Increased yield potential associated with full‐season cotton (Gossypium hirsutum L.) varieties can be offset by excessive vegetative growth that leads to undesirable fruit shed and boll rot. Producers often make multiple mepiquat chloride (1,1‐dimethyl‐piperidinium chloride) applications with excessive seasonal use rates to combat this problem, often with inconsistent results. Field studies were conducted in 2004 and 2005 to evaluate reduced plant populations as a potential management tool to be used in conjunction with mepiquat chloride application strategies for managing plant height. Plant populations of 152883, 101929, and 50958 plants ha−1 received a single application at 12 nodes (15.2 g a.i. ha−1) or early bloom (45.8 g a.i. ha−1), sequential applications at 12 nodes (15.2 g a.i. ha−1) and early bloom (30.6 g a.i. ha−1), or the modified early bloom schedule (a plant growth regulator application decision aid that recommends rates and timing based on plant growth parameters). Mepiquat chloride application reduced final plant height at least 15 cm compared with the nontreated in both years but also reduced the number of main stem nodes in 2005. In 2005, lint yield was inversely related to plant population, and a significant yield response occurred with the modified early bloom mepiquat chloride application strategy. Mepiquat chloride application increased lint yield in 1 of 2 yr but was useful for reducing plant height regardless of population. Reducing plant population had no adverse effects on lint yield or fiber properties and may be valuable in achieving a desired plant stature with less intensive plant growth regulator management.

Cotton (Gossypium hirsutum L.) lint yield stability across a range of plant populations, coupled with expensive transgenic cotton seed, makes reduced seeding rates an attractive cost-saving option. Studies evaluated plant populations and seeding configurations in an effort to: (i) isolate a specific combination that minimizes seed use without sacrificing yield, and (ii) identify potential growth and development changes associated with cotton grown at these densities. Cotton planted in studies conducted during 2003 and 2004 on a Norwood silt loam (fine-silty, mixed, calcareous, thermic Typic Udifluvent) were hand thinned to densities ranging from 33 978 to 152 833 plants ha 21 in both hill-drop and drill-seeded configurations (96.5-cm row widths). Plant height, main-stem nodes per plant, maturity, boll retention by position, lint yield, and fiber quality were all evaluated. No seeding configuration 3 plant population interaction occurred for variables other than yield. A positive relationship existed between plant population and plant height; however, main-stem nodes per plant, days after planting to peak bloom, and boll retention were inversely related to plant density. Lint yield was highest for 152 883 plants ha 21 (1465 kg ha 21 ) planted in a hill-drop configuration with three plants per 20-cm hill spacing, and was not reduced until population was lowered to 33 975 (30.5-cm plant spacing, 1263 kg ha 21 ) and 50 958 (three plants per hill, 60-cm hill spacing, 1177 kg ha 21 ) plants ha 21 . Treatments did not influence fiber properties. Reduced seeding rates appear to be a viable cost-saving option, given that a uniform stand is achieved and appropriate management practices employed.

Field studies were conducted to evaluate red morningglory control with 2,4-D alone and in combination with dicamba, along with other postemergence herbicides applied both over the top and as directed treatments. For red morningglory 30 and 60 cm in height, complete control 14 or 21 d after treatment (DAT) was obtained during 2 yr with 2,4-D at 0.53 kg ai/ha, 2,4-D at 0.4 kg/ ha or more plus dicamba, atrazine at 2.23 kg ai/ha, flumioxazin at 0.10 kg ai/ha, and sulfentrazone at 0.35 kg ai/ha. When red morningglory were 1.8 m, weed control with most herbicides was less consistent than when applied to smaller plants. Red morningglory (1.8 m) was controlled 100% 28 DAT the first year with 2,4-D at 1.06 kg/ha and 78% the second year. In the first year, the 2,4-D plus dicamba prepackaged mixture at 0.8 + 0.28 kg ai/ha or 2,4-D plus the 2,4-D/dicamba prepackaged mixture (0.53 + 0.2/0.07, 0.53 + 0.4/0.14, or 0.79 + 0.1/0.04 kg/ha) provided control equal to that by 2,4-D alone at 1.06 kg/ha. In the second year, when herbicides were applied 3 wk earlier than the previous year and when weed growth was more vigorous, the 2,4-D plus the 2,4-D/dicamba prepackaged mixture at 0.79 + 0.1/0.04 kg/ha provided control equal to that by 2,4-D alone at 1.06 kg/ha but was the only 2,4-D plus dicamba treatment to control red morningglory equal to that by 2,4-D at 1.59 kg/ha (87%). Directed applications to the lower 45 cm of 1.8-m red morningglory plants with atrazine at 4.47 kg/ha and sulfentrazone at 0.35 kg/ha controlled weeds at least 96% 28 DAT in 2001, but control was 23 and 30 percentage points less, respectively, the second year.

Field studies conducted for two growing seasons evaluated the effect of 2,4-D applied at 1.6 kg ai/ha to ‘LCP 85-384’ sugarcane 7, 5, 3, and 1 wk before planting (WBP). Sugarcane was planted in mid September using both whole stalks and billet (45 cm) stem sections. When 2,4-D was applied 5 wk or closer to planting, sugarcane shoot emergence and population averaged across planting methods and years were reduced up to 28 wk after planting (WAP) relative to the nontreated control. By 52 WAP, sugarcane had compensated and stalk population was equivalent among treatments. Sugarcane height in response to 2,4-D varied between years, and only in 2001 at 52 WAP was a height reduction observed when 2,4-D was applied 1, 3, or 5 WBP. Crop injury in 2001 was further reflected in reduced sugarcane yield (at least 11%) and sugar yield (at least 12%) more than 1 yr after 2,4-D had been applied 5 wk or closer to harvest of sugarcane for seed. Sugarcane and sugar yields were equivalent for the nontreated control and the 7 WBP 2,4-D treatment in 2001, but 2,4-D application in 2002 did not negatively affect yield. Even though sugarcane shoot populations across the growing seasons were consistently higher for the billet planting system, yields averaged across 2,4-D application timings were greater for billets (18%) compared with whole stalks only for the first year. Because 2,4-D can have a residual effect on sugarcane yield more than 1 yr after the initial foliar application, a 7-wk period should be allowed between herbicide application and harvest of LCP 85-384 for billet or whole-stalk planting.

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