Biology Reference
In-Depth Information
isolate seed plots. Varieties Katahdin, Chippewa,
Houma and Sebago are resistant.
Potato S Carlavirus
Generally symptomless in most potato cultivars.
Potato Green Dwarf
Potato Spindle Tuber Viroid
Caused by a strain of Beet Curly Top
Hybrigeminivirus. Terminal growth is dwarfed
and deformed; leaflets cupped upward.
General on all tested varieties of potatoes. Plants
are more erect than normal but spindly, lacking
vigor. Stems are stiff, leaves small, dark green;
tubers are elongated, pointed at the end, the eyes
“staring”. Symptoms are accentuated by high soil
moistures. Transmission is by contaminated
knives in cutting, by contact between freshly cut
seed pieces. Control by using certified seed.
Potato Leaf Roll Luteovirus
Important wherever potatoes are grown. Symp-
toms show about a month after plants appear
above ground. Leaves are thick, leathery, rolled,
with excessive starch; sometimes with a reddish
or purple discoloration on the underside. Plants
are dwarfed; tubers are few, crisp, with net
necrosis - brown strands of dead tissue - in
some varieties; sprouts are spindling; yield may
be reduced one-half. Transmission is by peach
and other aphids.
Use certified seed potatoes. These come from
a foundation stock obtained by indexing.
Seedpieces or tubers are planted consecutively
in a row, and if any show virus symptoms, the
whole unit is destroyed.
Potato Vein Banding ¼ Potato
Y Potyvirus
On potato and many other hosts, transmitted
mechanically and by many aphids. On some vari-
eties there is leaf drop and necrotic streak or chlo-
rotic mottling; on others there is no sign of disease.
Potato Virus A
Present in nearly symptomless form in some vari-
eties, causing crinkle with virus X.
Potato Leaf Rolling Mosaic
¼
Potato
M Carlavirus
Potato X Potexvirus
Leaves are mottled, flaccid, with some upward
rolling but without distinct rolling, rigidity of leaf
roll. Transmission by peach, potato and geranium
aphids.
Almost universally present in commercial potato
stocks. Cause of latent mosaic.
Potato Mottle
Potato Witches' Broom
Caused by potato X potexvirus.
Apical leaves are slightly rolled, upright, light
green with reddish or yellowing margins.
There is proliferation of axial buds with tendency
to bloom and set fruit; there are aerial tubers
and numerous small subterranean tubers. Such
tubers put out spindle shoots without a rest
period and produce dwarfed, very bushy plants
Potato Rugose Mosaic
Caused by potato Y potyvirus, often with PVX.
Leaves are crinkled, mottled; lower leaves with
black veins; plants are stunted, die prematurely.
Control by careful roguing.
