Holes in the leaves of hedging plants can be quite common but are not a serious concern. They are often due to leaf scorch rather than disease and the damaged leaves will fall off as new foliage appears in the spring.
An easy way to help prevent leaf scorch is by watering in the morning or evening when the sun is not strong. Any water remaining on the leaves may be evaporated by strong sun, which can burn through the leaves causing holes. This is not detrimental to the overall health of the plant in any way but is best avoided where possible. During periods of sun showers, when a combination of moisture on the leaves and sunshine are inevitable, leaf scorch is unfortunately unavoidable but your plants will soon recover.