Disclosed are solid forms of 1-[4-[4-[5-(2,6-difluorophenyl)-4,5-dihydro-3-isoxazoyl]-2 -thiazolyl]-1-piperidinyl]-2-[5-methyl-3-(trifuoromethyl)-1H-pyrazol-1-yl]ethanone (Compound 1). Also disclosed are methods for the preparation of solid forms of Compound 1 and for the conversion of one solid form of Compound 1 into another form. Further disclosed are methods for controlling plant diseases caused by fungal plant pathogens comprising applying to a plant or portion thereof, or to a plant seed, a fungicidally effective amount of a solid form of Compound 1. Additionally disclosed are fungicidal compositions comprising a fungicidally effective amount of a solid form of Compound 1 and at least one additional component selected from the group consisting of surfactants, solid diluents and liquid carriers and also compositions comprising a mixture of a solid form of Compound 1 and at least one other fungicide or insecticide.
