For a while my daughter was interested in possibly working in agrochemical or food manufacturing. Her intended path for that was through chemical engineering with a specialized concentration later. She has since changed her mind but we did look at a lot of schools that had agricultural engineering programs and the like. I would suggest to your friend to reach out to some of the universities and talk through the questions. Our experience was that departments and profs were very open to talking through questions like this. Cornell, OSU, Purdue, U of WI, UC Davis, all have solid programs. Also a quick google search yielded this: https://study.com/articles/Plant_Pathology_Career_Options_and_Education_Requirements.html