70 
CoLOKADO Experiment Station 
To control the disease take good care of young trees by supply- 
ing sufficient moisture and avoiding mechanical injuries. If the 
tree is already infected it may often be saved by pruning out and 
destroying all diseased twigs and cankers, and painting over the 
wounds with shellac or coal tar. 
Since the .disease is known to occur in nurseries, all nursery 
stock should be inspected and any diseased stock destroyed. 
POTATO 
Fusarium Blight (Fusarium spp.) (69), (72)— Fusarium blight is 
common throughout Colorado, but is especially severe in the Greeley 
district. It is perhaps the most destructive disease of the potato in 
the state. It has been estimated that in 1917 there was a loss of 500,- 
000 bushels in Colorado due to this disease. 
The disease manifests itself first by a wilting and a rolling of the 
leaves followed in severe cases by a premature death of the remain- 
der of the plant. On examination of diseased plants, the seed piece 
is found to be rotted and in later stages the roots and stem may also 
show signs of decay. 
Fusarium blight is caused by fungus which lives in the soil and 
infects the seed piece and spreads from there into the stem and 
roots killing or seriously injuring the plant. 
No thoroughly effective methods of control are known but the 
planting of whole potatoes for seed, combined with judicious irriga- 
tion and other cultural practices are perhaps the most effective 
measures. An excess of moisture should always be avoided. A long 
rotation raising other crops followed by alfalfa is also very 
beneficial. 
Black Leg (Bacillus atrosepticus) (69), (70), (71), (72) — Black 
leg occurs in Colorado, but is not responsible for any great loss. The 
disease occurs on both vines and tubers causing an inky black dis- 
coloration near the ground line. The entire plant becomes yellov , 
wilts, and dies. The seed piece is nearly always rotted. New tubers 
may often become infected in the field and later develop a soft lot 
in storage. 
Black-leg is caused by bacteria that live from year to year in 
partly rotted tubers. The organism probably does not live in the 
soil for a A^ery long time. 
A seed piece showing any signs of decay should never be planted. 
Puring the growing season all diseased plants should be pulled u]) 
