I think I might have leaf miners.

3 of my crops have big brown blotches running through their leaves.. chard, spinach, and beets. My turnips, lettuce, and parsnips are all fine.

One reference I have mentioned leaf miners on the three items I think I have them on, and recommends floating row covers.

Are there any other non chemical methods of control? I've picked the affected leaves off each day, but there seems to be so much of it!

Do you have any pictures? My beets were decimated by leaf miners last year. Terrible little things. I have read recently that you can try running your fingers over the leaf and gently squeezing to squish the little wrigglers. I'm not sure it would work, but may be worth a try to save some of your foliage.

No, but I did find a web site and the pics are identical to the damage done to my leaves. There are no visible bugs.. of course, I didn't look for anything inside the leave either.

this is put out by Safer brand.

http://www.saferbrand.com/advice/insect-library/garden-insects/all-about-leafminers/control-options

I will check this out.

What I am finding.. since I have a different crop in each square.. since my turnips are completely untouched.. the places where the turnip leaves overlap the spinach leaves or beet leaves are completely untouched... so maybe it is hard for the pests to identify the proper plant then? It is only where the chard, beets, or spinach are not next to another leafy green without problems....

So, next year, perhaps I will try one row with row covers, and then try blocks where the spinach, chard, and beets are completely surrounded by turnips and lettuce without row covers and see what kind of results I get. I'd prefer not to use row covers just because I can't see my "pretty" garden then.... all the turnips wouldn't be a bad things as I LOVE turnip greens (not to mention turnips).

Or I could alternate planting turnips and beets etc, all in the same block. Hmmm..maybe I've discovered a new companion planting pairing!