W. David Smith

Absorption, translocation, and metabolism of foliar-applied CGA-362622 in purple and yellow nutsedge (Cyperus rotundus and C. esculentus)

Abstract Studies were conducted to evaluate the absorption, translocation, and metabolism of 14C–CGA-362622 when foliar-applied to purple and yellow nutsedge. Less than 53% of the herbicide was absorbed after 96 h. Both nutsedge species translocated appreciable amounts of herbicide (30%) out of treated leaves. Translocation was both acropetal and basipetal, with at least 25% transported basipetally. Neither nutsedge species translocated more than 4% of applied radioactivity to the tubers and roots. Most of the metabolites formed by the nutsedge species were more polar than 14C–CGA-362622 and averaged 69 and 61% of the radioactivity in purple and yellow nutsedge, respectively. The half-life of CGA-362622 was estimated at 4 h in both purple and yellow nutsedge. Nomenclature: CGA-362622, N-([4,6-dimethoxy-2-pyrimidinyl]carbamoyl)-3-(2,2,2,-trifluoroethoxy)-pyridin-2-sulfonamide sodium salt; purple nutsedge, Cyperus rotundus L. CYPRO; yellow nutsedge, Cyperus esculentus L. CYPES.

Clomazone, Fomesafen, and Bromoxynil Systems for Bromoxynil-Resistant Cotton (Gossypium hirsutum)1

Abstract: Studies were conducted at Clayton, Lewiston, and Rocky Mount, NC, to evaluate weed and cotton response to herbicide systems in bromoxynil-resistant Stoneville BXN 47 cotton. Herbicide systems that included clomazone preemergence (PRE) controlled broadleaf signalgrass, common lambsquarters, common ragweed, goosegrass, large crabgrass, and prickly sida greater than 88%. Inconsistent Palmer amaranth control was observed with the addition of fomesafen PRE to clomazone PRE and pendimethalin preplant-incorporated (PPI) herbicide systems. Addition of bromoxynil early postemergence (EPOST) to clomazone and pendimethalin systems increased ivyleaf morningglory control to greater than 84% and provided higher yields than did the same systems without bromoxynil. Bromoxynil EPOST followed by (fb) cyanazine + MSMA late postemergence directed (LAYBY) improved weed control in clomazone and pendimethalin systems. Clomazone PRE and pendimethalin PPI with or without fomesafen PRE fb bromoxynil EPOST fb LAYBY herbicides controlled weeds and yielded equivalent to the standard herbicide system of pendimethalin PPI fb fluometuron PRE fb bromoxynil EPOST fb LAYBY. Nomenclature: Bromoxynil; clomazone; cyanazine; fluometuron; fomesafen; MSMA; pendimethalin; broadleaf signalgrass, Brachiaria platyphylla (Griseb) Nash. #3 BRAPP; common lambsquarters, Chenopodium album L. # CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; goosegrass, Eleusine indica (L.) Gaertn. # ELEIN; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. # IPOHE; large crabgrass, Digitaria sanguinalis L. # DIGSA; Palmer amaranth, Amaranthus palmeri S. Wats. # AMAPA; prickly sida, Sida spinosa L. # SIDSP; cotton, Gossypium hirsutum L. ‘Stoneville BXN 47’. Additional index words: Herbicide-tolerant crops. Abbreviations: EPOST, early postemergence; fb, followed by; LAYBY, late postemergence directed; PD, postemergence directed; POST, postemergence; PPI, preplant incorporated; PRE, preemergence.

Weed Management Systems in Glyphosate-Resistant Cotton1

Studies were conducted at Clayton, Lewiston-Woodville, and Rocky Mount, NC, to evaluate weed and cotton response to herbicide systems in glyphosate-resistant cotton in 1995 and 1997. Herbicide systems evaluated included various combinations of soil-applied (trifluralin and fluometuron) and postemergence (POST) (glyphosate or pyrithiobac) herbicides with or without late postemergence-directed (LAYBY) treatments of cyanazine plus MSMA. Glyphosate-resistant cotton injury was less than 5% with all herbicide treatments. Glyphosate POST systems were as efficacious in weed control as other herbicide systems. Depending on location, glyphosate and pyrithiobac POST systems usually required cyanazine plus MSMA LAYBY for season-long control of common lambsquarters, goosegrass, large crabgrass, pitted morningglory, prickly sida, and Texas panicum. Glyphosate POST applied as needed provided weed control equivalent to soil-applied plus POST herbicides, although lint yield was slightly reduced depending on location. Herbicide systems that included soil-applied herbicides required one to two treatments of glyphosate POST and post-directed for season-long weed control and high cotton lint yields, whereas the same herbicide systems without soil-applied herbicides required two to three glyphosate treatments. In all herbicide systems, a residual soil-applied or LAYBY herbicide treatment increased yield compared with glyphosate POST only systems. Location influenced weed control and cotton yield. Generally, as herbicide inputs increased, yield increased. Nomenclature: Cyanazine; fluometuron; glyphosate; MSMA; pyrithiobac; trifluralin; common lambsquarters, Chenopodium album L. #3 CHEAL; goosegrass, Eleusine indica (L.) Gaertn. # ELEIN; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; Texas panicum, Panicum texanum Buckl. # PANTE; cotton, Gossypium hirsutum L. ‘Paymaster 1330RR’. Additional index words: CHEAL, DIGSA, ELEIN, herbicide-resistant crops, IPOLA, PANTE, SIDSP. Abbreviations: ANS, as needed spray; fb, followed by; LAYBY, late postemergence-directed; PDS, post-directed; POST, postemergence; PPI, preplant incorporated; PRE, preemergence.

Yield and Physiological Response of Flue-Cured Tobacco to Simulated Glyphosate Drift

Field trials were conducted in 2001 at the Tobacco Research Station near Oxford, NC, and in 2002 at the Lower Coastal Plains Research Station near Kinston, NC, to determine tobacco yield, injury, and shikimic acid accumulation in response to simulated glyphosate drift. Glyphosate was applied to 12- to 13-cm-high tobacco ‘K326’ early postemergence at 0, 9, 18, 35, 70, 140, 280, 560, and 1,120 (1×) g ai/ha. Crop injury was rated 7 and 35 d after treatment (DAT) and shikimic acid accumulation in leaves at 7 DAT, tobacco yield, and leaf grade index (whole-plant index of harvest interval leaf value) were also assessed. Shikimic acid accumulation and injury symptoms increased similarly as glyphosate rate increased. Glyphosate rates of 140 g/ha (0.125 of recommended rate) or higher resulted in significant crop injury, reduced tobacco yield, and decreased leaf grade index. Shikimic acid accumulation at 7 DAT was inversely related to tobacco yield. Shikimic acid accumulation was found to be an effective diagnostic tool to determine glyphosate drift in tobacco; however, in-season data are needed to correlate shikimic acid accumulation with yield loss. Nomenclature: Glyphosate; tobacco, Nicotiana tabacum L. ‘K326’. Additional index words: Crop injury, herbicide assay, shikimate. Abbreviation: DAT, days after treatment.

Purple and Yellow Nutsedge (Cyperus rotundus and C. esculentus) Response to Postemergence Herbicides in Cotton

Abstract Greenhouse studies were conducted to evaluate the nature of the cotton postemergence (POST) herbicides followed by (fb) MSMA postemergence-directed (LAYBY) for foliar and tuber reduction of yellow and purple nutsedge when applied to nutsedge at two different application timings. Trifloxysulfuron at 4 and 6 g ai/ha fb MSMA LAYBY reduced 10- to 15- and 20- to 30-cm purple and yellow nutsedge root and shoot dry weights by at least 56%. However, the effect of weed size at the time of application was significant for trifloxysulfuron at 6 g/ha for percent root and shoot reductions in yellow nutsedge and percent root reduction in purple nutsedge. Significance of herbicide rate was only observed for percent shoot and root reduction of 10- to 15-cm yellow nutsedge. Trifloxysulfuron treatments reduced purple and yellow nutsedge shoot and root dry weights equivalent to treatments involving glyphosate POST fb MSMA LAYBY. MSMA at 1,120 and 2,240 g/ha and glufosinate POST fb MSMA LAYBY were effective for reducing purple and yellow nutsedge shoot dry weights, although percent reduction was influenced by nutsedge height at herbicide application. Treatments involving pyrithiobac POST fb MSMA LAYBY slightly increased 10- to 15-cm yellow nutsedge root dry weights. MSMA at either rate produced additive responses when included in tank mixtures with trifloxysulfuron at either rate or pyrithiobac POST fb MSMA LAYBY in yellow nutsedge. Other tank mixes or sequential combinations did not cause additive or synergistic responses. Nomenclature: Glufosinate; glyphosate; MSMA; pyrithiobac; trifloxysulfuron; purple nutsedge, Cyperus rotundus L. CYPRO; yellow nutsedge, Cyperus esculentus L. CYPES;cotton, Gossypium hirsutum L

Uptake, translocation, and metabolism of sulfentrazone in peanut, prickly sida (Sida spinosa), and pitted morningglory (Ipomoea lacunosa)

Abstract Studies were conducted to evaluate uptake, translocation, and metabolism of root-absorbed 14C-sulfentrazone in peanut, prickly sida, and pitted morningglory. Peanut absorbed more than five and three times greater 14C-sulfentrazone than pitted morningglory and prickly sida, respectively. All plant species translocated appreciable amounts (≥ 39%) of radioactivity to the leaves. The three plant species had some capacity to metabolize 14C-sulfentrazone. At 3 h after treatment, 7, 29, and 71% of the radioactivity in the shoots of peanut, prickly sida, and pitted morningglory, respectively, was sulfentrazone. Sulfentrazone levels in the shoots at 3 and 6 h after treatment correspond to reported tolerance levels, with peanut being the most tolerant of the three species, whereas prickly sida and pitted morningglory are moderately tolerant and completely susceptible to sulfentrazone, respectively. Levels of metabolites varied among species, plant part, and harvest timing. On the basis of these data, tolerance in peanut is largely due to its ability to rapidly metabolize sulfentrazone. Nomenclature: Sulfentrazone; pitted morningglory, Ipomoea lacunosa L. IPOLA; prickly sida, Sida spinosa L. SIDSP; peanut, Arachis hypogaea L. ARAHY ‘NC 12C’.

Tobacco Response to Residual and In-Season Treatments of CGA-3626221

Experiments were conducted to determine tobacco tolerance to CGA-362622 applied pretransplant (PRE-T) and postemergence (POST) to tobacco and applied the previous year preemergence (PRE) and POST to cotton. CGA-362622 applied at 3.75 or 7.5 g ai/ha PRE-T injured ‘K326’ flue-cured tobacco 1%, whereas POST treatments resulted in 4 to 5% injury. Tobacco injury was transient with no mid- or late-season injury noted. Tobacco yields from all CGA-362622 POST treatments were not different from the nontreated weed-free check. Tobacco treated with 7.5 g/ha CGA-362622 PRE-T yielded greater than nontreated weed-free tobacco or tobacco treated with CGA-362622 POST. When grown in rotation, tobacco was not injured, and yields were not influenced by CGA-362622 applied PRE or POST to cotton the previous year. Nomenclature: CGA-362622; cotton, Gossypium hirsutum L.; tobacco, Nicotiana tabacum L. Additional index words: Carryover, crop injury, sulfonylurea herbicide. Abbreviations: ALS, acetolactate synthase; LAYBY, late POST-directed; POST, postemergence; PPI, preplant incorporated; PRE, preemergence; PRE-T, pretransplant.

EFFECTS OF STAND LOSS, PLANTING DATE, AND REPLANTING METHOD ON YIELD AND QUALITY OF FLUE-CURED TOBACCO

Abstract Research was conducted at one location in 2003 and two locations in 2004 and 2005 to evaluate the effects of stand loss, planting date, and replanting method on flue-cured tobacco yield and quality. Stand loss treatments included a 10%, 20%, 30%, and 40% stand loss at two and four weeks after transplanting (WAT). In recent years, early season infections by Tomato spotted wilt virus (TSWV) have caused significant stand losses in North Carolina, so an additional treatment was included to simulate the effects of plant loss to tomato spotted wilt. Simulated losses consisted of a 10%, 10%, and 20% stand loss at 3, 4, and 5 weeks after transplanting, respectively. Planting date treatments included planting at the normal transplanting date and at 2, 3, 4, and 5 weeks after the normal transplanting date. To evaluate the effects of replanting method, tobacco was replanted at 2 or 4 weeks after normal replanting on an existing row ridge, a rebedded row ridge, and a tilled and rebedded row ridge. Due to exc...

Uptake, Translocation, and Metabolism of Root Absorbed Sulfentrazone and Sulfentrazone plus Clomazone in Flue-Cured Tobacco Transplants1

Research was conducted to evaluate root uptake, translocation, and metabolism of 14C-sulfentrazone alone or in a mixture with clomazone in solution in flue-cured tobacco transplants. Uptake and translocation of sulfentrazone was rapid and was not affected by the addition of clomazone. Fifty-nine and 65% of the 14C absorbed by the plant was translocated to the leaves within 24 h with sulfentrazone alone and in the clomazone plus sulfentrazone mixture, respectively. Differences in plant metabolism were observed between sulfentrazone alone and sulfentrazone plus clomazone. After 3 h, 66% of the 14C recovered from the leaves was metabolized when sulfentrazone was applied alone, compared to 91% when sulfentrazone was applied with clomazone. The difference could indicate that metabolism of sulfentrazone by tobacco transplants was enhanced by the presence of clomazone. Nomenclature: Clomazone, sulfentrazone, flue-cured tobacco, Nicotiana tabacum L. ‘NC 71’. Additional index words: Enhanced metabolism, safening, tolerance. Abbreviations: HAT, hours after treatment; LSS, liquid scintillation spectrometry; PPI, preplant incorporated treatment; PRE-T, pre-emergence soil surface treatment.

TOBACCO (NICOTIANA TABACUM) TOLERANCE TO PRE-TRANSPLANT AND POSTEMERGENCE APPLICATIONS OF DICLOSULAM

Abstract Field studies were conducted at Oxford, NC in 1997 and 1998 to evaluate tolerance of tobacco to pre-transplant (PRE-T) and postemergence (POST) applications of diclosulam. Tobacco injury w...