352 
while on a large number of farms one or two 
infested fields are being rested from potatoes 
and the directed acreage is being grown on 
the remaining land by more intensive crop- 
ping, * *. * 
No information is available concerning the 
total acreage of infested land that is being 
cropped after being rested, but it can be 
stated that 25 percent of the failures occurred 
on such land because the resting period had 
been too short. In some instances farmers 
had concluded that a rest of 3 years ought to 
be sufficient, in others they had had a good 
crop a year or two earlier after a long rest 
and thought that the pest had been starved 
out. But the most distressing instances were 
the few where the trouble showed up in 
patches after a rest of 7 or 8 years. 
With regard to a remedy, Mr. Wood 
has the following to say: 
Farmers are naturally anxious to learn what 
steps have been taken to discover some means 
of controlling this eelworm, and it may be 
mentioned in this connection that when the 
Holland County Council purchased the Agri- 
cultural Institute Farm they were soon con- 
fronted with this problem at Kirton. No 
time was lost in calling in available specialists 
to carry out an investigation. South Lincoln- 
shire was not the first potato-producing area 
to experience the trouble, but because of the 
importance of potatoes to the county, and the 
fact that a County Advisory Service had re- 
cently been introduced, experiments were 
soon in progress. Hopes of success were high 
when a dressing of drained creosote salts 
applied at the rate of 8 cwts. per acre and 
ploughed in 14 days before planting gave a 
big increase of crop. But after several years 
it became obvious that the treatment was 
unreliable and its recommendation was dis- 
continued. Since then research work has 
continued at the Institute of Agricultural 
Parasitology on fundamental points in the 
life-history and responses of the pest. A vast 
amount of information has been accumulated 
but the search for some material suitable for 
application to the soil still goes on. Mean- 
while the only effective recommendation is 
that of resting the land from potatoes for a 
suitable period. And that suitable period 
has still to be worked out locally. 
In summarizing he points out that— 
There is as yet no instance on record in the 
county where main crop potatoes have been 
grown successfully even once in 4 years when 
a crop has once iailed without the trouble 
again becoming eventually evident. In the 
absence of some helpful control measure it is 
not unlikely that a 6-year rotation will have 
to be adopted. 
ANNUAL REPORT SMITHSONIAN INSTITUTION, 1948 
The following appears in Leaflet No. 
117 published by the Ministry of Agri- 
culture of Northern Ireland in Decem- 
ber 1945: 
Potato root eelworm is now regarded as 
the most serious pest affecting the potato 
crop in many of the main potato-growing 
areas in Great Britain. Because of its slow 
development, its seriousness, and even its 
presence, are often not realized until there 
is a very great reduction in crop yields. The 
pest may be regarded as more serious than 
the well-known Black Scab disease, because 
all varieties of potatoes are subject to attack 
and there is no known cure under field condi- 
tions. Once land becomes infected it remains 
so for a long period. How long is not known. 
The first symptoms of eelworm attack are 
the appearance of a patch or patches in the 
crop where the plants are dwarfed and sickly 
—not unlike a patch produced by a wet spot 
in a field or even by other diseases. ‘The 
plants have weak, spindly stems, and the tops 
are generally stunted and paler in color than 
those of the rest of the crop. The leaves are 
under-sized and have a tendency to wilt and 
to drop off prematurely. The lower leaves 
wither at first but the whole top eventually 
collapses early in the season. As these plants 
die off, the attack spreads to the healthier 
plants around the margins. 
The author has the following to say 
in regard to preventive measures: 
There is no effective means of destroying 
the eggs of the eelworm in the fiedd and it is, 
therefore, of the utmost importance that 
everything possible should be done to prevent 
clean land from becoming infected. Two 
essentials toward this end are (a) to use only 
certified eelworm-free seed, and (b) to adopt 
a wide rotation on the farm in which potatoes 
do not occur more than once every 5 years. 
Eelworm attack nearly always occurs when 
potatoes are grown frequently in the same 
field. Farmers should, therefore, avoid this 
practice at all costs, even should this mean 
limiting their area under potatoes. 
It has been clearly demonstrated 
that golden nematode cysts will re- 
main in the soil for 8 or more years 
without the presence of host plants. 
Therefore, any natural or mechanical 
movement of soil from infested fields 
during that time may result in its 
spread to new areas. Soil fumigation 
with materials now available will sub- 
stantially reduce but not eradicate 
infestation and such treatment is costly 
and provides only temporary relief. 
