16 The Colorado Experiment Station. 
vae soon appear as very small white worm-like bodies on the 
potatoes or underground stems. These larvae are slender and 
from an. eighth to one-fourth of an inch long. If tubers are care¬ 
fully taken from the soil early in the season where these insects 
are prevalent, the larvae may be found burrowing into the tuber 
about one-third of the body being inside. At a casual glance 
they appear not unlike short root hairs growing from the surface. 
The injury caused by this insect produces the pimply effect so 
often seen in potatoes on the market and is often confused with 
or may be classed as one of the forms of scab. No practical re¬ 
medy is known for this insect in this state. Spraying with Bor¬ 
deaux mixture and arsenites destroyes or repells them but the ex¬ 
pense of application of this remedy prohibits its use under the 
system of growing used here. When potato planting is delayed 
till June first, the injury to the foliage is avoided to some extent- 
for by the time the plants are up the insects have sought other 
feeding grounds. 
This insect is quite generally distributed over the country 
but is more prevalent in some places than in others and is also 
more numerous some seasons than others. The past season they 
have been particularly numerous, probably owing to the preceed- 
ing mild winter. 
Not infrequently scabby or injured potatoes are infested with 
numerous small white worms so that there is quite a general 
opinion that the scabbiness or injury is caused by them. This is 
not usually the case. The injury or scab is caused by some other 
agent and the worms, which are saprophitic, work in the dead tissue 
and by so doing are credited with the damage. When earth worms 
are particularly plentiful the potatoes may be made dirty as a re¬ 
sult of the worms crawling over them and leaving a slime to 
which the soil sticks. 
Fungous Diseases. The fungous diseases of Colorado potatoes 
differ widely from those which cause the serious losses of the East. 
Early blight (alternaria) can be found but so far as is known little 
or no damage has resulted from it. The late blight (Phytophthora 
infestans) has never appeared at all. 
Corticium Vagum B. & C. (Rhizocionid ). The serious fun¬ 
gous pests of Colorado are mostly those that work below ground. 
Bulletins Numbers 70 and 91 by F. M. Rolfs describe the one fun¬ 
gous disease that causes most of the loss to potato growers of 
this state. This disease evidently is not new to this locality for 
Boyd in his History of Greeley in speaking of the potato industry 
during the Seventies says: “For the first two years potatoes did 
well near Greeley on this side of the river. For some twelve years 
none could be raised in and around town. They did, as a rule, 
