resistant varieties: Merrimack, Saranac, Teton.
29. Rough, scabby or corky spots on surface of tubers
Scab is caused by soilborne bacterium. Disease can be cosmetic. Modify soil to a pH of 4.8 to 5.2; work sulfur into the soil to make it slightly acid and reduce disease. Plant resistant varieties: Alamo, Arenac, Cherokee. If scab occurs, change varieties next year. Use long rotations.
30. Green tubers
Tubers have been exposed to the sun during growing or after digging; sun causes tubers to form chlorophyll green spots. Keep growing tubers covered with soil. Do not eat green sections of potato tubers they contain toxins; cut away the green sections before using. Store potatoes in complete darkness.
31. Tubers are knobby-shaped
Inconsistent moisture, erratic watering, alternating wet and dry conditions. Tuber growth is uneven. Keep soil evenly, moist. Slow, deep water for 2 to 3 hours; do not water again until the soil has dried to a depth of 4 to 8 inches. Mulch to conserve soil moisture. Plant potatoes closer together. Avoid planting knobby varieties.
32. Cavities at the center of the potato, hollow center
Hollow heart occurs when potatoes grow too fast because as a result of too much water or too much fertilizer. Cavity can be discolored and lined with powdery decay, verticillium fungus. Cut away the brown areas before using. Fertilize plants early when tubers are about to form. Avoid planting varieties that develop hollow heart: Chippewa, Katahdin, Mohawk, Irish Cobbler, Sequoia, Russet, White Rose.
33. Large shallow hole in tubers
Grayish white grub is the larvae of the Japanese beetle, a shiny metallic green, copper winged beetle to 1.5 cm long. Grubs feed on potato tubers. Cut away damaged areas and use the rest of the tuber. Handpick grubs and beetles. Use pheromone traps to control beetles. Spray with pyrethrum or rotenone.
34. Rotten tubers
Bacterial soft rot enters tubers wounded by tools insects or disease. The vascular bundles in leaves, stems, and tubers turn black and bad smelling. Rot can not be cured. Plant potatoes in well-drained soil. Remove and destroy infected tubers. Remove all plants and plant debris at the end of the season. Promote good drainage by adding aged compost and organic materials to planting beds. Avoid over-head watering. Rotate crops.
Sulfur applied to the field may reduce rots. Protect tubers from injury.