Should we leave these caterpillars be?
Our tenants sent these two pictures of caterpillars on our door frame and on our burning bushes. They are eating the bushes bare. He wanted to know if hosing them down with water will work....or do I need to hire someone to come out(or let them be if they are harmless)? Thank you for any help you can give!
These are a fairly new alien invasive insect, the euonymus leaf notcher: http://extension.umd.edu/hgic/invasives/euonymus-leaf-notcher
These caterpillars are finishing up their eating and are now wandering away to pupate (make cocoons). It is too late to spray them this year.
Your euonymus should be able to grow new leaves this year, but the shrubs will not be able to continue doing so year after year if the caterpillars continue yearly--as they probably will. The plants get weaker and weaker.
You need to spray the caterpillars with Bt next year as soon as the caterpillars appear next spring, before they do a lot of damage. Also, Bt is primarily effective when caterpillars are young and small.