I'm not aware of any insurance companies that insure standing timber. It would be prudent, however, to make sure you have a current timber basis (i.e., a recent forest inventory and appraisal) in case you were to lose these trees due flood, drought, tornado, etc.
In that particular case, you would be able to take a casualty loss on your federal taxes, but only if you know the value of your trees. Most professional consulting foresters provide timber / land appraisals.
Iowa Consulting Foresters: https://www.extension.iastate.edu/forestry/publications/PDF_files/F-361.pdf