THE FIGHT WITH THE FUNGI 59 



trons, not light. With this machine, viruses can now be seen; we know about 

 how big they are and can make out something of their characteristics and 

 structure. 



CHEMICAL WARFARE 



Once the role of fungi in causing disease was established, control measures 

 became feasible. Much of the modern control of plant disease is accomplished 

 with fungicides that search out the fungus and kill it. 



In the last ten years, more has been learned about chemical control of 

 fungi than in the whole course of history before. Chemical killers of fungi 

 are called fungicides. These are the substances that will help to keep the 

 roof from falling in. They are the substances that will help in the fight with 

 the fungi. They comprise nowadays a vast armamentarium to assure farmers 

 of the means to protect food from fungi so that people may have it to eat. 



These compounds also were the end of a long and toilsome road. 



We have mentioned Dr. Lindley and his misconception of the role of the 

 fungus in producing the rot of the Irish potato in the famine year 1844. In 

 the very same year, an amateur plant pathologist. Judge Cheever of the Court 

 in New York City, came mighty close to providing the Irish with an answer 

 to their blight problem. Judge Cheever had read some of the agricultural 

 literature and remembered that a Frenchman, Prevost, had killed the fungus 

 of wheat smut with copper sulfate and thus had been able to control the 

 disease. Prevost worked in 1807, almost forty years ahead of the Irish famine. 

 The control of wheat smut by treating the seed with copper sulfate to kill the 

 fungus had become almost standard practice by the time of the famine in 

 1844. 



Judge Cheever, knowing this control of the wheat smut, had suggested that 

 copper sulfate be applied to the potato plant for the control of blight. As far 

 as I can find, there is no record that Judge Cheever ever tried this experi- 

 mentally, but I suspect that he did try it and it failed, because the copper 

 sulfate burned up his plants just as badly as the blight and was, therefore, 

 not practical. Copper sulfate does not burn wheat seed for numerous technical 

 reasons, but it does burn foliage and therefore could have been of no use in 

 the control of potato blight. 



The same year a Belgian amateur named Morren actually did put together 

 a safe mixture of copper sulfate. He mixed copper sulfate with lime and 

 table salt and applied it for the control of potato blight. The only trouble 

 with Morren 's method was that he poured the mixture on the ground where 

 the fungus was not and he did not pour it on the foliage where it was. Morren 

 missed the significance of the fungus on the leaf. He thought that the disease 

 came from a miasma arising from wet soil. Hence, he poured his mixture on 

 the ground, where it was worthless, rather than on the foliage, where it would 

 have solved the Irish famine. 



