This section is from the book "The Standard Cyclopedia Of Horticulture Vol2", by L. H. Bailey. See also: Western Garden Book: More than 8,000 Plants - The Right Plants for Your Climate - Tips from Western Garden Experts.
A soil parasite affecting cabbage and other cruciferous plants. It thrives best in acid soils and in some cases can be checked by a liberal use of lime, but its presence in any field in destructive abundance is seldom suspected until too late to save the crop. Planting cabbage or other cruciferous crops on such a field should not be repeated for several years, during which it should have continued dressings of lime and ashes. Care should be taken to secure uncontaminated soil for seed-beds, and to destroy all affected plants before cattle have access to them, as the disease may be carried by such refuse in the manure from cattle who have eaten it.
Infectious diseases which sometimes become so abundant in certain sections as to prevent the profitable culture of cabbage. They are all distributed by means of contaminated seed, by manure from cattle fed on diseased refuse, by soil carried on tools from affected fields; distribution in this way should be carefully avoided. All diseased plants should be destroyed by fire as soon as noticed. The soil used in the seed-beds should be sterilized by live steam or soaked in a weak solution of formaldehyde (one part to 260 of water). The seed should be soaked fifteen minutes in the weak solution of formaldehyde, then rinsed in clear water and immediately planted.
The securing of vigorous plants is sometimes prevented by the attacks of innumerable flea beetles, Phyllotreta vit-tata. This may be prevented by surrounding the beds with frames made of 10- to 12-inch boards connected across the top with 2-inch strips and then covered with 20- to 40-thread to the inch cheesecloth. This should be put on as soon as the seed is planted and be removed, in order to harden the plants, four to six days before they go to the field.
These are best guarded against by keeping the field perfectly clear of all vegetation for six to ten days before setting, then mix four quarts of bran meal or flour, one cup of molasses or sugar, and two tablespoonfuls of paris green, with water enough to make about the consistency of milk, and sprinkle on twenty to fifty times its bulk of fresh-cut grass and scatter over the field the night before setting the plants.
Keep careful watch of the plants and if the green worms appear in abundance and seem to reach full size, sprinkle or spray the plants with kerosene and whale-oil soap emulsion, or paris green and water in the proportion of four gallons of emulsion and one pound of paris green to fifty gallons of water. After the heads are two-thirds grown, powdered hellebore, one ounce to two gallons of water, should be substituted for the poisonous paris green mixture.
Although seldom very destructive north of Philadelphia, this is often the unsuspected cause of failure in the South, particularly of fall crops in light lands. The only practical remedy is the avoidance of affected fields or sterilizing the soil by freezing or live steam.