Something is damaging the leaves of my chard plants. There are blotches that appear as if the green surface has been scraped or eaten away, and there are sort of squiggly tunnel-like markings. Is this caused by an insect? Should I remove the plants and not plant chard in the same spot next time?
What you are describing sounds like leaf miner damage. Compare what you are observing to the particularly clear photos from this University of Connecticut extension fact sheet. See also this Washington State University Extension page about leaf miners on spinach and beets. Here is an excerpt:
“Control weeds in and around the garden. Rotate crops. Do not replant where crops were infested the previous year. Pinch leaves to kill larvae inside. Pick out infested leaves when noticed. Discard leaves in garbage. Screen plants with a floating row cover prior to emergence of flies in spring (April-May).”
You don’t need to remove the plants entirely–just cut off the damaged leaves–but you should plant your chard (and spinach and beets) in a different part of the vegetable garden next time.