Allright,you want to kill these fukin trees right now without a bunch of maybe shit,you need a product called "Round up Tree & Brush Killer",that shit will defoliate a mighty oak tree in a few weeks with no guess work,ive done it several times & will be doing it this year as well .
Take a cordless drill with spare batteries & a 1" spade bit,you'll also need a long neck funnel for each tree you want to drop & zip lock baggie for each funnel.
Drill a hole at the base of the tree at a severe angle as deep as you can,you can buy auger drill bits that can cut a 12" inch depth at Home Depot,put the funnel in the hole & fill it up with Round up,then cover the top of the funnel with the zip lock bag & secure it,within 24 yours the funnel will be empty & the tree well on its way to defoliating.
Fill the funnel every few days for a few weeks & that tree will not grow one single leaf & it will brown out & die looking very natural.