Sequential applications of preemergence and postemergence herbicides for large crabgrass (Digitaria sanguinalis) control in tall fescue (Festuca arundinacea) turf

Preemergence (PRE) and postemergence (POST) herbicides were sequentially applied to tall fescue over a 2-yr period to determine the lowest herbicide rates needed for acceptable large crabgrass control. Prodiamine was the only PRE herbicide that provided full-season large crabgrass control in tall fescue turf. The control was 85% in plots treated at one-third recommended rate (0.3 kg/ha) and 96% at the full rate (0.8 kg/ha). Sequential applications of oxadiazon at one-third recommended rate (1.1 kg/ha) in late February followed by fenoxaprop (0.2 kg/ha) in June controlled 85% large crabgrass in late August. Control was similar in mid-August when pendimethalin, dithiopyr, or oryzalin at one-third recommended rates was followed by fenoxaprop, but was not acceptable (less than or equal to 74%) by late August. In most instances, large crabgrass control was higher when fenoxaprop followed the PRE herbicide application than with MSMA. Reduced herbicide rates may not provide full-season large crabgrass control in other areas with different soil and weather conditions. Tall fescue quality was not affected by prodiamine, dithiopyr, and oxadiazon. In 1996, pendimethalin at 3.3 kg/ha reduced turf quality 16% and oryzalin at 2.2 kg/ha reduced quality by 46%. In 1995, MSMA reduced the quality of tall fescue more (less than or equal to 21%) than fenoxaprop (less than or equal to 10%). When compared to the use of PRE and POST herbicides alone, sequential PRE plus POST herbicide programs did not affect turfgrass quality.