Does anyone know what’s being sprayed from a white truck driving through neighborhoods at night in Spring?

I might sound crazy as all hell, but I’m in Spring and I come home pretty late sometimes around 10-11p. A few times I’ve seen a noisy white truck drive down my street with something being sprayed into the air from the back. It only happens late at night. The first time I saw this I was freaked out because it was late and looked weird. Please don’t tell me I’m the only one who’s seen this lol. Does anyone know what this is about?