When to Prune Butternut Suckers?

One of my young (1 year old) Butternut trees has a couple new saplings growing up from the ground beside it; I assume they are suckers. (See photo.)
(Are Walnut trees known for sending up suckers?)

I am wondering if I can cut these suckers off any time of the year, or should I wait until the Autumn, when Walnut trees are usually pruned?

What is best practice for dealing with these suckers?

Suckers can be pruned off at anytime.  They pull some of the growth away from other areas of the tree so I always break them off at first sight.

I like to flick suckers off with a finger while they are young and soft. Seems less damaging to the underlying wood, and is easier than getting in there with secateurs later in the year.