Controlling Weeds in Newly Planted Ground Covers with Herbicide - Mulch Combinations Using Activated Carbon as a Detoxifying Agent

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University of Delaware
This study was initiated to determine the best chemical weed control method for us in establishing new plantings of ground covers. Varying levels of herbicides, different mulches, and activated carbon as a protectant were tested at Newark, Delaware during 1969 and 1970. The experimental design was a split plot, and was replicated three times. The ground cover plants studied were Aiuga reptans, Hedera helix, Pachysandra terminalis, and Vinca minor. Herbicides studied were simazine (4 lbs./A), dichlobenil (6 lbs./A), diphenamid (6 lbs./A), simazine (2 lbs./A) combined with diphenamid (4 lbs./A), and dichlobenil (4 lbs./A) combined with diphenamid (4 lbs./A). Mulches studied were licorice root (on-inch depth) and “FoliCote” (diluted in ater at a ratio of one to five). On half of all plant material was root-dipped in activated carbon. Herbicide toxicity to the ground cover was rated by a standard visual evaluation on a scale from one to five. Weed infestation was determined as stand (number of plants) and vigor (dry weight in grams). Growth of ground cover plants was measured by using a grid, and the percentage of ground covered by the plants within this grid was estimated. The stand (number of plants) and the vigor (fresh weight in grams) of the ground cover plants was also determined. With no mulch, weed control studies indicated that dry weight production of Panicum dichotomiflorum (fall panicum) was significantly reduced by the simazine-diphenamid and the dichlobenil-diphenamid herbiced treatments. Also with no mulch, the stand and vigor of Portulaca oleracea (purslane) was significantly reduced by simazine (4 lbs./A), diphenamid (6 lbs./A), and the simazine-diphenamid combination. The no mulch-herbicide treatments were not effective in controlling Eragrostis cilianesis (stinkgrass) and Amaranthus retroflexus (redroot pigweed). However, studies indicated that weed control of all weed species was significantly improved when licorice root mulch was applied to a one-inch depth over all herbicide treatments. Herbicide injury studies indicated that activated carbon did detoxify all herbicides tested. Plants root-dipped in activated carbon showed less herbicide injury, greater fresh weight, and more growth (percentage of ground covered) than those plants that were not so treated.
Weed control, Horticulture, Herbicides, Mulch, Groundcovers