Beginner Gardening: Pruning flowering quince (I think that's what it is), 3 by RESORT2ME

RESORT2ME wrote:
Summier 2012 this 'brush' was overgrown and looked sick with mildew and worse. I've cut it back and moved the plants to separate them somewhat.
A week ago they were budding up and now are all frozen with overnight lows in 20s.
I see where a lot of old trunks and branches have moldy looking ends, maybe 5" long.
I want to lopper these and dispose of the sickness.
Is it wrong to cut while it is freezing?
The fruit was sick with mold (picture). I want to correct the situation.