Plant Diseases 
j 
recent years much thought has been given to plant diseases, especially toward the development of re¬ 
sistance in varieties to some of the most destructive kinds. There are numerous forms of disease and a variety of 
measures must be used in their control. Some are not of sufficient distribution to require serious consideration 
but in all there are about twenty-five kinds more or less harmful to the cucurbits. About nine of these are 
likely the most serious in America and we list them as nearly as possible in the order of their importance. 
In dealing with plant diseases we feel that commendable progress has been made in recent years and yet 
much remains to be done. It is our opinion that this field offers much promise for the near future in the de¬ 
velopment of disease resistant varieties. Further, that the recommendations of our leading growers should be 
carefully considered with a view to giving them our complete cooperataion in the distribution of these new intro¬ 
ductions of proven merit. 
It seems likely that most forms of plant disease can be controlled to some extent by simple precautions, 
such as the disposition of refuse, trash, weeds, etc., from the fields and the proper eradication of host plants 
and insects. Few diseases are actually seed borne among the cucurbits, nevertheless, some of the most danger¬ 
ous kinds are carried on the seeds themselves. The fact that machine harvested seeds are fermented in vats 
where portions of the rind and often vines too are included among the seed is one of the ways that disease germs 
can come into actual contract with the seeds. The washing and curing processes which follow do not entirely 
remove all germs of disease. Hence, seed treatment is now recommended by many authorities to prevent general 
distribution of diseases about the country. It is further protection against plant pests and unfavorable soil and 
germinating conditions at planting time. 
For the reason described above hand cut seed which usually contains none of the outer rind of the fruits is 
superior to machine harvested crops, especially muskmelon, certain of the squash, etc., which are more often 
harvested by hand methods under normal circumstances. 
We do recommend that seedmen’s supplies come from those production areas which have proven their free¬ 
dom of plant diseases. 
DISEASES OF CUCURBITS 
BACTERIAL WILT: 
Bacterial Wilt was first discovered near Washington about 1893. It affects Cucumber, Muskmelon, Squash 
and Pumpkin but Watermelons are almost wholly immune. The term wilt exactly expresses the symptons that 
may be observed on the outside of the plant. When infection takes place bacteria clog the water vessels of the 
stem and roots until the plant has wilted and died. 
Diagnosis may be determined by testing the sap for viscosity. The sap in a healthy plant is clear and watery 
but when bacterial wilt is present the fluid appears sticky when allowed to collect on a cut surface of the stem. 
In severe cases the sap may be milky white in color. 
CAUSE: 
The parasite is Bacillus tracheiphilus and depends on the common cucumber beetle for aid in its life cycle. 
The bacterium lives over the winter in the digestive tract of the beetle and thus is disseminated to the young plants 
through injuries and its spread is more general when moisture is prevalent. The organism is very sensitive to 
heat. Its thennal death point is 110 degrees F. 
CONTROL: 
While the plants are young control depends on the eradication of the striped and 12-spotted cucumber 
beetles. As the plants grow older a 4-4-50 Bordeaux spray or Copper Lime Dust aids in lessening the number 
of infections. The infected plants should be removed from the field. (See control formula for beetles under 
Plant Insects.) 
MOSAIC 
Mosaic, which is also known as “White Pickle” nubbin disease and Chlorosis has been known for many 
years. It is generally prevalent throughout the United States and Canada. Next to Bacterial Wilt it is probably 
ONE HUNDRED FORTY-THREE 
