FALL APPLICATION OF PRODIAMINE FOR SPRING CRABGRASS (DIGITARIA SPP) CONTROL

Fall application of a PRE herbicide offers professional lawncare appli cators additional flexibility in scheduling necessary weed control ope rations. A 3-yr field study was established on common Kentucky bluegra ss in Urbana, IL to examine the effectiveness of fall- or spring-appli ed prodiamine and DCPA for spring large and smooth crabgrass control. Prodiamine was effective for crabgrass control in turf (greater-than-o r-equal-to 91% control) when applied in spring at greater-than-or-equa l-to 0.4 kg/ha or when it was applied in the fall at greater-than-or-e qual-to 0.6 kg/ha (greater-than-or-equal-to 82% control). In most case s, fall-applied prodiamine at the 0.8 kg/ha rate (greater-than-or-equa l-to 91% control) controlled crabgrass as well as spring-applied DCPA at the 11.8 kg/ha rate (greater-than-or-equal-to 94% control). Little reduction in turf quality (greater-than-or-equal-to 8.3) occurred when prodiamine was applied in the fall at 0.8 kg/ha or less. Only when pr odiamine was applied at 2.2 kg/ha was there significant quality loss ( 7.3) with spring applications. In a second experiment to evaluate spli t fall and spring prodiamine applications for crabgrass control, all s plit applications had 100% crabgrass control which was not significant ly different from single applications of greater-than-or-equal-to 1.4 kg/ha. Nomenclature: DCPA, dimethyl 2,3,5,6-tetrachloro-1,4-benzenedic arboxylate; prodiamine, 4-dinitro-6-(trifluoromethyl)-m-phenylenediami ne); large crabgrass, Digitaria sanguinalis (L.) Scop. #3 DIGSA; smoot h crabgrass, Digitaria ischaemum (Schreb. ex Schweig.) Schreb. ex Muhl . # DIGIS; Kentucky bluegrass, Poa pratensis L. #POAPR.