This past 
week we celebrated the Irish holiday, St. Patrick’s Day. Never mind that St. Patrick was English and that the English and Irish had been enemies for centuries. Here too in the United States, St. Patrick’s Day is celebrated widely, mainly because of the migration of millions of Irish to the States during the 1840’s. In fact, in a short time, the population of Ireland was halved from the result of immigration and death of its citizens from starvation.
A form of the disease called Phytophthora destroyed the main staple of the Irish, which was potatoes as they grew well in the cool Irish climate. An unusually cool rainy weather period started the disease’s spread which caused a rotting of the plants.
Many forms of Phytophthora exist and are a problem in farm crops, forests and ornamental plants but do very little harm unless conditions are ripe for their spread as they were in Ireland in the 1840’s. Some forms of the disease require soil temperatures of 55 degrees or more and actually are able to survive to attack the roots of their host plant when soils are waterlogged for at least 24 hours as the organisms have a flagella, enabling them to swim toward their host to start an infection.
Other forms of the pathogen are airborne and will impact tender foliage of plants once they land on their host. How strange that such a small organism as Phytophthora could cause Ireland so much death and destruction and cause millions to cross a vast ocean to the United States of America.
There are other dangerous organisms such as Ralstonia that are watched closely by the USDA as the disease kills a variety of important crops. Almost ten years ago, Geraniums propagated in Kenya were found to be infected and were promptly destroyed with other greenhouse crops in order to stamp out the threat to agriculture. To be sure the role of the federal government is broad with the USDA serving not only as a regulator in a variety of sectors in agriculture but its role is a watch dog of threats to agriculture from the spread of diseases, invasive weeds and insects threatening our food supply. While the general belief is that our food supply is well secured, it is not impossible that such a disease in the form of the Irish potato blight could occur.
In the economic sector, the 1920’s roared on with President Hoover promising “a chicken in every pot”. Then came 1929.