The Hood River glacier. (Hood River, Or.) 1889-1933, 1921-11-03
MOSAIC OF POTATOES
ATTACKS in WEST

A survey of the western states con-
Quoted during the past summer by
pathologists of the United States De-
partment of Agriculture shows that
unless adequate measures for the elm
ination of the moasic disease of pota-
toes are taken Immediately the work
of potato seed improvement in the
west will soon become extremely diff
cult, if at all possible. The disease
was found attacking Upper Valley po-
tatoes. Being of infectious nature,
the disease is spread in the field
throughout the summer by means of
insects which carry it from diseased to
healthy plants, and is also transmitted
" ith the seed tubers from one gener-
alton to another.
There is no evidence that a plant
once infected can recover and produce
healthy progeny at any time. On
the contrary, the infected plants ordi-
narily tend to a very rapid deteriora-
ton, and under certain environment
conditions practically cease to produce
tubers in the third or fourth generation.
If only a partial wedding out of the
worst cases is practiced, the situation
may be somewhat improved though not
III ali Ch6C6 anu ny LuCdIIB
nently. The mild and the medium
stages of the disease left in the stock
reserve as perpetual sources of infec-
tiOn, and eventually the entire strain
becomes diseased and IS apt to run
out" completely.
1t has been repeatedly demonstrated
in the east that the average reduction
of yield due to mosaic is about 80 per
cent. Precisely the same effect of this
disease was noted in the case of all the
varieties grown in different western
states. Some remarkable instances
were observed during the last two
years of field observations carried on
by the department in which the reduc-
tion of yield in individual hills was in
direct proportion to the severity of the
infection.
The potato acreage in certain irri-
gated sections of the West has been
increased this year by one-third as
compared with that of the last year,
yet the yield in these districts is only
two-thirds of the normal. Many grow
ers complain that where 300 sacks or
more were raised to the acre in former
years, only 100 to $50 sacks are obtain
able now. This is in fields under good
cultural conditions, showing good
stands and a high freedom from
fungus and bacterial diseases. The
low yielding quality of the strains in
question no doubt is principally a man
Hesitation of mosaic. The need of
good seed in the west is we'll recog-
nized and is growing every year, yet
only meager quantity of even rela-
tively good seed is obtainable.
There is very little. if any, hope of
improving badly infected strains of
potatoes, the department specialists
think; therefore, prompt efforts should
be made to locate the most healthy
strains of the various important COM
mercial varieties. Since there is no
means at present of detecting mosaic
on the tuber the search should be con-
fined exclusively to the fields during
the growing season. When the best
strains are found they should further
be improved by the annual elimination
of all the diseased individuals.
1t is necessary to place this work in
charge of highly trained specialists.
since the identification of certain mi
mute and peculiar characters of the
disease requires a considerable exper-
fence and a great deal of pathological
knowledge. Furthermore, manifesto
tions of mosaic under the varied cul-
tural and climatic conditions of the
west are often very obscure and not
yet fully understood.