Butler, Sir Edwin John (1874–1943), plant pathologist, was born 13 August 1874 at Kilkee, Co. Clare, the second son of Thomas Butler (d. 1919) and his wife, Annie (d. 1898), the daughter of James Barry of Co. Limerick. Thomas Butler's brother was Sir William Francis Butler (qv); they were of a gentry family from Ballycarron and Suirville, Co. Tipperary. Thomas Butler had lost property at Ballyslateen, Co. Tipperary, in a dispute, and was obliged to take a position as a resident magistrate in Kilkee and later in Mallow, Co. Cork. There were three sons and three daughters in the family; the eldest son was the historian William Francis T. Butler (qv). Edwin was sent to school at Gainsborough in Lincolnshire but, when he became seriously ill in 1887, he returned to Ireland to be tutored at home. In 1890 he attended the Christian Brothers’ school at Cork, where he gained a scholarship in mathematics, and went on to Queen's College, Cork, to study medicine. He had little interest in the subject, though he graduated from the RUI with the degrees of MB, B.Ch. and BAO in 1898.
Thereafter Butler concentrated his attention on botany and cryptogamy. He was awarded an 1851 exhibition scholarship for two years’ travel to study botany at Paris, Antibes, Freiburg and the Royal Botanic Gardens at Kew. In 1900 he was appointed to the newly created post of cryptogamic botanist to the government of India, and went to work in Calcutta. At the Seebpur botanic gardens he developed an interest in pathology in tropical plants, working particularly on Indian wheat rusts. Organisms such as these, and their interactions with their hosts, had until then been investigated, but Butler's research shed new light on many economically important aspects of botany and mycology. In 1905 he was transferred to Pusa as imperial mycologist. The following year he co-authored a monograph on Indian wheat rusts with J. M. Hayman, as well as writing his own account of sugar cane diseases of Bombay. In 1907 his authoritative account of the genus Pythium, a water mould, appeared. Other topics he investigated included Phytophthora infestans and Fusarium wilt diseases, and in 1913 he worked on the diseases of rice. His Fungi and disease in plants appeared in 1918, and he and colleagues in India and elsewhere worked on a definitive list of Indian fungi. The fungi of India (1931) was a joint publication with Guy Bisby, and was the standard text for many years, reprinted in 1999. In 1919 he was appointed joint director of the agricultural research station at Pusa, and in 1920 agricultural adviser to the government of India.
In 1920 Butler left India to take up his appointment as founder director of an organisation which developed into the Imperial Mycology Institute, latterly known as the International Mycology Institute, at Kew. His primary aims at the institute were the accumulation and distribution of information on plant pathology as well as the formation of a reference library. He established an organisation to identify fungi, as well as the Review of Applied Mycology (begun in 1922, and later known as the Review of Plant Pathology). From July to August 1921 he visited the USA to garner support for the institute. He was appointed companion of the Order of the Indian Empire in 1921. Despite an increasingly heavy administrative workload, he was able to present three papers at the Pan-Pacific Science Congress held in Australia in 1923. On the same trip he toured Canada, Hawaii, Fiji, and New Zealand and met many commonwealth pathologists. He was elected fellow of the Royal Society and president of the British Mycological Society in 1926. In 1927 he visited Nyasaland to examine fungal diseases there. He was president of the Association of Economic Biologists in 1928–9. In 1931 he visited Sudan to study diseases of cotton cultivation and in 1932 he was created CMG. In 1934 he was elected to the council of the Royal Society and in 1935 he resigned his directorship of the institute. He was a member of many committees concerned with advice and research on pathology. From October 1935 to January 1941 he worked as paid secretary to the Council for Agricultural Research, where he planned the field station at Compton Manor in Berkshire. In 1938 he received an honorary LLD from the University of Aberdeen, and in 1939 he was knighted. In 1941 he retired for reasons of health, but worked on to complete his part of an important textbook, Plant Pathology, in which he collaborated with S. G. Jones. It was published six years after his death, which occurred in a nursing home in Weybridge, Surrey, on 4 April 1943. On 16 February 1901 he had married Nina, daughter of Alfred Le Mesurier of Guernsey; they had a son and two daughters.