Charcoal root dip and controlled release carrier effects on hexazinone selectivity with sycamore (Platanus occidentalis) seedlings

Hexazinone, premixed with controlled release carriers, was applied to charcoal root-dipped, sycamore seedlings in field studies conducted in 1997 and 1998. The objective was to determine the combined effects of the carriers and root dips on herbaceous weed control and seedling growth and survival. Two controlled release carriers, methylated seed oil and recycled newspaper fluff, were compared with the standard water carrier. The root dip consisted of activated charcoal combined with a synthetic water thickener. Weed control using the oil and newspaper carriers was less than or equal to weed control using the standard water carrier. Weed control increased with increasing hexazinone rate. Groundline diameter growth for root-dipped seedlings increased by four-fold in 1997, but had both negative and positive results in 1998. Survival for root-dipped seedlings increased by three-fold in 1997, but had mixed results in 1998, depending on the carrier. Accidental uptake of herbicides by sycamore foliage after bud break in 1998 may have lead to the inconsistent seedling responses to charcoal root dips.