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Symptoms of nutrient imbalance of potato plants

Potatoes grow best in soils of pH 5.0 to 7.0. Deficiencies or toxicities of major or minor elements may be caused by excessive solubility or fixation in the soil through interaction with soil colloids or chemicals.

Nitrogen (N) requirements increase rapidly with potatoes plants growth.
When N is translocated to upper leaves excessively from the lower leaves, they then become yellow.

Later, if the deficiency is not corrected by fertilization, the entire potato plant becomes yellow and fails to grow properly.

Severity of plant response depends on the level of N deficiency. N toxicity from ammonium or nitrites may follow degradation of nitrogencontaining fertilizers in certain soil conditions.

Potato-imbalancePhosphorus (P) deficiency follows P fixation in a wide range of soil types.

Symptoms include retardation in growth of terminals; small, spindly, somewhat rigid plants with crinkled or cup-shaped leaves; darker than normal colour; possibly a delay in maturity; and reduced yield.

Potatoes tubers may have internal rusty brown necrotic flecks similar to internal heat necrosis.
Because P is frequently fixed in the soil, fertilizer banding applications lateral to the seed piece are superior to broadcasting.
Potassium (K) deficiency is common in light, easily leached soils.

Early symptoms are dark or bluish green glossy foliage.
Later, older leaves of potatoes plants become bronzed and necrotic (superficially resembling early blight), and senesce early.
Necrotic, somewhat sunken corky lesions form on the tuber surface, particularly at the stolon attachment.
Potatoes tubers are predisposed to black spot, and when cooked tend to darken.

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Purple Top Wilt

leafhopper(Aster Yellows, Stolbur, Haywire) These diseases, caused by mycoplasma-like organisms that resemble bacteria that lack a cell wall and are thus of indefinite shape, can severely affect yield and tuber sprouting and quality. They are transmitted by leafhoppers.

Symptoms of Purple Top Wilt
Symptoms of Purple Top Wilt include development of shoots and/or aerial tubers in leaf axils.
Potatoes plants become stunted and apical leaves may curl and turn yellowish or purplish. Plants may wilt.
Potatoes tubers from infected plants do not sprout normally.

They are often small, flaccid, malformed, and without sprouts or with thin “hair sprouts”.
Witches’-broom is a symptom caused by another strain of mycoplasma.

Although these diseases are usually of minor importance in potato, being current-season problems only, hundreds of species of vegetable, ornamental, and field crop plants and weeds are susceptible to them.

Management

Leafhoppers cannot acquire the pathogen from potato, and they can be partly controlled by killing weed hosts from which these vectors move to the potato crop.

Leafhoppers can often be avoided by planting later in the growing season after their migration has ended.
The principal leafhopper vectors develop on convolvulaceous weeds, grasses, and small grains.

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Mosaics

(PVX, PVS, PVM, also PVY and PVA)

Mosaic symptoms may be caused in potato leaves by several different viruses, singly or in combination.
mosaicsSome of these are potato virus X (PVX), potato virus S (PVS), and potato virus M (PVM), as well as PVY and PVA.
PVX may cause yield losses above 10%, with the extent varying according to strain and potato cultivar.

It is transmitted through infected tubers and by contact (not by aphids), and normally causes mosaic.

Infection may be mild in some cultivars and is frequently latent. Virulent strains may cause crinkling. Some cultivars are hypersensitive to certain strains and react with top necrosis.
PVS is common and may cause mild symptoms.

It has little effect on yield. It is transmitted through infected tubers, by contact, and by aphids in some strains.
Infection is normally latent although some cultivars react with mild mosaic or faint vein banding.
A few sensitive potatoes cultivars react with severe bronzing, necrotic spotting, or even leaf drop.
PVM is less common than PVY, PVX, or PVS, and little is known about its effects on yield. It is perpetuated by infected tubers and transmitted by contact and by aphids.
The virus is latent in some potatoes cultivars although in others it causes a mild mosaic or even a severe mosaic and leaf crinkle.
Under certain environmental conditions, sensitive cultivars may also develop necrosis of petioles and leaf veins.

Management of Mosaics potato disease

PVX, PVS, and PVM are controlled by clonal selection during seed multiplication. Roguing is useful only when obvious symptoms develop.
Cultivars resistant to PVX for growing potatoes are available.

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