Package check result: NOTE

Check: CRAN incoming feasibility, Result: NOTE
  Maintainer: ‘Bart-Jan van Rossum <bart-jan.vanrossum@wur.nl>’
  
  Found the following (possibly) invalid URLs:
    URL: https://wheat.pw.usda.gov/ggpages/SxM/
      From: inst/doc/IBDCalculations.html
      Status: Error
      Message: server verification failed: certificate signer not trusted. (CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none)

No changes to worse in reverse depends.