146 BACTERIA IN RELATION TO PLANT DISEASES. 



compelled to practice field hygiene. In bringing this about seedsmen generally (middle- 

 men) should cooperate with State authorities. Second, the origination of resistant varieties 

 by cross-breeding and selection. By this method alone, wisely pursued, it ought to be 

 possible to overcome the disease, but not immediately. Third, treatment of the seed-corn 

 with germicides, such as mercuric chloride, formalin, etc. Fourth, bactericidal powders 

 or sprays applied during the seedling stage when the water-pores are functioning and the 

 plants are specially liable to contract the disease. Probably the plants will prove very 

 sensitive to chemicals during this stage of growth, and one should therefore proceed with 

 caution lest the damage wrought be greater than that likely to result from the disease. 

 The first and third methods are the more feasible. These directions are intended primarily 

 as suggestions to plant pathologists rather than as advice to growers, although some of the 

 latter might be able to work out their own methods of treatment. 



To prevent the introduction of the disease into new fields, growers of sweet corn for 

 seed, and seed-firms generally, should cooperate with the farmer. The former ought not 

 to put on the market seed-corn likely to transmit the disease, that is, corn grown on land 

 subject to this disease, and the farmer as a matter of ordinary precaution ought to treat 

 his seed-corn with some germicide before planting it, unless he knows beyond doubt that 

 it was derived from healthy plants. The thermal death-point of the organism is so high 

 (53 C.) that probably hot-water treatment of the seed would not be effective. Soaking 

 the seed 20 minutes in i to 1,000 water-solution of corrosive sublimate in glass vessels or 

 in wooden pails or tubs is the method most likely to destroy the organism on the surface of 

 the kernels without serious injury to the latter. It will slightly retard the germination of a 

 portion of the kernels, but should not destroy any of them, if the treated seed is immediately 

 rinsed in clean water on taking it out of the germicide, or dried at once and planted without 

 rinsing. The writer, as the result of experiments made in 1909 (see vol. II, p. 196), has no 

 hesitation in advising exposure of suspected seed to mercuric chloride water (i : 1,000) for 20 

 minutes just prior to planting. This will destroy most of the bacteria on the seeds and will 

 not prevent germination or seriously delay it. The dry seed-corn should first be wet with 

 alcohol, then covered with the germicide, removed at end of 20 minutes, rinsed slightly, and 

 planted at once, or else dried quickly. The corn must not be soaked in advance of treatment ; 

 nor must the rinsing be prolonged. Such treatments, of course, will not reach the organism 

 when it is lodged in the interior of the kernel. As an added precaution, therefore, all 

 shrunken, suspicious kernels should be removed from the seed-corn before it is treated. This 

 may be done by running the kernels through a fanning mill and by a little subsequent hand- 

 picking. The latter should not be neglected. 



To recapitulate: The greatest pains should be taken to secure only sound seed-corn, but in 

 the present indifferent state of the seed-trade even the best should be treated with mercuric chloride 

 before planting. On fields subject to the disease only resistant varieties should be planted. 

 Manure containing corn stalks from diseased fields, or gathered from animals pastured in such 

 fields, shotdd never be used on land designed for corn. 



PECUNIARY LOSSES. 



Nothing very definite can be expressed under this head. There are no general statis- 

 tics available, only individual instances. 



The disease is a bad one on Long Island, and, if the writer's inferences under "Etiology" 

 are correct, also in at least one locality in Ohio. That the disease may take from 10 to 70 

 per cent or more of the plants in experimental plots, not artificially inoculated, is also shown 

 by the record of the trial plots mentioned on pages 117 to 1 20. 



The general experience on Long Island is summarized by Stewart as follows : 



Occasionally, an entire crop has been ruined and losses of from 20 to 40 per cent have been fre- 

 quent; but in the majority of cases the loss has been so slight as to pass unnoticed by the farmer, 

 although one familiar with the disease could readily detect it in almost any field of early sweet corn 

 on Long Island_during'the past season. 



