Damage to Iris leaves in the pond
1. If Iris leaves are being eaten and look shredded like the blade of a saw - back to the central midrib, then you have an attack of Iris sawfly.
2. It is the caterpillar that does the damage in mid summer and this is grey & about 1" long.
3. It will eventually drop down to the soil and pupate to emerge again next Spring and lay eggs on new leaf growth.
4. Remove by hand or cut off all infected leaves and burn to break the cycle.