1

Some leaves show white patches or (fewer) holes. The main symptom to my eye are leaves that are tightly folded up along their main axes with both halves apparently glued together by some "foreign" substance. (One such folded leaf is depicted in the lower right part of the 1st image. An unfolded leaf is depicted in the 2nd image.)

I planted this Ipomoea relatively late in our season: it has grown fast but has no blooms (yet).

What (perhaps who) is this and how can I get rid the cause?

enter image description here enter image description here

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I wonder if you have leaf miners working to cause those tracks in the leaves. As they progress through their instars they spin silken threads which can fix leaves.

https://keys.lucidcentral.org/keys/sweetpotato/key/Sweetpotato%20Diagnotes/Media/Html/TheProblems/Pest-LeafChewingInsects/LeafMiners/Leaf%20miner.htm

  • Bedellia somnulentella (Zeller) indeed seems very plausible. The Wikipedia article indicates that this is also common in Europe, which is where I am based: It has a nearly cosmopolitan distribution and has been recorded from Russia, Ukraine, Georgia, southern Kazakhstan, Kirgizia, Uzbekistan, nearly all of Europe, the Middle East, Africa, India, Japan, North America, Australia, New Zealand and Oceania. – Drux Sep 3 '18 at 19:29
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This is possibly one of the many "leafroller" phenomena. A moth visits your garden and lays eggs. The eggs hatch and produce caterpillars that begin to feed on the foliage (you may see some leaf tissue damage on the plant). As they get larger they spin web cocoons to protect themselves as they develop into the next stage. The web is attached to the leaf and results in rolling of the leaf.

Usually there are few leaves affected and simply pulling the leaf apart to expose the caterpillar results in him dropping to the ground and becoming vulnerable.

There is a leafroller specific to the Ipomoea (Sweet potato/Morning Glory) family, but it could be one of many species.

  • +1 So I'll keep on pulling leafs apart plus watch out for possible web cocoons. BTW, so far I have never encountered a caterpillar in these folds, just those white patches, which are perhaps their traces. I'll add another image showing a freshly unfolded leaf. – Drux Aug 30 '18 at 4:30
  • I'm also curious about what biological mechanism (pathway) might let those leaves fold. It would seem to me that by folding up they expose themselves to their predator. – Drux Aug 30 '18 at 4:48

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