the most serious disease affecting the Cucurbits. Cucumber, Summer Squash, and Muskmelon are the most sus¬ 
ceptible. A number of wild plants serve as hosts and are responsible for the spread of the inoculum. 
SYMPTONS: 
It is characterized by a dwarfing of the plant, mottling, yellowing and wrinkling of the leaves and warting, 
curling, and mottling of the fruits. 
CAUSE: 
The cause is undetermined but the trouble is very infectious. Juice from affected plants produces the disease 
in healthy ones when inoculated into them by an agent. Among the most common host plants are wild cucumber, 
milkweed, poke weed, ground cherry, and catnip. It over-winters in their roots or seed and is carried to cultivat¬ 
ed crops in the spring by insects, chiefly by the cucumber beetles and plant aphids. 
CONTROL: 
The thorough eradication of wild host plants around the fields, combined with rigid insect control measures 
have proven successful in controlling Mosaic. Important progress has been made in the development of Cucum¬ 
ber varieties capable of withstanding this disease. 
ANTHRACNOSE 
No disease of Cucurbits is more destructive than Anthracnose. It has been known for more than fifty years 
and is common in every country where cucurbits are grown. In many markets it is difficult to find Watermelons 
or Muskmelons that do not show at least a few spots. Watermelon are most severely infected but the disease 
often appears in epidemic form on Cucumber and Muskmelons, as well as the other cucurbits, in a lesser degree. 
Varietal susceptibility to this disease is quite noticeable, however. 
SYMPTONS: 
Any portion of the plant above ground may be affected. The spots on the foliage begin as small yellowish 
water soaked areas which enlarge rapidly and turn brown in most cucurbits. In the case of Watermelon, they 
become black. These spots are about one-fourth to one-half inch in diameter on the leaves and appear as elon¬ 
gated sunken lesions on the stems. The young fruits may darken, shrivel and die. On Watermelons the spots 
vary from one-fourth inch to two inches in diameter and appear as black sunken cankers. When moisture is 
present the dark center of the lesion is covered with a gelatinous mass of salmon-colored spores. 
CAUSE: 
The most commonly used term for this fungi is Colletotrichum lagenarium. The disease remains alive in 
the old dead tissue in the soil at least one winter as well as in the seed themselves. The young plant may be¬ 
come inoculated at any stage of growth by the various distributing agencies. The fungus becomes epidemic us¬ 
ually during excessive rainfall, although it requires relatively high temperatures, growing best at 75 degrees F. 
CONTROL: 
As the pathogene lives over for at least one season in the soil, a two year crop rotation is essential. Treat¬ 
ment of the seed with corrosive sublimate as outlined under (Seed Treatment) is a preventative. Infection in 
the field can be avoided by spraying with bordeaux. 
ANGULAR LEAF SPOT 
The disease was first discovered about 1905 and is serious only to Cucumber. 
SYMPTONS: 
It attacks particularly the leaves, causing angular water-soaked spots one-sixteenth to one-eighth of an inch 
across, d he water-soaked area later turns gray, dies and often drops out. The spots on the fruit are smaller in 
size and circular in shape. When the diseased portion becomes white and cracks open it permits the entrance of 
soft-rot organisms, which will often cause decay of the entire fruit. 
ONE HUNDRED FORTY-FOUR 
