It is best to keep food plots free of unwanted plants (weeds & grasses) to maximize forage production.
The use of herbicides is a great tool to alleviate weed problems. First the field should be kept clean to ensure that the unwanted plants are not able to seed out.
It is important to identify the primary plant species you are trying to control. It is much easier to kill weeds at an early stage than to wait.
Pre-emergent herbicides will help stop a majority of the weeds from becoming established. If the problem persist, apply a post-emergent herbicide to control existing weeds and grasses.
Herbicides can usually be purchased in both spray and granular form. It is very important to know what type of plants the herbicides will control.