The festival of the Robigalia is celebrated to appease the God Robigus (or perhaps the Goddess Robigo; the gender of this deity, who originated as one of the numinae, is uncertain), who is the deity of wheat-rust, mildew, and blight.
It is an ancient festival of the agricultural calendar, and is celebrated by the Flamen Quirinalis. Both a red dog and sheep are sacrificed to Robigus, along with wine and incense; prayers are then spoken to protect the crops. There is some connection with the ascension of the star Sirius, but it is unclear.
Verminus, a God who protects cattle against worm disease, might also be honored on this day.
Source: Nova Roma