Question
What type herbicide can I spray on newly planted loblolly pine seedlings, planted in a field to kill existing wild grasses and bushes that will not kill the seedlings?

Answer
This is not a easy question with out knowing the type of weeds, grasses and brush that needs controlling. The soil type will also play into the recommendation. I would suggest that you contact the local office of the State Forestry Agency and ask one of their Foresters to come out and advise you on the proper recommendation for your needs.