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Bispyribac-sodium (Velocity®) is labeled for control of Poa annua (L.) and Poa trivialis (L.) in creeping bentgrass (Agrostis stolonifera L.) and perennial ryegrass (Lolium perenne L.) fairway turf. Previous research has documented that Velocity may elicit some objectionable yellowing to desirable turfgrass species and that tank-mixing Velocity with a 12% iron (Fe) product may mask some of the turf discoloration, however additional work is needed using other
products and to determine if the addition of Fe and other foliar nutrients might impact herbicidal activity.
This study was conducted on a fairway maintained at 0.5 in height, located at Brookside Country Club in southeastern Pennsylvania, and comprised of approximately 80 to 85% creeping bentgrass and 15 to 20% Poa annua. Visual ratings included creeping bentgrass and Poa annua injury (0-5 scale with 0= no injury, 2.5= to thinning and yellowing and 5=brown dead turf), and percent bareground (0 to 100 scale with 0 = no live turf, and 100 = entire plot area covered by green and healthy turf). The objective was to determine how fertilizer treatments applied in combination with Velocity affect herbicide activity, creeping bentgrass safety, and species competition within the sward.
Herbicide efficacy was significantly affected by each of the foliar fertilizer treatments on only one rating date, June 26, 2007 (Figure 1), and was largely unaffected by the type of fertilizer applied in combination with Velocity. Creeping bentgrass safety increased with the use of foliar fertilizers and specifically the Iron Combo (1-0-2 plus 4.5% Fe + 0.1 % Cu, 1% Mn, and 1% Zn) and Irontech (4% Fe + 0.1 % Cu, 1% Mn, and 1% Zn) treatments, which were often similar to the untreated control. The Gary’s Green (18-3-4 plus 0.12% Cu, 1% Fe, 0.1% Mn, and 0.1% Zn) + 5% Iron Chelate combined with Velocity treatment only provided significant creeping bentgrass safety on two rating dates, June 20 and June 30 (Figure 2). The percent Poa annua in plots was similar for all treatments and significantly different from untreated plots. On July 6 a significantly higher percent of bareground occurred for the Velocity alone treatment compared to the Velocity plus foliar fertilizer treatments, while a higher percentage of bareground existed for the herbicide plus fertilizer treatment than the untreated control (Figure 3). Three weeks later, however, the herbicide plus fertilizer treatments contained the same percent bareground as the untreated control (Figure 3).
The results from this study indicate that, in general, the use of foliar fertilizers containing iron, nitrogen, and micronutrients will not negatively affect the activity of Velocity when managing Poa annua, and that Iron Combo and Irontech provided the greatest safening effect for creeping bentgrass. This would indicate that besides the positive effect of Fe, fertilizers containing higher percentages of Mn and Zn may be contributing to increased plant safety. In
addition and importantly, the use of foliar fertilizers in combination with Velocity will have a positive effect on the competitiveness of the creeping bentgrass causing it to propagate into voids left behind by Poa annua that has been eradicated by the herbicide. A similar research protocol will be conducted in 2008 to corroborate these findings.

Figure 1. Annual bluegrass (Poa annua) injury after treatment with Bispyribac (Velocity) alone and a combination of Velocity plus foliar fertilizers.

Figure 2. Creeping bentgrass injury after treatment with Bispyribac (Velocity) alone and a combination of Velocity plus foliar fertilizers.