Georgia,
United States 
I have 18 round shaped Youpons (shrubs) planted/aligned (20 years ago) in front of my home.They have been shaped continuously and are 5'x5' each. One Youpon seems to have blight. I will be cutting all of them down (BEFORE SPRING) to about 1' to get new growth. They have been shaped. The soil has not been aerated/ or ammended and has been compacted since planting. Can I amend, aerate/cultivate soil around pruned Youpons with a Mantis Tiller to a depth of 10" or will I destroy the roots? Houzz has never replied after 2 months!!! SORRY SO WORDY, BUT I NEED ADVICE BEFORE I DO SOMETHING WRONG. THANKS
7 Feb, 2018
Answers
What sort of blight are you thinking of, Novice? There are several diseases that affect Yaupon, but none are just named "blight".
8 Feb, 2018
For non USA folks a Youpon (aka Yaupon) is Ilex vomitoria, a type of native Holly.
I don't think it would be a good idea to go that deep round the plants as feeding roots for most shrubs are in the top 4 or 5 inches.
If you need to aerate the soil and get some nutriments in then you would be better doing it manually with a hoe and only going 2 inches down.
Mulching with organic material would help as this would encourage worms who would aerate the soil for you.
7 Feb, 2018