robigalia

One of a number of Roman celebrated during this time of year to ensure a good growing season and bountiful harvest, the feast of the for the god Robigus was held on this day in the agricultural outskirts of the city.
The god, which was designated as the divine representation of fungal blight or rust needed to be propitiated in order to ensure that the crops wouldn’t spoil in the fields. Understood as a separate, corrupt manifestation of the same infestation that could be harnessed for fermentation, the games held at this time with their attendant feasts (see also) were also marked by rather dark sacrifices that expressed their anxieties over crop failure—especially for one this late in the growing seasons that wouldn’t be easy to recover from. Whereas animal sacrifice generally was reserved for livestock that was part of the Roman diet and was shared in a communal meal, Robigalia rather gruesomely demanded a dog with a red coat—that matched the rust disease—as form of homeopathic magic.
Other observations included a celebration of—for whatever reason—of male sex-workers, professional female prostitution having had their own honours in the previous days, specifically on Vinalia urbana, the grape harvest on 23 April. Though without the cruel bits, thankfully—or the fun bits either, I suppose, the holiday is preserved in Western Christianity with the same day of prayer and fasting known as Rogation (from the Latin to beseech—to ask God for protection from calamity) and was done to cleanse the body and mind in anticipation of the Ascension and farmers often had priests bless their crops, often holding mass and processionals in the fields.