This the addition to the first post I did earlier today, when I took a closer look, still didn’t see insect, but noticed the leaves are eaten too.
I don’t see any damage to the leaves, but I do see a few cuts into the tips of the flowers. Yes, you have seen no insects or evidence of insects, such as webbing.
This was a puzzling question, thank you for posing it!
I sent it out to the full Ask a Master Gardener team and we were all quite fascinated by your situation. The team identified a few possibilities.
- If insects, it may be a species that can hide. That would suggest earwigs, the larvae of which could be deep in the trumpet. I suggest you cut open one of the damaged flowers and see if you can find something inside.
- The other insects that were suggested were leaf cutter bees, which leave a distinct half-circle shape cut out of the leaf or petal they bite. This is not harmful to the vine, just unsightly.
- It could also be Japanese Beetles, but they are usually highly visible, with shiny copper backs and bright emerald heads.
- But since there really doesn’t seem to be damage to the leaves, just the more tender petals, some of us thought that the problem is abiotic, that is, not caused by a disease or pest but by environmental factors such as drought, heat, excess sunlight, wind, etc. Recently I have noticed sun scorch on more plants than usual.
- But the winning suggestion may be “mechanical” damage, that is something bumping, crushing or tearing the flowers.
And the most likely culprit is a bird you would be delighted to have in your garden, otherwise — the beautiful oriole!
These brightly coloured birds are known to tear the blossoms apart in order to get to the nectar at the bottom of the trumpet.
So, what should you do? In addition to opening a flower to check for earwig larvae, you could purchase some sticky yellow cards from the local garden centre to see if you trap any insects, which could then be identified.
And certainly look out for the bright yellow or orange orioles. Here’s a picture: https://frametoframe.ca/2014/05/baltimore-orioles-toronto-backyard/
If you do spot orioles, the ideal action is to encourage them to visit your garden but leave the trumpet vine alone. Offer them an alternative source of food, using an oriole-specific feeder. Here’s some information from World Birds:
https://worldbirds.com/attracting-orioles/
Once again, thanks for contacting us, and instigating a very interesting research session.