Hello, 

Thanks for reaching out! Here is a helpful UMN Extension article about pruning trees: https://extension.umn.edu/planting-and-growing-guides/pruning-trees-and-shrubs

Crabapple trees are best pruned in late winter. This decreases the chance for disease and infection to spread. 

As for the ash tree, it is also recommended to wait. The Emerald Ash Borer is highly active right now, and the removal of ash trees, branches, or stumps should be avoided. Here is more information: https://extension.umn.edu/tree-and-shrub-insects/emerald-ash-borer

Good luck!