Some Bacterial Diseases oe Plants. 17 
the wind is blowing over a sick field carrying with it fragments of 
rotting plants and infected soil. These germs are in the beads of 
moisture, referred to above, and finding a comfortable lodging place 
and abundant food and water supply, they multiply very rapidly, 
and being able to move about, soon find their way down through 
the water pores into the veins of the plant. Here they continue to 
multiply and work toward the stalk, leaving behind them the black¬ 
ened veins and withered blades. The germs may also gain entrance 
by means of the bites of gnawing insects and again by way of the 
broken roots at the time of transplanting. 
There is no question but that in many cases the plants are 
taken from the seed bed in a diseased condition and when trans¬ 
planted into the field spread the germs through the soil, rendering 
it unfit for cabbage growing in the future. When the source of the 
infection is confined to such a limtied space as the seed bed, it is 
possible to sterilize the soil to a depth of five or six inches by cover¬ 
ing it with brush and cord wood and burning it, the heat produced 
penetrating sufficiently deep to kill most of the surface bacteria, as 
well as troublesome weed seeds. This is a very common practice 
with tobacco growers and has met with great success wherever em¬ 
ployed. If this is not practicable, the seed bed should be located in 
a new place each year and where cabbage has never been grown. It 
is only reasonable to suppose if plants are in a good, vigorous con¬ 
dition when transplanted into a “healthful” field, their chance of 
living is vastly greater than if sick from the start. 
When stable manure is used for fertilizer, every precaution 
should be taken to keep infected cabbage refuse from getting into 
the manure, for in this way the whole heap will become infected 
with the rot germs and when it is spread on the field the entire plat 
will become inoculated. One of the worst plant disease epidemics 
on record was caused in this very way. The writer refers to the 
present watermelon wilt in North Carolina, South Carolina, and 
Georgia, where melon growing for the past six years has been 
practically abandoned by the smaller producers because of the rav¬ 
ages of the wilt. The only safe way to dispose of refuse is to 
burn it. 
It has been demonstrated experimentally by Harding,* Stew¬ 
art, and Prucha that the cabbage seed itself is contaminated with the 
black rot germs and that some of them could live over winter on 
the seed and become the source of infection to the young cabbage 
plants. They advise disinfecting the seed before sowing by soaking 
it in a 1-1000 solution of corrosive sublimatef for fifteen minutes, 
♦Bull. 251, N. Y. Expt. Sta. 
fCorrosive sublimate. See preparation of mercuric chloride described 
under Pear Blight. 
