Look what I found on several of my panicle hydrangeas: WEB WORMS!
HYDRANGEAS AND FALL WEB WORMS
First time in 28 years these beasties have shown up. Don’t know if it’s because of our unique summer conditions, or some other plant that had them and they migrated over, but now that they are here, what should I do?
WHAT’S GOING ON HERE
The good news is I don’t need to do much. Web worms are practically harmless, although pretty disgusting to look at and somewhat alarming to view. Here’s technically what’s going on.
A moth lays some eggs on the foliage during the summer. Those eggs hatch into worms that then create a cocoon-like web to rear their young until they are ready to leave the nest.
WHAT TO DO ABOUT WEB WORMS
The net of it is you can just leave it alone and open up the nest with a stick to let the birds feed on the worms. A second solution is to cut off the stems of the plant and put them in the trash. If the worms are still feeding, you could treat organically with Bacillus thuringiensis var. kurstaki (Btk)sold as Dipel or Thuricide. But if the caterpillars are gone, forget the sprays: the insecticide is useless. I prefer not to use an insecticide in this case regardless. I like the low-tech approaches of opening up the webs or removing the stems if there are just a few and I can reach them.
IMPACT ON YOUR PLANT
All of this happens so late in the season that the impact on your plants is mostly cosmetic. But your plant has been stressed so treat it well until it goes dormant, making sure it gets watered if dry spells occur. Do not fertilize but feel free to add compost – that’s always a good thing.
Look around your garden. Web worms feed on plants other than hydrangeas and it’s likely you have them somewhere else.
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