The Attack of the Spinach Leaf Miner

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It’s been the week of bugs attacking the greens. I brought home some lovely Swiss chard from a plant exchange at a friend’s place, and before long it looked like a mere shadow of its former self.

Something was chomping it down to the ground.

I couldn’t find any eggs around or larvae of any sort, so my first thought is it’s the pill bugs again.

Bugs on Swiss Chard

Last year they did the same thing to my peppers in the greenhouse. I dusted the entire section with diatomaceous earth to form a perimeter around the plants, and it looks like it’s helping. I just have to keep refreshing the DE anytime I water or when it rains to maintain that protective barrier.

Today I visited Laura, a gardening friend, who had an even more puzzling situation. Actually she has a couple of problems. She noticed holes and chewed edges on her Swiss chard, and thought it was the birds’ doing. She spread aluminum foil around the plants and contemplated a federal offense of whacking the feathered offenders until I told her I really didn’t think it was the birds.

With the Swiss chard, I thought she had the same issue with the pill bugs. They nibbled on them pretty good, but she said she noticed improvement after sprinkling the DE.

The other part was more bewildering. She told me she had tiny flies all over the place. There were dead ones in the water of the Wall-O-Waters and they were flitting all over the spinach, turnips, beets and other greens. And what threw me was the tiny were talking maybe a millimeter long white eggs on the bottom of the leaves. I almost had to whip out the reading glasses to see these things so I was impressed Laura was observant enough to find them.

Spinach Leaf Miner

I wasn’t sure what it was at first so I went to my all-time favorite horticultural site, Cornell University. It turns out Laura is dealing with the spinach leaf miner.

This is an insect that overwinters in the soil, and then the flies emerge in the spring to lay eggs to begin the cycle again. What Laura spotted (thankfully) were the adult flies, as well as the eggs (2-5 of them) deposited on the underside of the leaves. If she hadn’t have caught them, they would’ve emerged in 4-6 days with the maggots burrowing into the leaves.

In another couple of weeks her spinach and other greens would look absolutely terrible. Heres a good site with photos since thankfully we didnt have to go that far: http://ccesuffolk.org/assets/Horticulture-Leaflets/Spinach-Leafminer.pdf (the photo of the eggs is particularly good since they’re tough to spot).

To get rid of them Laura can pick off the affected leaves or give them a shot of horticultural spray or Neem oil. She’s been using a mix of a tea tree oil solution in water, which appears to work, although theres greater risk of burning the leaves of the plants. Once she eliminates the eggs she should have them under control for the year, but its important that she doesnt put another crop in this same space next year to avoid a reoccurrence.

Meet Amy Grisak

Amy is a freelance author and photographer in Great Falls, MT who specializes in gardening, foods, and sustainable agriculture. She provides information on every kind…

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