My Locust tree leaves are yellowing.
You don't mention if this is a young tree planting or a mature established tree.
Yellowing leaves can indicate a watering issue; too much or too little.
If the tree is new, water frequently enough so that the top few inches of soil are moist but not soggy. Crumbling soil is too dry, soggy soil is too wet.
If it is a mature tree make sure the soil is well draining.
Hardwood mulch can help with moisture retention if the soil is drying to quickly.
You should always inspect the tree for any infestation to rule out that issue.
If the watering issues are resolved, but leaves continue to yellow, you may want to have a soil test performed, as this could be a nutritional deficiency.
https://www.gardeningknowhow.com/ornamental/trees/locust/locust-tree-information.htm
My locust tree is losing its leaves in site of treatment with Bayer tree and shrub food /insecticide. Leaves start dropping in early May.
What insect are you spraying for - the honeylocust spider mite? Heavy infestations of spider mites cause early leaf drop, so it may not necessarily be the insecticide, but the insect you are spraying for.
For more information on locust trees, please visit the following link:
https://www.gardeningknowhow.com/ornamental/trees/locust/locust-tree-information.htm
Beginning of summer in central California, the tree is about 10 years old and is now dropping its leaves.
As the weather has warmed and the moisture decreases, increased water loss from the tree will cause them to drop excess leaves. This is their natural strategy to conserve energy.
If a spring is wetter then normal, this can make the issue even more noticeable.
If you provide watering and you see no other signs of disease or pests, there is no concern.
I have a 1" sucker growing from the crown of a black locust. What effect will removing this do to the hardiness of the tree?
Removing suckers and watersprouts (suckers that grow from the trunk, branches or crown) is good for trees and keep them growing strongly. They should be removed right away by cutting them off close to the trunk.
Will it kill a locust tree if you cut the top out of them
Tree topping is never a good idea.
This article has more information.
https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-topping-information.htm
Wait until late winter to prune your honeylocust tree. These trees are prone to stem cankers, or lesions, that can cause extensive limb dieback.
https://www.gardeningknowhow.com/ornamental/trees/locust/locust-tree-information.htm
How many years before black locust begins to bloom?
Because these trees are so fast growing you should began to see flowers within a few years of planting.
https://www.gardeningknowhow.com/ornamental/trees/locust/growing-black-locust-trees.htm
Can you grow a new Black Locus tree from cutting of old tree County crew cut down my Black Locus tree and I am quite upset about it - only had two on our while 5 acres. I want to know if I get cutting off the tree they knocked down could I grow new tree?
It would not hurt to try to root a few of the branches. This article will help
https://www.gardeningknowhow.com/ornamental/trees/tgen/planting-trees-from-twigs.htm