GROUND IVY CONTROL AS AFFECTED BY MOWING PRIOR TO OR FOLLOWING HERBICIDE APPLICATIONS. A.J. Patton* and D.V. Weisenberger, Purdue University, W. Lafayette, IN (98)
Extension bulletins and turf herbicide labels often recommend not to mow turf 24 hours before or after application of a herbicide to maximize weed control. However, the effect of mowing on herbicide efficacy has not been sufficiently explored. The ability to make a herbicide application soon after mowing or prior to mowing would give turf managers more flexibility in scheduling applications and help lawn care operators who often make herbicide applications to lawns but do not have control of the mowing schedule for these properties. The objectives and this research were to 1) determine which herbicides most effectively control ground ivy (Glechoma hederacea), 2) determine the effects of mowing on ground ivy control, and 3) determine if any herbicide by mowing timing interactions exist. The experiment was arranged as a 3 X 6 factorial with main effects of mowing timing and herbicide selection. Individual plot size was 2.25 m2. Three mowing timings included mowing 30 minutes before application, mowing 30 minutes after application, and no mowing 72 hours before or after application. These mowing treatments were designed to simulate a worst case scenario of mowing either immediately prior to or after a mowing. Plots were mown at 5 cm removing 1.3 to 3.8 cm of Kentucky bluegrass (Poa pratensis) leaf tissue. Ground ivy was dispersed through the turf canopy at heights of 1.3 to 7.6 cm prior to mowing and the mowing treatments removed approximately 30-40% of the ground ivy leaf tissue. The seven herbicide treatments were 2,4-D ester at 3.2 kg ae/ha; metsulfuron at 0.02 kg/ha; aminocyclopyraclor at 0.08 kg ae/ha; 2,4-D + mecoprop + dicamba; triclopyr at 1.12 kg ae/ha, and the untreated check. The herbicide was mostly dry on the leaf surface when mowing 30 minutes following an application; however, the deck of the mower was cleaned with a blower to remove debris after each plot was mown to reduce the potential to track herbicide from one plot to another. Plots were treated with herbicide 29 October 2010. Herbicides were applied in 814 L/ha water with a CO2-pressurized sprayer at 207 kPa. Ground ivy coverage was visually rated. All data were analyzed using SAS (SAS Institute, Inc). The data were analyzed as a 3 X 5 Factorial without the untreated check. Means were separated using Fisher’s protected least significant difference when F tests were significant at α=0.05. When rated 17 November (3 weeks after application) there were no immediate visible effects of the herbicide treatments. However, on each spring rating date there was a significant effect of the herbicide. When rated on 8 July 2011, the 29 October 2010 application of aminocyclopyrachlor reduced ground ivy coverage most. The excellent control of ground ivy from aminocyclopyrachlor was consistent with other research done at this location. At no point in the experiment did the main effect of mowing have a significant impact on ground ivy coverage nor was there a significant mowing by herbicide interaction. Thus, this preliminary data suggests that whether or not turf is mown before or after an application may not be as important as previously thought for controlling broadleaf weeds. This experiment will be repeated in 2011-2012.