56 HORSFALL 



caused it because nobody could yet see it. The year 1726 marks a significant 

 step forward in our understanding of causation of disease. And this was 

 recorded in a law book. 



DISEASE CHANGES THE LAW 



The colony of Connecticut in 1726 passed a law specifying that barberries 

 must be eradicated in the vicinity of wheat fields, and the General Court 

 (legislature) set a fine of 20 shillings for failure to kill out the barberries and 

 a further fine of 10 shillings per month until the barberries were eradicated. 

 The law says, "Whereas the abounding of barberries is thought to be very 

 hurtful, it being by plentiful experience found that, where they are in large 

 quantities, they do occasion or at least increase the blast on all sorts of Eng- 

 lish grain." Looking back on the situation from the vantage point of 1956, it 

 is an amazing thing that the Legislature of Connecticut would pass a law 

 eradicating the barberry plant in order to control a disease on another plant. 

 This must have sounded fantastic to the lawyers of that day. In fact, you 

 can hear a little bit of skepticism in the statement, "Whereas the abounding 

 of barberries is thought to be very hurtful." The effect of the barberries on the 

 wheat was scoffed at by the botanists of the day, but the practical wheat 

 grower was very insistent that the barberries produced the blast. It was not 

 until ISO years later that the great German plant pathologist De Bary dis- 

 covered that the wheat rust fungus spends part of its life on the barberry 

 plant. Without the barberry plant to support it during part of the year, the 

 wheat rust would have died in Colonial Connecticut. This indicates the re- 

 markable perspicacity and keen observation of the practical wheat grower of 

 long ago. They said in effect, "Barberries cause wheat rust." Barberries they 

 could see. 



In passing we might note that the Connecticut law led eventually to bar- 

 berry-eradication laws in most of the wheat-growing areas of the world. 

 Actually barberry eradication has not worked well in America as a method 

 of controlling wheat rust. The fungus winters in Mexico, and the microscopic 

 spores ride north on the spring storms. Hence, the fungus does not now need 

 the barberry to get it through the year. Nevertheless, the barberry law initially 

 promulgated here in Connecticut in 1726 might in some ways be considered 

 as altering the course of history. As far as I know, it was the grandfather of 

 all laws specifying that it is the duty of the State to protect people from the 

 consequences of pestilence. It was the first quarantine law. 



Jethro Tull, the famous English writer on agricultural subjects, in his well- 

 known book Horse-hoeing Husbandry, published in 1733, decided that insects 

 were the cause of wheat rust because he thought that the spots on the leaves 

 were caused by excreta from insects. He could see the insects and was in- 

 clined to ascribe the disease to this visible cause. 



