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Under the Arbor Issue 29
June 25, 2022

In This Issue:

~ Creepy Crawly du Jour: Leaf Miners ~

~ The Best Use of Epsom Salts ~

Sorry the newsletter's late, I'm down with the dreaded 'vid. Not too bad, but sleep, mandatory duck chores and watering have been all I can manage. Sometimes you just gotta go with the flow and surrender…

Leaf Miners

Ever wonder about those squiggly lines that form on your chard or petunia leaves? They are caused by leaf miners, which are the insect larva of certain species of flies and moths.

The fly (or moth) injects its eggs with one end between upper and lower "skin" layers (epidermis) of the leaf, where the larva that hatches munches its way around inside the leaf while remaining safely protected from predators. It's a great strategy - from their point of view. They are "snug as a bug in a rug", as the saying goes.

Photo collage clockwise from upper left: 1) Mama fly laying a single egg 2) A cluster of eggs she laid on red chard leaf 3) A calendula leaf with active leaf miner larva inside 4) Green chard leaf with epidermis torn away to expose the larva.

But that's not the end of the life cycle…

When they have eaten their fill and gotten nice and chubby (takes a couple of weeks), the larva chew through the lower epidermis and drop to the soil, where they burrow in for another 2 or 3 weeks until they turn into flies (or moths, if that's what their mom was), ready to mate and lay eggs on some more of your plants.


As I've written before, I'm careful about using the word "control" in the garden, because humans' heavy-handed attempt to make everything bend to our will is… well… destroying life on Planet Earth. We need to learn to work with life instead of trying to "outwit" and dominate it.

So I don't recommend poison sprays, because from an overall garden ecosystem perspective, they will cause more imbalance and trigger unforeseen problems down the road.

My first line of defense against leaf miners is Reemay or Agribon floating row cover. This is not a one-and-done, however, because as the flies emerge from the soil (where they overwintered as pupae), they will be trapped under the row cover with your plants.

In my experience, they do seem to hatch all at once, because one day there are no flies and the next day when I open the tent to peek in, there are a whole bunch all ready to fly away. Subsequent days very few.

I inspect the underside of my chard leaves every day or two and squish any little white eggs I find before replacing the row cover.

Neem oil can be effective too, but it is rather broad spectrum across species. It doesn't kill things outright, but it makes their behavioral hormones go all kattywompus, so they can't figure out how to dress up for a date, or mate or lay eggs. Neem is a naturallly occuring oil from the Neem plant.

To recap: 1) Use floating row cover, but check under it daily till flies hatch and then let 'em escape (or spray with Neem) and re-cover. 2) Look for and squish the eggs 3) Squish the larva inside their tunnels 4) Sit in your garden with a cup of coffee, and accept that sometimes things aren't perfect, and you can enjoy the dance anyway

In my garden, in the past, leaf miners have always favored my chard. But this year is different than any other in my gardening decades. Leaf miners are in my lupine, and many other flowers, even in the harmless purslane weed that I allow to grow low to use a a living mulch.

Life just seems to be messed up and lots of different bugs and things are appearing in greater numbers and across different plants.

Buckle up. Focus on living by your heart's values, do your best and let go of the rest.

The Best Use of Epsom Salts

There is SO much manure out there about using Epsom salts in the garden it makes me wanna slap my forehead! Soil mineral balance is a complex dance, and if you're not aware of its complexity it's easy to fall into this simplistic internet meme and seriously damage your soil…

Then again, it could be just the ticket! The point is, you don't know without a soil test.

While magnesium and sulfur are both necessary plant nutrients, without a proper soil test and some understanding, the indiscriminate use of Epson salts can cause irreparable damage to your precious soil.

It all depends on whether your soil is deficient in magnesium or sulfur, and whether or not all the other minerals in your soil are present in the correct ratios to one another. If too much of one mineral skews the ratio, it can actually prevent the uptake of other essential minerals that are present, but that have now been rendered inaccessible.

The takeaway is that without a complete, detailed and accurate soil test (that is, NOT one from your State University Extension Service) you have no idea whether Epsom salts may be beneficial or not. And, like dumping too much salt in your soup, how will you get it back out if it's too much? The Land Grant Colleges (now State Universities) across the US are heavily funded by the fertilizer industry, and the soil tests performed by their State Extension Service are limited in scope and aimed at arriving at a commercial fertilizer prescription. Home tests are also too limited.

I recommend soil testing through Logan Labs in Ohio, because they use a very strong extractant and give very accurate and detailed results (in case you're wondering, I do not get a commission, and there's a link to more info further down).

Now if for whatever reason you don't want to do a soil test you can use a balanced, complete organic fertilizer, which will not correct imbalances in your soil, but it will support this year's crop.

However, if you're serious about growing for maximum nutrition, plant health and disease resistance, I highly recommend sending off a soil sample and beginning to work on slowly correcting any soil mineral imbalances. For more information about soil testing, designing mineral fertilizer prescriptions that you can figure out yourself based on a proper soil test, as well as a recipe for mixing a complete organic fertilizer, click here. In the meantime, best steer clear of Epsom salts.

Except for their best use: in your bath water after a long day working in the garden!


Vegetable Garden Guru is dedicated to the renewal of regenerative, sustainable, organic vegetable gardening around the world. May we become gardeners of healthful, nutrient-dense food, careful stewards of soil, and may the plants we tend remind us to always keep growing toward the Light.

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