Thank you for your condescension: Interesting that you think I can decimate birds but not weeds, but we can let that one go I suppose.
You don't need to 'let it go'. You could just admit that you're wrong.
And don't try to back up your suppositions by using the thesaurus:
Synonyms of "decimation" from Merriam-Webster, Bill. Are you ready?

annihilation, destruction, demolishment, demolition, desolation, devastation, extermination, extinction, havoc, loss, mincemeat, obliteration, ruin, ruination, wastage, wreckage
A thesaurus gives words 'similar in meaning to' the chosen word. This is to allow you to choose the most suitable word. The words in any particular group are not all interchangeable.