PlantLife Online

Answer

Sounds like you have done everything you can for the large garden pests, mice, birds, and other rodents, my guess would be that it's something much smaller. Slugs or earwigs are the most likely culprits from the damage you describe and the steps you have take in previous years. Both do most their damage at night which also fits. To determine if you have either of these insects in your garden do some investigating. Turn over rocks, pieces of wood, under pots, any place that is moist that the earwigs and slugs may hideout during the day. Or you can go out at night with a flashlight and try to catch them in the act. If you determine there are slugs present they can easily be eliminated by sprinkling slug and snail bait around the garden. Earwigs can be controlled using home made traps, insecticide, sanitation or a combination. If you choose to use pesticides I recommend going down to your local garden center and speaking with someone that can point you in the best direction for your situation. Sanitation simply means removing the garden refuses and other objects earwigs like to hide in and under during the day.
Common Home Made Earwig Traps:
- A low-sided can, such as a cat food or tuna fish can, with 1/2-inch of oil in the bottom makes an excellent trap. Tuna fish oil is very attractive to earwigs.
- A rolled-up newspaper, corrugated cardboard, or short piece of hose. Place these traps on the soil near plants before dark and shake out the earwigs that accumulate into a container of soapy water in the morning and discard.

Always use pesticides at the labels recommended rate, more is not better and can enter ground water.

Hope this helps.