This study consisting of six field experiments was conducted in 2018 and 2019 to evaluate the tolerance of four corn hybrids (P9998AM, P9840AM, DKC42-60RIB, and DKC43-47RIB) to the tank mix of tolpyralate + atrazine with a commercial glyphosate formulation. At 1 wk after application (WAA), two corn hybrids (P9998AM and P9840AM) exhibited more injury from tolpyralate + atrazine (2× rate) applied alone and in combination with glyphosate than DKC42-60RIB and DKC43-47RIB; however, all corn hybrids responded similarly with respect to visible injury 2, 4, and 8 WAA, stand loss, and yield. Application of tolpyralate + atrazine or glyphosate + tolpyralate + atrazine at the 2× rate caused greater corn injury (up to 27%) than tolpyralate + atrazine or glyphosate + tolpyralate + atrazine at the 1× rate (up to 8%) at 1 WAA. The addition of commercial glyphosate with tolpyralate + atrazine did not enhance injury symptoms. Results of this study show that there is a wide margin of corn safety with tolpyralate + atrazine applied alone and in combination with a commercial formulation of glyphosate.

Creeping bentgrass creates a dense, high-quality playing surface on golf courses, but it often encroaches adjacent areas of Kentucky bluegrass. Mesotrione can control creeping bentgrass in Kentucky bluegrass, but more information is needed regarding the effect of herbicide rate and number of applications on creeping bentgrass control and the impact to Kentucky bluegrass. Field experiments were conducted to determine the effect of application rate and number of applications on creeping bentgrass control. One application of mesotrione controlled 7 to 43% of creeping bentgrass in Kentucky bluegrass, and two applications of mesotrione controlled 39 to 88% as rates increased from 70 to 1,120 g ai/ha. Gaps present in the canopy after the creeping bentgrass died reduced overall turfgrass quality 2 to 6 wk after treatment (WAT) before recovering. These data indicate the capability of mesotrione to selectively control creeping bentgrass while providing excellent safety to Kentucky bluegrass.