Compendium of Potato Diseases - (PDF, 101 mb) - USAID
Compendium of Potato Diseases - (PDF, 101 mb) - USAID
Compendium of Potato Diseases - (PDF, 101 mb) - USAID
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sevrit<strong>of</strong> stnting, chiorosis. loss <strong>of</strong>' lower leaves, and vied<br />
reduction,<br />
Speckle leaf'. brown to black spots about I mm in diameter<br />
that may coalesce on lower leaves <strong>of</strong> some early cultivars. is<br />
particularly severe ollos ing heavy rainfall or irrigation and is<br />
alleviated by nitrogen side dress.<br />
When N toxicity occrs.iCiclds arc reduced: root de\ehlptiicnt C'<br />
is poor: and lea\es may roll upward or be deforned as "mouse<br />
ear.- N toxicity can result from the forn <strong>of</strong> N available to the<br />
plant. Alnmonil illd or nitrites formed Iromii urea and<br />
dianmroniuni phosphates are toxic. Incertain soil conditions,<br />
principally \,er acid soils. conversion <strong>of</strong> amlnoniuni nitrogen to<br />
nitrate nitrogen is i paired. In nutritional leafroll, nitrate<br />
nitrogen is insufficient to balance ainotherwise normal amount Fig. 29. Potassium deficiency symptoms on tubers.<br />
ot annioniur<br />
Note corky<br />
nitrogen a\ailable to tie plant, sunken areas at stolon end. (Courtesy W. M.Laughlin)<br />
Surf'ace applications <strong>of</strong> urea. esrecially when banded tihigh<br />
rates. can cause damage from ammonia \olatiliiation. 1Burning<br />
<strong>of</strong> leaves and stem lesions de\elopi ng near urea pellets are due to green spots (approximately I mm in diameter) appear between<br />
am monia \olatili/ation and not to an osmotic or salt effect, veins <strong>of</strong> larger leaflets, rese<strong>mb</strong>ling mild mosiac. When K is in<br />
relatively short supply, older leaves first become bronzed, then<br />
Selected References necrotic (Plate 9). and senesce early. Leaflet margins from the<br />
middle to the top <strong>of</strong> the plant roll<br />
NIItN(iIR.I<br />
upward. l.eaflets are small,<br />
1). R. IOt'll)l Nand E. I). JONES. 1978. <strong>Potato</strong> cupped, crowded together,<br />
ield<br />
crinkled,<br />
reductions<br />
and<br />
associated<br />
bronzed on<br />
\%ith<br />
the<br />
certain<br />
upper<br />
fertiliier mixtures. Am. surface. The overall bronzed<br />
Ilotarn<br />
effect<br />
.I. 55:227-234.<br />
<strong>of</strong> the foliage is<br />
predominant, leaves frequently<br />
VI ;OSL<br />
have dark<br />
I. I...<br />
brown<br />
and<br />
specks<br />
R. W.('IIASE.<br />
on the<br />
atfected by fr tier and ,sater manuagement.<br />
1973. Speckle leaf<br />
A m.<br />
<strong>of</strong><br />
<strong>Potato</strong><br />
potato as<br />
.I.<br />
lower<br />
S m<br />
surface,<br />
t m<br />
which<br />
a'<br />
may<br />
d v.<br />
coalesce<br />
rr<br />
and<br />
i<br />
cause<br />
l 'i''<br />
marginal necrosis.<br />
. '<br />
50:311-314.<br />
Phosphorus<br />
Symptoms<br />
bright weather<br />
may develop rapidly<br />
following<br />
within four days during<br />
cloudy, sunny,<br />
rainy periods. Necrosis is<br />
severe and may superficially rese<strong>mb</strong>le early blight. Stalks may<br />
be slender with short internodes. When K is acutely deficient,<br />
P1is essential early in plant growth and later in tuberization.<br />
Early season deficiency retards growth <strong>of</strong> terminals, and plants<br />
are small, spindly, and somewhat rigid. l.eaflets fail to expand<br />
nornially. are crinkled or cup-shaped (Plate 8), darker than<br />
normal. lusterless, and may be scorched at the margins. L.ower<br />
leaves may drop. ILeaflets are not bronzed, leaf petioles are<br />
More erect than normal. Maturity may be delayed.<br />
Roots and stolons are reduced inboth nu<strong>mb</strong>er and length.<br />
lhibers lack external syniptoms. but internal rusty' brown<br />
necrotic flecks or spots are scattered throughout the flesh in<br />
sometimes radial patterns. (See also internal heat necrosis and<br />
calcium deficiency.)<br />
l)eficicncy occurs on a \wide range <strong>of</strong>' soil types: calcareous<br />
Soils. pear or rmuck. light soils with low initial P content, and<br />
heavy soils in sshich P is lixed. Muclh <strong>of</strong> the P is translocated<br />
frorn vines to tubers, and the crop rerioves a considerable<br />
ariount if ' froi the soil. Banding <strong>of</strong> P lateral to the seed piece<br />
decreases P)fixation and improves P uptake over that from<br />
broadcast application. little can be done to alleviate P-<br />
deficiency symptoms during the growing season, although<br />
foliage a pplicatiorns with neutral ammonium phosphate or<br />
polyphosphate<br />
p herevplea are archeful. hielpf'ul, h , e ln ie<br />
Where P levels are vry ig. especially in alkaline soils, the<br />
uptake and or utilization <strong>of</strong>' Zn or Fe may be reduced.<br />
the growing point is affected and general dieback develops.<br />
Plants become short and squatty with shiortened internodes.<br />
They' appear droopy because <strong>of</strong> downward leaf curling.<br />
Roots are poorly developed and stolons ate short. Tuber size<br />
and yield are reduced. Necrotic, brown, sunken lesions develop<br />
at stolon ends <strong>of</strong> tubers <strong>of</strong> plants with necrotic foliage. Later, the<br />
affected tissue dries out, Iortiiing a hollow spot. 2mm or more in<br />
diameter. surrounded by corky tissue (Fig. 29).<br />
K deficiency predisposes to black spot. During early storage,<br />
K-deficient tubers frequently develop brown to black enzymatic<br />
discoloration (f raw cut surfaces on exposure to air.<br />
Discoloration is frequently more severe at the stolon end <strong>of</strong> the<br />
tuber. Tuber flesh also becomes dark after cooking.<br />
K deficiency is most common on light, easily leached, sand,<br />
muck, or peat soils. Exchangeable K should exceed 200 kg/ ha<br />
(178 l b A) in the upper 20 cm <strong>of</strong> soil.<br />
Selected References<br />
BAER UG,R., and R. EN(E. 1974. Influence <strong>of</strong> potassium supply and<br />
s:orage conditions on the discoloration <strong>of</strong> raw and cooked potato<br />
tubers <strong>of</strong> cv. Pimpernell. <strong>Potato</strong> Res. 17:271-282.<br />
FONG, K. It. and A. I.RICl-. 1969. Growing potato plants by the<br />
L.AUGHl.IN, ater culture W. technique. M. 1966. Am.<strong>Potato</strong> Effect <strong>of</strong> soil .1.46:269-272.<br />
applications <strong>of</strong> potassium,<br />
nagnesium sulfate and niagnesi unl sulfate spray on potato yield.<br />
composition and nutrient uptake. Am. <strong>Potato</strong> J. 43:403-411.<br />
Selected References<br />
L.AUGH I.IN, W. M., and C. I. )EARIBORN. 1960. Correction <strong>of</strong> leaf<br />
necrosis <strong>of</strong>potatoes Nitlh foliar and soil applications <strong>of</strong> potassium.<br />
IIA-Rt'(i. R.. and K. SI ENIIERG. 1971. Influence <strong>of</strong> placement<br />
method and vater supply on the uptake <strong>of</strong> phosphorus by earl'<br />
poratoes. <strong>Potato</strong> Res. 14:282-291.<br />
llt)t'(ilI NI). . '. U. 1960. [he influence <strong>of</strong> phosphorus on the<br />
gros, rh and physiology <strong>of</strong> the potato plant. Am. <strong>Potato</strong> .1.<br />
37:127-138.<br />
Am.<strong>Potato</strong> .1.37:1-12.<br />
MUL.) R, . G . 1949. Mineral nutrition in relation to the<br />
biocliemistry and phvsiology <strong>of</strong> potatoes. Plant and Soil 2:59-121.<br />
Calcium<br />
Potassium Ca-deficient plants are spindly, with small, upward rolling,<br />
crinkled leaflets having chlorotic margins that later become<br />
necrotic (Plate 9). In severe deficiency, leaves are wrinkled and<br />
K is essential ftornormal growth and is highly mobile within stem tips cease to funitii. giving a rosette appearance. Root<br />
tIre plant. meristems cease to grew.<br />
Early appearance <strong>of</strong> unusually dark green, bluish green, or Tubers on Ca-deficient plantsdevelop diffuse brown necrosis<br />
glossy foliage is a dependable symptom <strong>of</strong> K deficiency. I.ight in the vascular ring near stolor attachnments, and later similar<br />
23