Horsfall 



The Fight with the Fungi 



shown that the disease conlcl be trans- 

 ferred from plant to plant but no 

 "causal organism" could be found. It 

 was suspected then that the "causal 

 organism" was ultra-microscopic and it 

 was labeled by the old term, virus, 

 which originally meant poison. But 

 virus has now come to mean a cause 

 for disease that cannot be seen with a 

 microscope. In the middle of the 

 1930's, the Radio Corporation of 

 America invented a new kind of micro- 

 scope depending upon a beam of elec- 

 trons, not light. With this machine, 

 viruses can now be seen; we know 

 about how big thev are, and can make 

 out something of their characteristics 

 and structure. 



CHEMICAL WARFARE 



Once the role of fungi in causing 

 disease was established, control meas- 

 ures became feasible. Much of the 

 modern control of plant disease is ac- 

 complished with fungicides that search 

 out the fungus and kill it. 



In the last 10 years, more has been 

 learned about chemical control of fungi 

 than in the whole course of history be- 

 fore. Chemical killers of fungi are 

 called fungicides. These are the sub- 

 stances that will help to keep the roof 

 from falling in. Tliey 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 



131 



Cheever had read some of the agri- 

 cultural literature and remembered that 

 a Frenchman, Prcvost, had killed the 

 fungus of wheat smut with copper sul- 

 fate and thus had been able to control 

 the disease. Prevost worked in 1807, al- 

 most 40 \ears 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 con- 

 trol of the wheat smutj 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 ex- 

 perimentally, but I suspect that he did 

 tr)' 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 tech- 

 nical 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 to- 

 gether 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 foilage where it 

 would have solved the Irish famine. 



In 1882, almost 40 years after the 

 Irish famine, Morren's mixture, minus 

 the salt, was rediscovered in the prov- 

 ince of Bordeaux in France by Profes- 

 sor Millardet. Tlius was born Bordeaux 

 mixture, the most famous fungicide of 



