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Problem Solver Plant Marquee

Plant:

Potatoes
Image of Potatoes
Adaptation
Throughout the United States.
Planting Method
Plant 11/2- to 2-ounce seed pieces about the size of a medium egg) in trenches 3 to 4 inches deep. Allow 12 to 18 inches between pieces. Plant pieces whole or cut, with at least one eye on each piece. Purchase new seed pieces each year.
Soil
Any good garden soil that is rich in organic matter.
Water
Water about an inch a week to keep the soil moist.
Storage
Cure in the dark for 1 week at 70&deg;F and high humidity. Then store in a humid area at between 40&deg; and 50&deg;F until ready to use. Avoid storing in the refrigerator; it converts starch to sugar, making potatoes turn dark when cooked.
Fertilizer
At planting time, fertilize with a continuous-rease plant food for vegetables.
Harvest
Dig potatoes carefully with a spade or pitchfork so as not to wound the tubers. Dig as needed 2 to 3 weeks after flowering, If storing, dig after tops turn yellow and die.
Related problems

Colorado Potato Beetle -

Image of Colorado Potato Beetle
Colorado Potato Beetle

Common Scab -

Image of Common Scab
Common Scab

Early Blight - Potatoes

Image of Early Blight - Potatoes
Early Blight

Flea Beetles - Potatoes

Image of Flea Beetles - Potatoes
Flea Beetles

Late Blight -

Image of Late Blight
Late Blight

Potato Leafhopper -

Image of Potato Leafhopper
Potato Leafhopper
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Colorado Potato Beetle -

Image of Colorado Potato Beetle
Colorado Potato Beetle
Description
Yellow-orange beetles, about 3/8 inch long with black stripes, are eating the leaves on potato plants. Fat, red, humpbacked larvae with two rows of black dots may also be present.
Analysis

Leptinotarsa decemlineata This insect pest, also known as the potato bug, often devastates potato, tomato, eggplant, and pepper plantings. Both adults and larvae damage plants by devouring leaves and stems, damaging small plants most severely. The beetle was originally native to the Rocky Mountains and spread eastward in the late 1800s as potato plantings increased. It is now found in all states except California and Nevada. In some areas of the country, the beetle population may reach epidemic proportions. The beetles lay their yellow-orange eggs on the undersides of leaves as the first potatoes emerge from the ground in the spring. The larvae that hatch from these eggs feed for 2 to 3 weeks, pupate in the soil, and emerge 1 to 2 weeks later as adults, which lay more eggs. One generation is completed in a month. Depending on the area, there are one to three generations per year.

Solution

Potato beetles are becoming increasingly resistant to insecticides, so control may be difficult. Floating row covers help keep beetles away from potatoes. Resistant varieties of potatoes are being developed.

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Common Scab -

Image of Common Scab
Common Scab
Description
Brown corky scabs or pits occur on potato tubers. Spots enlarge and merge together, sometimes covering most of the tuber. Leaves and stems are not affected.
Analysis

This plant disease is caused by a bacterium (Streptomyces scabies) that persists in the soil for long periods of time. Besides potatoes, scab also infects beets, carrots, and parsnips. The disease affects only the tubers, not the leaves or stems. Bacteria spend winter in the soil and in infected tubers left in the garden. Infection enters through wounds and through the breathing pores in tuber skins when the young tubers are growing rapidly. Scab is most severe in warm (75&deg; to 85&deg;F), dry soil with a pH of 5.7 to 8.0. The severity of scab often increases when the pH is raised with lime or wood ashes; it is not a problem in acid soils with a pH of 5.5 or less. Poorly fertilized soil also encourages scab. The bacteria withstand temperature and moisture extremes, even passing intact through the digestive tracts of animals-manure can spread the disease. Tubers infected with scab are edible, but much may be wasted as the blemishes are removed.

Solution

Keep the soil moist for 1 to 2 months after tuber set. Avoid using materials such as wood ashes and lime. Do not use manure on potatoes. Plant potatoes in the same area only once every 3 to 4 years. Use certified seed pieces that are resistant to scab.

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Early Blight - Potatoes

Image of Early Blight - Potatoes
Early Blight
Description
Irregular dark brown to black spots, 1/8 to 1/2 inch in diameter, appear on the lower leaves. Concentric rings develop in the spots, which enlarge, causing the leaf to die and fall off. Tubers may develop dark, sunken spots, often with a purplish raised border.
Analysis

This plant disease is caused by a fungus (Alternaria solani) that attacks both vines and tubers. The same fungus causes early blight of tomatoes. It is most severe toward the end of the growing season when the vines approach maturity and after tubers are formed. Many leaves may be killed. The potato yield is reduced, but the plant seldom dies. Tubers are frequently infected through wounds inflicted during harvest. Early blight is favored by alternating periods of wet and dry weather and by temperatures from 65&deg; to 85&deg;F. The fungal spores spend the winter in plant debris left in the garden. Infected tubers are inedible.

Solution

Clean up and destroy plant debris after harvest. Do not store infected tubers. Avoid overhead watering by using drip or furrow irrigation. Plant certified, disease-free seed pieces. Apply a fungicide labeled for this disease, following label directions.

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Ortho® MAX® Garden Disease Control Concentrate

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Flea Beetles - Potatoes

Image of Flea Beetles - Potatoes
Flea Beetles
Description
Leaves are riddled with shot holes about 1/8 inch in diameter. Tiny, black beetles jump like fleas when disturbed. Seedling leaves and eventually whole plants may wilt and die.
Analysis

These beetles jump like fleas but are not related to fleas. Both adult and immature flea beetles feed on a wide variety of garden vegetables, including potatoes. The immature beetle, a legless gray grub, injures plants by feeding on the roots and the lower surfaces of leaves. Adults chew holes in leaves, feeding for up to two months. Flea beetles damage young plants most. Adult beetles survive the winter in soil and garden debris. They emerge in early spring to feed on weeds until potatoes sprout. Grubs hatch from eggs laid in the soil and feed for 2 to 3 weeks, damaging the tubers. After pupating in the soil, they emerge as adults to repeat the cycle. One to four generations occur per year.

Solution

Apply an insecticide labeled for this pest, following label directions. Watch new growth for evidence of further damage. Clean all plant debris from the garden after harvesting to eliminate spots for adult beetles to overwinter.

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Ortho® MAX® Malathion Insect Spray Concentrate

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Late Blight -

Image of Late Blight
Late Blight
Description
Brownish water-soaked spots appear on leaves. They enlarge rapidly, turn black, and kill the leaves, then the leafstalks and main stems. In moist weather, gray mildew grows on the lower surfaces of leaves. Both in the ground or in storage, brownish purple spots that become a wet or dry rot infect the tuber skins.
Analysis

This plant disease is caused by a fungus (Phytophthora infestans) that seriously injures potatoes and tomatoes. The disease was responsible for the great potato famine in Ireland from 1845 to 1850 and is the most important disease of potatoes worldwide. The fungus spreads very rapidly, killing an entire planting in a few days. Infected tubers are inedible. Tubers are infected when spores wash off the leaves and into the soil, or they may be attacked during harvest and rot in storage. A soft rot often invades the damaged tubers. Late blight is prevalent in moist, humid weather with cool nights and warm days. Foggy, misty weather and heavy dew provide enough moisture for infection. Spores survive the winter in infected tubers in the garden or compost pile.

Solution

If late blight is an annual problem in your area, apply a fungicide labeled for this disease, following label directions. Use drip or furrow irrigation. Wait at least a week after plants die naturally before digging the tubers. This allows time for the spores to die. Handle the tubers gently to avoid wounding them. Clean up and destroy plant debris after harvest. Plant certified disease-free seed pieces.

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Ortho® MAX® Garden Disease Control Concentrate

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Potato Leafhopper -

Image of Potato Leafhopper
Potato Leafhopper
Description
Spotted, pale green insects up to 1/8 inch long hop, run sideways, or fly away quickly when a plant is touched. The leaves are stippled or appear scorched, with a green midrib and brown edges that are curled under.
Analysis

Empoasca fabae This insect feeds on potatoes and beans and on some fruit and ornamental trees. It sucks plant sap from the undersides of leaves, causing leaf stippling. This leafhopper is responsible for hopperburn and the browning and curling of the edges of potato leaves. The leafhopper injects toxic saliva into the nutrient-conducting tissue, interrupting the flow of food within the plant. Potato yields may be reduced drastically by hopperburn. Leafhoppers at all stages of maturity are active during the growing season. Both early and late varieties of potatoes are infested. Leafhoppers live year-round in the Gulf states and migrate northward on warm spring winds-even areas that have winters so cold that the eggs cannot survive may be infested.

Solution

Apply an insecticide labeled for this pest, following label directions. Remove nearby weeds that may harbor leafhopper eggs.

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