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I have an artichoke planted in a raised bed in southern California, USA.

The new leaves at the core look healthy and happy, but the biggest, oldest, outermost leaves develop white squiggly lines. At first it's just a few, but eventually the leaf becomes covered with them, dies, dries out, and falls down to lay in the dirt.

The lines are not deposits on the surface of the leaf. They appear to be dead spots within the leaf, visible from both sides. It looks almost like something has been crawling on or inside the leaves and scraping them, but I never find any visible pests on the plant.

What is causing these lines and what can I do about it?

Damaged artichoke leaf

Sue Saddest Farewell TGO GL
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Robert
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  • looks like leafminer damage, although those tracks are a lot smaller than the one's I get on my lime tree – WebChemist Apr 09 '14 at 20:08
  • Yeah. Those look like leafminers, although they look more sporadic than the ones in our grape leaves. I've heard that silica can help to strengthen leaves (and make them more resistant to pests). So, I watered our grapes with some diatomaceous earth. We'll see if it helps for next year. Also, I think our Siberian elm tree may have spread the leafminers to our grapes, initially. I wonder if cutting it down, as we intend, will help. What plants or trees are near your artichoke? They say leafminers don't pose a threat to the plant, but I'm sure plants do well without them. – Brōtsyorfuzthrāx Oct 10 '14 at 02:11

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I agree - it's leafminers. There are several kinds of insects with larvae that do this sort of damage, but one thing they all have in common is they are rapidly becoming resistant to the usual chemical controls. Non-chemical controls consist of removing infected leaves, and/or plants, keeping dead leaves and debris scrupulously picked up, rotation of crops, trapping and killing the adults before they can lay eggs, picking off eggs from underneath the leaves, and trying to make the area more attractive for the leafminer's predators so they can do a better job of keeping them in check. Identifying the type of leafminer may be of some value - most likely the one you are seeing on your artichokes is the Chrysanthemum Leafminer. A pest management publication by UC Davis says it is rarely a cause for treatment, but it depends on how much damage you are experiencing.

TeresaMcgH
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  • That was very helpful. I think you are spot-on about the Chrysanthemum Leafminer. I think I'll try the non-chemical controls you suggest. Thanks! – Robert Apr 09 '14 at 23:43
  • Do they similarly develop resistance to neem oil? It sounds like it helps for leafminers on tomatoes. See http://gardening.stackexchange.com/questions/13706/what-are-these-lines-on-tomato-leaves?rq=1 – Brōtsyorfuzthrāx Oct 10 '14 at 02:14