James Gordon Horsfall (January 9, 1905 – March 22, 1995)[1] was an American biologist, plant pathologist, and agriculturist.

He worked briefly with Dwight Isely, counting insects to determine the timing of insecticide application in cotton.

After graduating with a Bachelor of Science degree in 1925, he studied plant pathology at Cornell University, from which he received his doctorate in 1929.

[1][3] Horsfall was most noted for the discovery of several organic fungicides which changed the way crops' fungus diseases are treated worldwide.

[2] Prior to his discovery these diseases were treated either with heavy metals which were poisonous to humans or somewhat ineffective sulfur-based compounds.

[7] Horsfall later discovered that sugar concentrations in plant parts was correlated with resistance to fungal infection by Alternaria in potatoes.