Weeds require soil moisture and nutrients just as do the pecans. Any period of drought stress on pecans is enhanced further by competition by weeds for that limited moisture.  Fertilizers applied to the pecans are used by weeds, thus adding to the expense of fertilizer use and potential for fertilizer deficiencies. 

The presence of weeds at harvest may also affect the harvesting efficiency of mechanical sweepers.  Weeds will prevent many pecans from being swept into the windrow, thus leaving pecans on the ground to either be wasted or require hand harvesting.

The standard weed management practices used for pecans in Georgia are a weed-free herbicide treated strip, 14 feet wide, along each tree row (7 feet on each side), and close mechanical or chemical mowing of the reminder of the orchard floor.  Use of a herbicide treated strip reduces much of the competition of the weeds. Close mowing of the remainder of the orchard floor allows for an added reduction in weed competition while retaining a sod for traction of spraying and harvesting equipment and reducing the potential for soil erosion.

A preemergence herbicide application should be made in the fall of the year (November 1 - December 15) to provide control of winter annual weeds and permit delayed use of a spring herbicide treatment.  The delayed use of a spring treatment insures that weed control is maintained for a longer period of the year.  Postemergence treatments may be required for control of perennial weed such as bermudagrass {Cynodon dactylon (L.) Pers.}, johnsongrass {Sorghumhalepense (L.) Pers.}, wild garlic (Allium vineale L.), and annual weeds that emerge after the breakdown of the preemergence herbicide. 

Orchard monitoring improves weed management by letting growers know when orchards need mowing and by identifying those difficult to control weeds that require special herbicide treatment.  Textural analysis of soil samples also aids growers in selection of the proper herbicide rate for their specific situation.