Change to a liquid.
For St Augustine lawn [assume its floratam - most common variety]
You can get Atrazine at walmart; however you must read the directions on
temperature. The brands that come in the white bottle have a white
powder-like stuff in it which can dry and plug up your sprayer bottle
It can be applied no more than once a month. Lawn only; use a
glyphosate like roundup in gardens
Its effective only when they are growing.
Its best to apply in the evening, [2nd choice-early am] 2 days before a
rain [or using your sprinkler system]. Figure out your square footage.
I use a hose end sprayer [labeled for weeds]- the simple kind like at
Other grasses - weedbgone [the big refill tells which grasses are safe]
And it comes in a bottle that you can attach to your hose. Strong
Chances are there are oodles of seed just waiting to germinate.
I have a pair of rubber boots just for weed spraying