STUDIES OF HEALTH 
IN POTATOES 
By C. L. [FITCH 
In July and August of 1911 it became apparent that every 
potato plant in the fields attacked, and nearly every field in two of 
the great potato-producing regions of Colorado', had been crippled 
by the leaf-roll disease. One of these regions was on the plains and 
subject to very warm and continuous sunshine. The growers of the 
other district had been purchasing most of their seed potatoes from 
the first region and their potato fields were subject to considerable 
soakage, due to their system of irrigating by filling the subsoil with 
water to such a level that the roots were supplied with moisture by 
capilarity. At the same time the crops of potatoes on the mountain 
mesas throughout the State, even when grown from the same seed, 
were excellent. 
The growers in the first region, the Greeley district, had been 
unable for years to grow their own seed potatoes for more than one 
or two propagations and had drawn upon unirrigated regions for 
their foundation seed supply. For a considerable number of years 
it had been increasingly difficult to produce tubers of the most desir¬ 
able shape. While formerly, the second crop of potatoes had been 
the better because of the improved condition of the soil, at this time 
the second crop had become very much poorer in quality and less in 
quantity, and that, in spite of increasing average yields of grain upon 
the same fields. 
In the second region, the San Luis Valley, seed stocks l?ad been 
maintained more easily, but better results had been secured from 
small whole potatoes such as were readily obtained from the Greeley 
district, and of late years the Valley had used such seed for most ol 
its potato fields. 
A careful study, at the weather bureau in Denver, of the tem¬ 
peratures throughout the year, and other years, for the stations 
nearest to afflicted and to healthy potato regions, and of the rainfall, 
lead to the belief that the factors controlling the appearance of the 
leaf-roll disease were none other than soil-heat and soakage. Where 
the fields had been unusually warm and wet the disease had come; 
where the soil had been cool and not over-wet the plants had 
been healthy. 
A careful field study of potato roots during midsummer re- . 
vealed the fact that in the warmer regions tlie roots within six inches 
