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Controlling Leaf Miners

September 10, 2008
Mined Rainbow Chard Leaves

Mined Rainbow Chard Leaves

If you’re growing chard, spinach or other leafy greens in Seattle this month, you may be seeing widening lines of twirling damage running through your crops. Fall and Spring seem to be the season for the leafminer to go crazy on our food crops. And, they’re tough to remedy.

Leaf miners are small maggot creatures that live in the mid-tissue layer of plant leaves. They “mine” out the nutrients in a rapidly-widening path that skeletonizes plant leaves. If you break open the remaining layers of the leaves, you may find a tiny maggot wiggling around in its speckled black poop. You may find that the worm has turned into a pupae or the pupae has hatched and flown away.

Mined Leaf with Exit Hole

Mined Leaf with Exit Hole

How to get rid of them? Hopefully you have parasitic wasps that will do the work for you (another reason not to spray bee-killing insecticides in the garden!) But, if your leaves are being mined already, then you need to get to work removing and destroying the affected leaves. If you remove the leaves early, you avoid the chance that another crop will destroy additional leaves on the same or other plants. Plus, if you let the leaves remain, you may infect your soil with pupae, bringing on a fresh crop of problems next spring.

Can you spray? Please don’t. Because leaf miners live inside the layers of the leaves, its unlikely that a spray application will even affect them. And if a product promises that it does kill leafminer larvae, keep in mind that it must have the ability to penetrate the cell layers of the leaf that you plan to eat. 

Close Up of Mined Rainbow Chard Leaf

Close Up of Mined Rainbow Chard Leaf

Too, there are some weeds like plantain and chickweed that serve as host plants for this pest. Be vigilant in removing them from your garden.

Oh, and when you cut off a leaf of infected chard or spinach, you can eat the part that hasn’t already been eaten by the miner. Just tear the good part away and toss it in your salad. Share and share alike!

Now that you’ve harvested all those leafy greens, here’s a quick recipe that you’re bound to enjoy:

Ingredients:

  • Leafy greens like spinach or chard, torn into pieces with mid-ribs removed
  • Mid-ribs of leafy greens, chopped
  • 1 onion, chopped
  • 2 cloves garlic, chopped
  • 1 tomato, cut in wedges
  • olive oil
  • dash red pepper flakes or fresh ground black pepper
  • 2 T. soy sauce

Heat olive oil in large saute pan or wok. Add chopped mid-ribs of greens and onion. Saute over medium heat until slightly browned. Add garlic and red pepper flakes and saute briefly. Begin adding chopped greens, tossing to wilt. As each batch starts to shrink, add another batch. Try not to overcook. When all are slightly wilted, add soy. Remove from heat and toss with tomatoes.

Take that Leaf Miners…you never had it so good!

6 Comments

  1. [...] their eggs, which hatch into decimating green worms. Row cover can also help keep other pests like leaf miner off of spinach, beets and chard. And, if you’re lucky, it can keep carrot fly off the [...]

  2. [...] to get brown spots or ‘tracks’, remove the leaf immediately. You’ve got ‘leaf miners‘ and left alone they’ll rapidly ‘mine’ your entire crop! I actually lost [...]

  3. Allen olsen says:

    I have a nursery in northwest Montana and just about every single aspen tree in Libby has been affected but the leaf miner. All the aspen are so bad they all look white. Do you have any answers for this? I do like to spray and they are in great big mature trees. Please e-mail me back with a possible answer. My e-mail (removed by editor) Thank You Allen

  4. Allen, I’m not sure how to manage leaf miner on Aspens. It sounds awful. Try contacting a certified arborist in your area via the ISA.org site for help. Best of luck!

  5. Sheelagh Oliveria says:

    In regard to the leaf miners on the aspens, encourage moth eating birds. also plant aster family plants that bloom well into fall to feed predatory wasps. it’s amazing what a stand of flowers will do to protect gardens. it’s all invisible too. just healthy plants. can’t have health And poisons. gotta choose one.

  6. Sheelagh, thanks for sharing your recommendations.

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