The black walnut tree is grown not only for hardwood to be made into lumber, but also to provide shade and edible walnuts. The tree has few competitors because the roots produce a toxin known as juglone in the roots of the plant as well as the buds and nut husks. Because the shells of black walnuts are thick and hard and the husks are filled with juglone, some walnut tree growers prefer to block the fruit of walnut trees.
Select a chemical growth inhibitor containing ethephon.
Time the application of the chemical for a point just before the walnuts set on the tree.
Put on protective clothing including breathing protection, eyewear, long pants, long sleeves and gloves.
Mix the chemical at a ratio of 1 tsp. per 6 oz. of water.
Pour the chemical mix into the holding chamber of a pressurized spray applicator.
Prime the pressure of the applicator by grasping the pump handle and moving it up and down until you have built up sufficient pressure in the applicator.
Carry the applicator wand with one hand and the holding tank with the other. Turn on the wand by squeezing the trigger to emit a fine spray mist from the tip.
Pass the wand over the walnut tree using slow, even strokes.
Shower immediately after using the chemical so you do not absorb it into your body through skin contact.