I am growing hops for the first time this year. I planted 3 Chinooks and 3 Willamettes this past spring. The Willamettes are growing really well but have not flowered. The Chinooks are flowering and I may have enough for a couple of batches this fall. My question is, when I went to water them today I noticed several caterpillars on the bines. But, only on the Chinooks. Nothing was on the Willametts. They are 1-1.5" long, and somewhat colorful with spines sticking up. What are they? Are they harmful? What do I do about them? I live in the Kansas City area, if that helps. Steve
Caterpillars eat a lot of foliage in general, don’t know about hops. I would pick them off and relocate them someplace else.
They are Eastern Comma Butterfly (a.k.a. “Hop Merchant”) caterpillars. They were a crop limiting pest when hops were grown on the East Coast. Hop merchant caterpillars are easy to eradicate compared to Japanese beetles. They can be removed by hand or hit with organic insecticide. The Eastern Comma Butterfly is beautiful.
http://www.uvm.edu/extension/cropsoil/hop-pest-eastern-comma
Can I relocate to another host plant?
I would take them far enough away that they won’t get back to your hops.
Are you located near a river or bottomland? The Eastern Comma’s native habit is woodland nettle. The nettle grows in moist woodlands.