CAUSE: 
Angular leaf spot is caused by Bacterium lachrymans. It lives over the winter on the surface of the seed or 
in the diseased plants about the field. Frequent rains accompanied by rather high temperatures are optimum con¬ 
ditions for the growth of the bacterium. 
CONTROL: 
Spraying, as outlined for the control of Anthracnose, and also dusting are effective. Seed treatment and 
crop rotation are preventive measures. 
FUSARIUM WILT 
Fusarium Wilt first received serious consideration about 1900. It is extremely serious in many parts of the 
country and is most destructive to watermelons, and possibly squash, while most of the other cucurbits show 
marked resistance. The disease enters the plant through the roots and is destructive to the seedlings or to the 
plant at any stages of its growth. The infected plant may die suddenly or it may remain alive indefinitely in a 
dwarfed condition. 
CAUSE: 
A soil organism known as Fusarium niveum which may exist in the soil for many years even though the 
host is absent and may be disseminated by the seed themselves. Presence of the wilt disease may be determined 
by breaking and examining the root of an infected plant. In the case of watennelons, the diseased portion with¬ 
in the root will be of a brownish color. 
CONTROL: 
Seed treatment with corrosive sublimate is a control measure to prevent the spread of this disease. As the 
organism can exist indefinitely both on the seed and in the soil, crop rotation over ten to fifteen year periods is 
necessary. Watermelons cannot usually be grown on the field within this length of time. Fortunately, resistant 
strains of watermelons have been developed which have proven their ability to withstand the most seriously infested 
soil conditions. The Iowa Experiment Station has released a number of kinds, the best of which at this time are 
Improved Kleckley Sweet No. 6 and Improved Stone Mountain No. 5. The University of California College of 
Agriculture has developed the California Klondike R 7 which shows immunity to a high degree. Other recent in¬ 
troductions in watermelon have also proven desirable. 
POWDERY MILDEW 
This form of Mildew was first reported in America about 1890 and is common wherever the host plants 
are grown. The disease is seldom of economic importance under field culture except in localities where extreme 
humidity exists. Irrigation and heavy dews, with the lack of drying winds contribute to its spread. It affects 
all of the cucurbits to a certain degree. Mildew resistant cantaloupes, capable of withstanding the disease, have 
now been developed for the important shipping sections. 
CAUSE: 
The most common fungi responsible for Powdery Mildew are known as Erysiphe cichoracearum. It appears 
as a talcum like growth on the surface of the plant resulting in brown, dried spots which eventually die in severe 
cases. When the entire foliage of the plant is affected it turns to a yellowish color and the fruits become of in¬ 
ferior quality. 
CONTROL: 
The parasite is able to live over the winter on parts of the infected plant. Plowing under or destruction of 
diseased plants is a control measure. Spraying and dusting as recommended for previous diseases are effective 
in eradicating the fungus. It can be controlled in a closed greenhouse by the fumes of a heated pot of sulphur 
or by dusting with sulphur. Resistant varieties have proven highly satisfactory. Hales Best No. 45 is the stand¬ 
ard resistant strain among cantaloupes. 
ONE HUNDRED FORTY-FIVE 
