I took this from a site I found, but the advertising content at that site could be deemed inappropriate so I'll just do an excerpt. There are several things that could be causing your damage. Hope this helps.
Living factors such as insects can wreak havoc on plants, and it can be hard to detect which insect is causing the damage. Location and type of damage are two important clues that will help a gardener determine if the damage is caused by an insect and which insect. An insect's lifecycle also plays an important part in identifying which insect and finding a solution to the plant destruction.
Plant Inspection for Chewed Damage
If the entire leaf has been consumed, with only the middle vein remaining, look for caterpillars, canker worms, or webworms. Notches that appear to be cut from the leaf are a sign of adult black vine weevil, while circular holes might be caused from lead cutter bees. Smaller holes in a random pattern are the work of beetles, weevils, grasshoppers, or chafers).
On leaves that have veins showing and little else, a gardener should look for slugs, elm leaf beetle, beetle larvae, and thrips (a small sucking insect). Leafrollers (insects who make nests by rolling up in leaves) are the offenders of leaves that are rolled up or joined by silken threads.
An insect that feeds between the upper and lower surfaces of a leaf is the leaf miner. If a gardener holds the leaf up to a light, they will be able to detect these insects inside the damaged area of the leaf. Small moth or sawfly larva can burrow into the petiole (a thin stem which supports the leaf blade), causing the leaf to drop off in early summer. These are detected by splitting the petiole for inspection and identification of the specific larva that may exist.
Insects that girdle (continuous section cut all the way around a twig or small branch) are usually a vine weevil or twig girdling beetle. Borers that feed under the bark can be detected by holes in the branch, a decline in the plant overall, and even frass (debris or excrement produced by insects). Know culprits are the pine Zimmerman pine moth, beetle, and raspberry crown borer.
