When making my yagis I prefer plugging yagi dipole ends so water cannot run down the tube and enter the dipole housing with its corrosive end results. Also, it does stop spiders moving in and making a right mess everywhere.
Many people do not like to add caps to the elements for concerns over altering resonance, so I just cut the cap off and push them in so they are fully inside but water cannot enter. Simples.
These plugs were from nuxcom.de but he has ceased trading now but they are available at various places including Tino’ Funkshop but these days if you are in the UK it’s best to look more local.