MISSOURI BOTANICAL GARDEN BULLETIN 69 
sugar, hence deteriorates in quality, so that every second or 
third year they send to Maine or some of the adjoining states 
for their seed supply. There is no encouragement for the 
grower to build up his seed stock on this basis, and herein lies 
another interesting and important problem in plant breeding, 
and also one of considerable economic importance. 
In southeastern Iowa the Heinz Company and others grow 
a considerable acreage of cabbage and other truck crops. The 
production of cabbage has gradually declined, due to the fact 
that the soil has become infected with cabbage yellows. This 
disease has become so serious that hundreds of acres have had 
to be abandoned for cabbage purposes. Steps are now under 
way toward the breeding and selection of a disease-resistant 
strain adapted to this region, and the results so far obtained 
are very encouraging. Indications are that through this 
means a large acreage can be reclaimed for cabbage growing. 
Particularly in the case of the orchard fruits, there are a 
number of insect and other diseases of economic importance. 
The loss to the grower from these is considerable, and with the 
rapid increase in the price of land, the problem of heading off 
these leaks becomes all the more urgent. Within the last few 
years, for example, the Illinois canker disease has spread rap- 
idly over the southern and western parts of the state. A field 
study has brought out the fact that the Ben Davis is a 
particularly susceptible variety. The apple scab is also very 
destructive some years, and in 1915, in some instances 
where this fruit had not been sprayed, it was not worth 
gathering. In a spraying experiment, conducted by the 
department for the control of this disease, three applica- 
tions, one of Bordeaux and two of lime sulphur, gave 12 per 
cent of scabby fruit, while the unsprayed plot showed 80 per 
cent infected. For the one lot, the grower received seventy- 
five cents a bushel and for the other twenty-five cents. 
There are also a number of interesting problems dealing 
with cultural methods as they affect the yield, returns, and 
quality of the product. In the case of the potato, for ex- 
ample, there has been under way, for a number of years, an 
experiment to determine the best time for planting late pota- 
toes. Plots have been planted each year at ten-day intervals, 
and the time of planting correlated with soil temperature and 
atmospheric conditions. In the year 1915, for example, the 
early planted plots yielded upwards of 300 bushels an acre, 
and the late plantings 70, the difference being due largely per- 
haps to an outbreak of the late blight which struck the later 
plantings at a critical period of their development. 
During the heated period the soil temperature runs very 
high and is thought to be one of the limiting factors in potato 
