Mapping the weeds in your crop fields can provide you with a

valuable tool for dealing with these problem plants in the future. Mid- to late summer is a good time for weed mapping, says agronomist Denise McWilliams of the University of Minnesota Extension Service.

"Weed mapping can be simple or high-tech," says McWilliams. "You can use a global positioning system and spatial analysis computer software, or pencil drawings."

Mapping weed locations will allow you to check for yield loss due to weeds, says McWilliams. A combine with a yield monitor can be helpful for this. Maps also provide a way to find weed problem areas next year and plan tillage or herbicide control measures.

"Scouting fields for weed pockets and comparing summer weeds with early season weeds can show you how well your weed management program worked this year," says McWilliams. "And by maintaining a record of weed problems over the years, you can further refine your control strategy to get the maximum payoff for your weed control efforts."