X marks the spot. As is usual a big X will get put down over the center of the city before the heavy spraying starts. In this case what appears to be clouds are actually the diffuse chemicals from previous round of sparying. Black dot at lower part may be a bird, or ufo, not sure.

With the sky covered with the diffuse "clouds" of the previous round, a new trail gets laid in. Turbulance from the plane gives it a scalloped look

Violet dot is most likely lens flare from the sun.

Although the sky is almost completely overcast with the previous spraying, they come back to fill in the little blue area left.

Violet dot is most likely lens flare from the sun.