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Euxoa tronella are medium-sized moths (3.2-3.6 cm wingspan) with pale tan or buff forewings variably dusted with dark scales, with some specimens almost immaculate. The transverse lines are obsolete or marked with a few dark scales, and the reniform and in particular the orbicular spots are poorly defined, and are marked only by a patch of grey scales. The terminal area is usually darker grey, with a series of small dark crescents marking the terminal line. The fringe is the same color as the ground. The hindwings are white, with the outer half shaded with smoky brown in some specimens and occasionally with a discal bar and a faint median line. The fringe is white. The similar E. citricolor has pale yellow, not buff, forewings. Also similar to lightly marked specimens of E. catenula, which are white or grey, not buff, and which have prominent dark spots on the costa at the antemedian and postmedian line location. Euxoa tronella is a member of the detersa group of the subgenus Euxoa. Keys to the group, subgenus and species are available in Lafontaine 1981 and 1987.

From western North and South Dakota, west across southern Saskatchewan and southeastern Alberta to Washington, south to southern California and northern New Mexico. In Alberta it has been collected in the arid grasslands region, north to Tolman Bridge Recreation Area in the Red Deer River valley.