One of the world¡¯s leading experts on pesticides?and their effects on insects and mammals, including humans, has been remembered as ¡°an incredible mentor¡±.

John Casida was born in Phoenix, Arizona, on 22 December 1929. His father, Lester, was initially a teacher in the local one-room school but, after securing a PhD, became a professor of animal science at the University of Wisconsin-Madison. The younger Professor Casida followed him into the same institution, gaining a bachelor¡¯s degree in entomology (1951), then a master¡¯s in biochemistry (1952) and a PhD in entomology, biochemistry and plant physiology (1954), although his progress was interrupted by service as a medical entomologist with the US Air Force during the Korean War (1953).

Once qualified, Professor Casida joined the department of entomology at Wisconsin-Madison, where he directed the Pesticide Chemistry and Toxicology Laboratory, and was promoted to full professor in 1961. Three years later, he moved on to the University of California, Berkeley, where he eventually became the William Muriece Hoskins chair in chemical and molecular entomology (1996 to 2011). Although he gave up teaching in 2014, he remained active as a researcher and a mentor to the next generation.

A keen insect collector in his youth, Professor Casida devoted much of his research efforts to elucidating how DDT and other synthetic pesticides affected insects, how they are metabolised by mammals, including humans, and their impact on the environment. Through the insights they gained, he and his colleagues were also able to develop new compounds?that were equally effective but far less damaging.

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The co-author of more than 850 publications and co-holder of 31 patents, Professor Casida had a passionate enthusiasm for his research?that could lead to absent-mindedness (he forgot to collect his future mother-in-law, as agreed, on the way to his wedding). He was exceptionally wide-ranging in his interests and always willing to pursue promising but unexpected leads. ¡°You follow the problem,¡± ¡°and it¡¯s the people in the lab that make that happen. If something is totally unexplainable and totally unanticipated, if it approaches the absurd, this may be the best reason for dropping everything else and focusing on that.¡±

Sarjeet Gill, a former student of Professor Casida¡¯s who is now distinguished professor of molecular, cell and systems biology at the University of California, Riverside, described him as ¡°an incredible mentor¡± and ¡°the most pre-eminent pesticide toxicologist in the last two centuries. John changed the way we investigated mechanisms of toxicity at all levels¡±.

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Professor Casida died of a heart attack on 30 June and is survived by his wife, the artist Kati Casida, two sons and two grandchildren.

matthew.reisz@timeshighereducation.com