Please do not kill the caterpillars. Pretty please?? You can hose down the tree to wash the soap off.
These are not worms; they are caterpillars. Butterflies lay their eggs on host plants so when the eggs hatch the caterpillars will have food to eat. The caterpillars will develop through several instar and when they are full sized, they transform into a chrysalis. The chrysalis will then turn into a butterfly.
Hop trees are host plants for the Giant Swallowtail Butterfly along with Rue, Orange Trees, Prickly Ash and citrus. They do not kill or hurt your tree.
