CGA-362622: Soil Behavior and Foliar Versus Root Absorption by Torpedograss (Panicum repens)¹

Abstract

Selective placement studies were conducted under greenhouse conditions to determine the relative importance of root vs. foliar absorption of postemergence-applied CGA-362622 by torpedograss. All application methods were equally effective in reducing torpedograss foliage as measured 4 wk after treatment. However, foliar + soil and soil-only were more effective than foliar-only in suppressing regrowth at 10 wk after treatment. Foliar absorption by torpedograss and subsequent translocation was determined with radiotracer techniques. After 72 h, 29% of the applied CGA-362622 had been absorbed, and 2 and 7% of the amount applied had accumulated in developing rhizomes and roots, respectively. CGA-362622 was more readily absorbed and translocated by the root. Hydroponically grown plants were transferred to a hydroponic solution spiked with CGA-362622 at 200 ppb. After 6 h, whole plant concentration was 113.1 ng/plant. Only 56% of amount absorbed remained in the roots, the remainder having been translocated to other tissues. The youngest leaf and the immature rhizomes accumulated 2 and 15%, respectively. CGA-362622 soil adsorption was slightly influenced by CGA-362622 concentration and greatly influenced by soil pH. Average percent recovered in the soil solution (i.e., not absorbed) was 15.3 and 27.4% at pH 5.7 and 6.7, respectively. Soil mobility was also pH dependent. Soil solution and soil mobility data support the observation that soil application followed by root entry is more effective in delivering phytotoxic concentrations to the regenerative tissues of torpedograss than foliar application.

Foliar and Root Absorption and Translocation of Bispyribac-sodium in Cool-season Turfgrass

“…Injury from soil or foliar plus soil treatments was approximately 82% at 28 DAT, whereas injury from foliar-alone treatments was 55%. As previously mentioned, similar research with other postemergence ALS-inhibiting herbicides such as rimsulfuron, trifloxysulfuron, and halosulfuron has shown that their activity on various species can be reduced when applied only to foliage versus to foliage and soil (McElroy et al 2004;Wehtje and Walker 2002;Williams et al 2003).…”

“…Herbicide Placement. Greenhouse studies were conducted to investigate the effect of selective placement of bispyribac on three cool-season turfgrass species using methods similar to those described by other researchers (McElroy et al 2004;Williams et al 2003). Soil medium was a 1:3 v/v ratio of sand and Holmdel sandy-loam soil (fine-loamy, mixed, active, mesic Aquic Hapludult) with a pH of 6.5 and organic matter content of 2%.…”

“…Wehtje and Walker (2002) reported that foliar plus soil applications of rimsulfuron at 53 g ai/ha provided more effective control of annual bluegrass than foliar-alone applications. Williams et al (2003) found that foliar plus soil or soil-alone applications of trifloxysulfuron suppressed regrowth of torpedograss (Panicum repens L.) at 10 wk after treatment (WAT) more effectively than foliar-alone applications. Foliar plus soil applications of trifloxysulfuron or halosulfuron reduced shoot number and weight of two Kyllinga species 60 DAT more effectively than foliar-alone applications (McElroy et al 2004).…”

Yellow Nutsedge (Cyperus esculentus) and Large Crabgrass (Digitaria sanguinalis) Response to Soil- and Foliar-Applied Mesotrione

“…Soil-plus-foliar treatments were not irrigated into the soil until 7 DAT because of the potential for herbicide leaching. Although we acknowledge these potential aberrations, we reference several publications on which we developed our methodology (McElroy et al 2003(McElroy et al , 2004Wilcut 1998;Williams et al 2003).…”

Cotton Response to CGA-362622 Applied Alone and in Combination with Selected Insecticides

“…Corkern et al (1999) reported greater cotton injury when pyrithiobac was applied to cotton receiving irrigation just before application compared with nonirrigated cotton. Williams et al (2003) suggested that CGA-362622 was phytotoxic to torpedograss (Panicum repens L.) and was attributed more to root entry of the herbicide than from foliar uptake. Applying malathion in mixture with either pyrithiobac or CGA-362622 increased injury from 12 to 26% 4 DAT compared with injury when herbicides were applied alone (Tables 1 and 2).…”