Beginning in 1886 he worked in the laboratory of plant pathology at the Institut nationale agronomique, where he later served as a lecturer of descriptive botany (from 1895) and plant pathology (from 1898). In 1899 he was named director of the Station de Pathologie végétale in Paris.[1]
His name is associated with the mycological species Aspergillus delacroixii (synonym, Aspergillus nidulans var. echinulatus).[2]
Atlas de botanique descriptive comprenant l'étude des familles les plus importantes au point de vue économique (cryptogames et phanérogames) (1898) – Atlas of descriptive botany.
Les maladies et les ennemis des caféiers (1900) – Diseases and pests of coffee.[4]
Maladies des plantes cultivées; with André Maublanc (2 volumes, 1908–09) – Diseases of cultivated plants.
I, Maladies non parasitaires (non-parasitic diseases), by Delacroix.
II, Maladies parasitaires (parasitic diseases), by Delacroix and Maublanc.[5]