Oak tree and fruit trees

Hello again, i have an issue with little, lime green caterpillars that descend upon my fruit tree sapplings from some mature oaks every season, any idea what they are and how is best to prevent this from happeninf without chemical if possible?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.