V. BACTERIAL CANKER OF TOMATO 



Type. — This disease (Figs. 143 and 144), which for want 

 of a better name I first called The Grand Rapids disease, after 

 the locality in Michigan from which it was first sent to me and 

 where it occm-red seriously over large fields, is an infectious par- 

 enchymo-vascular wilt of the tomato (and probably also of the 

 potato), somewhat resembling the brown rot of Solanaceae due to 

 Bacterium solanacearum and often confused with it, but differ- 

 ing in a number of particulars, e.g., it is highly infectious through 

 the above-ground parts ; there is less brown stain in the bundles 

 and not so strong a tendency to develop incipient aerial roots 

 (Fig. 145) ; there is a slow shriveling of the leaflets one after 

 another (Fig. 146) rather than a sudden general wilt of the leaf; 

 the petioles are not reflexed; the meristem is attacked and cor- 

 roded into cavities, e.g., the heart of the incipient roots (Fig. 

 147); the phloem is specially susceptible to disorganization 

 (Figs. 148 to 150) ; and there is a strong tendency of the bacteria 

 to come to the surface through fissures on the shriveling leaves, 

 fruits and shoots (Figs. 151 to 154), thus affording an abundant 

 surface slime for the above-ground infection of neighboring 

 plants (through stomata) ; infection through broken roots has 

 also been observed (Fig. 155). The disease spreads easily from 

 one plant to another often by stomatal infection (Figs. 156 to 

 158) and is very destructive. It is, I believe, primarily a 

 phloem disease. I think also that it is a seed-borne infection. 

 I have seen its yellow slime close under the seeds in the middle 

 of green tomato fruits, both in the vascular bundles of the peri- 

 carp and in those of the placenta, and ^Iso once in the base of 

 an immature seed, but I have not yet actually traced it into or 

 plated it from the ripened seeds. Whether or not it actually 

 occurs in the interior of seeds capable of germination, the fre- 

 quent extensive invasion of the outer part of the tomato fruit 

 is certain to bring about a surface contamination of the seeds. 

 It occurs in the Northern United States both under glass and 



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