Weeds on a ballfield
I am seeking information on how to get rid of problem weeds on a ballfield, namely broadleaf plantain and prostate knotweed. For a number of years I have sprayed these weeds with Roundup when they were growing vigorously. This method killed the weeds but later in the summer and the next year they were growing again. The ballfield surface is agra lime and currently the field is used very little. Does the inactivity on the field contribute to this problem since there is very little soil disturbance. Recently I tried to dig out the plants but due to the great length of the tap root many of the plant roots were only broken off and not entirely uprooted. I suppose these weeds will continue to grow. I am hoping that a vigorous dragging effort may help reduce the weed abundance so that when I spray in mid summer there will be fewer plants to deal with. I appreciate hearing what my best options are to get rid of these weeds. Thanks.
Lake County Minnesota
The vast majority of field managers use daily dragging and Roundup, when necessary, to control weeds on an infield.
The fact that you are not using the field on a regular basis, and as a result, not dragging it regularly, is definitely contributing to the weed problem.
Instead of re-creating the wheel, below is a link that takes you to an article by Dr. David Minner that deals exactly with your problem.
In Dr. Minner's article, he mentions pre-emergent herbicides and what their risks are to the players, but before buying a product, I would call your state pesticide registration office and check to see if any pre-emergent herbicides are registered to be applied in a baseball infield.