These are some interesting tidbits that could cause your characters a bit of frustration and hardship should their cabbage develop this black rot.
SYNOPSIS OF RULES FOR PREVENTION.
The field observations described above, taken in connection with the characters of the disease as previously worked out, lead the writer to believe that this trouble may be successfully combated by means of what he has frequently designated as field hygiene. If he were asked to give in concise terms a few rules for avoiding this disease they would be about as follows:
1. Plant the cabbage seed on land where this disease has never appeared. When the plants are ready to set out inspect the seed bed very carefully, and if any cases of the disease are found reject all the plants and set from some other bed. One can not afford to run any risk of infecting his land by the use of seedlings from suspicious beds. It would be better to plant some other crop than to take this risk. A good practice is to strew the land to be used for seed bed with straw or dry brush and burn it over before plowing. The seed bed should be made in a different place each year.
2. Set the plants on land which has not been in cabbages or other cruciferous plants for some time. If it is impossible to avoid following cabbages by cabbages, at least take the precaution to plant only on land which has never suffered from this disease. To follow any other course is simply to invite the trouble. The practice of planting cabbages after cabbages for a long series of years also invites other parasites, and must as a rule be considered very bad economy.
3. As a matter of precaution avoid the use of stable manures, since these may possibly serve as a means of carrying the disease into uninfected fields, that is, through cabbage refuse fed to animals or thrown into the barnyard or onto manure piles. As far as possible make use of commercial fertilizers in place of barnyard manures, both in the seed bed and in the field, at least until it shall have been shown conclusively that there is no danger in the manure pile. Too much stress can not be laid on the necessity of keeping the germs out of the soil, and consequently on the avoidance of practices which, if not absolutely proved to be dangerous, are at least questionable.
4. Do not turn animals into diseased fields and then allow them to wander over other parts of the farm. Cattle or other stock should not be allowed to roam in cabbage fields where this disease prevails.
5. All farm tools used on infected land should be scoured bright before using on uninfected land. The transfer of soil from infected to healthy fields ought in all cases to be reduced to a minimum.
6. Keep up a constant warfare against insect enemies, especially the cabbage butterfly and the harlequin bug.
7. As a palliative remove badly affected plants from the field as fast as they appear. In early stages of the disease—i. e., while it is still confined to the margins of the leaves and has not yet entered the head or stump—go over the fields systematically about once every ten days and break off and remove all the affected leaves. Do not throw this refuse into cultivated fields, or into ditches from which it can be washed to other fields, or on roadways to be tracked about. It should be burned or put into a deep pit in some fence corner or other out-of-theway place.
8. Weeds which harbor the disease, especially the wild mustards, must be destroyed systematically.
9. Store cabbages from diseased fields only when it is impossible to sell them in the fall, and in such cases take particular care to reject all heads showing any trace of black in the stump and to keep all parts of the houses below 40° F. If any affected heads are stored tliey should be put by themselves in the lowest, coolest part of the house.
Source: The Black Rot of Cabbage ©1898