Aphids – Present in Winter
Q: Do you know what these small, clear, yellow insects are called? They are in planters we have outside.
A: I’m writing this in Jan. 2017 during a warm week following temperatures in the teens. Despite the cold, these are green peach aphids.
I’ve read that adults can survive 40 degree weather.
Typically they overwinter as eggs attached to flowering cherry twigs. Perhaps your planters are in a protected spot outdoors which didn’t get very cold. You could attempt to control them with spinosad (click for sources) and emphasizing thorough coverage.
A systemic insecticide that contains imidacloprid (click for sources) could work but control is slow in cold weather.