High Temperature Damage

This is not likely an infectious disease, but looks like typical high temperature damage, maybe in combination with a lack of water. Even if all the other plants in the hedge row look fine, it sometimes happens that one plant does not develop as healthy a root system as the other plants, or the soil in the immediate area around the roots of the affected plant is not holding sufficient amounts of water, even though we’d assume that the soil is the same as for the other plants; sometimes its just different enough to make the one plant grow differently, or suffer damage. We recommend using a soil probe (which can be made at home or purchased from a garden center) to check the moisture of the soil around the root zone, and water when necessary to keep the soil evenly moist.