Mowing Timing Doesn't Affect Common Broadleaf Herbicide Efficacy.

Current recommendations for systemic broadleaf herbicides are to withhold mowing 2 days before or after an application. However, professional applicators often have little control over mowing. Our objective was to determine how mowing around an application affects the efficacy of 2,4-D + MCPP-p + dicamba on common dandelion (Taraxacum officinale F.H. Wigg.) and white clover (Trifolium repens L.). Research trials in Manhattan, KS (KS) and Mead, NE (NE) were initiated in Kentucky bluegrass (Poa pratensis L.) in October 2016. Approximate dandelion cover was 50% in KS and 20% in NE. White clover was also present in NE, and initial cover was approximately 20%. Treatments were arranged in a 2 (herbicide) ×10 (mowing timing) factorial in a randomized, complete-block design with four replications. Herbicide levels were a single application of Trimec (1.1 kg 2,4-D ae ha^-1 + 0.3 kg MCPP-p ae ha^-1 + 0.12 kg dicamba ae ha^-1) or untreated. To achieve mowing timing levels, plots were mowed at 7.6 cm 4, 3, 2, or 1 days prior (DP) to application, immediately prior to application, immediately after herbicide was dry following application, or 1, 2, 3, or 4 days after (DA) application. Percent cover of dandelion and white clover was collected from 0 to 24 weeks after treatment (WAT). The herbicide by mowing timing interaction was never significant, nor was the main effect of mowing timing. Averaged over mowing timings, herbicide treatment resulted in 3% dandelion cover compared to 64% cover in untreated plots in KS. Similar results were observed for dandelion and white clover in NE. Mowing Kentucky bluegrass at 7.6 cm from 4 DP to 4 DA an application of Trimec does not affect control of common dandelion or white clover.