This looks very much like striped cucumber beetle damage. Once the beetles get established it is very hard to control them; the adults can move very quickly and can mash up a leaf by poking holes in it in very short time. Then they move on to another leaf. On the upper and lower surfaces of leaves and in flowers is where to find them active. One way to handle the beetles is to grow young plants from seed in a protected environment to get them growing fast and without checks due to cold weather or lack of rain and plant out when they are vigorous into warm soil and watch over them carefully.