Complex sentence: He was also a pioneer in the study of phytopathology, dealing with plant diseases, as well as supervising and conducting reasearch on economic botany and serving on committees charged with advancing scientific learning in Ireland.
Split into simpler sentences: He was also a pioneer in the study of phytopathology, the scientific study of plant diseases. He supervised and conducted reasearch on economic botany and served on committees charged with advancing scientific learning in Ireland.