Field studies were conducted in 2002 and 2003 to determine the effects of herbicides applied below suggested use rates on weed management, yield, and estimated net return of peanut in both narrow and wide row-spacing regimes. In the single row-spacing regime study, diclosulam at 6 g/ha (1/4×) (1/4 labeled use rate) plus flumioxazin at 26 g/ha (1/4×) applied PRE followed by (fb) imazapic POST at 17, (1/4×), 35, (1/2×), or 70, (1×) g/ha was the lowest herbicide input that provided at least 80% control of sicklepod, yellow nutsedge, Florida beggarweed, and hairy indigo at 21 d after treatment (DAT). By 42 DAT, weed control was ≥ 80%, similar to herbicide treatments applied at labeled rates. In the twin row-spacing regime study at Jay, FL, and Citra, FL, in 2003, yellow nutsedge control was lowest (83 to 85%) from diclosulam applied at 1/4× in combination with flumioxazin at 1/4× PRE and flumioxazin at 1/4× or 52 g/ha (1/2×) PRE alone. All other herbicide treatments provided > 90% control. Diclosulam at 13 g/ha (1/2×) fb imazapic at 1/2× and flumioxazin at 1/4× fb imazapic at 1/2× was the lowest rate combination that provided > 80% control of sicklepod. Florida beggarweed control was > 90% with all rate combinations except diclosulam PRE alone, diclosulam at 1/4× PRE fb imazapic at 1/4× POST, and imazapic at 1/4× alone POST. Net return in the single-row spacing regime was highest for flumioxazin at 105 g/ha (1×) PRE alone, diclosulam at 1/4× applied with flumioxazin at 1/4× PRE alone or fb imazapic at 1× ($1,114, $1,094, and $990/ha, respectively). The twin row-spacing regime net return was highest with diclosulam PRE alone at 1/4, 1/2, or 26 g/ha (1×) ($2,063, $1,846, $1,734/ha, respectively). Diclosulam applied with flumioxazin at 1/2× fb imazapic at 1/2× was the lowest herbicide tank-mix input providing high net return at $1,162/ha.

Laboratory studies were conducted in 2006 and 2007 to evaluate the effects of temperature and propanil on alligatorweed control with penoxsulam. Biomass reduction of alligatorweed at 42 d after treatment (DAT) compared to nontreated was greatest at 21/11 C (day/night) compared to 26/18 C or 30/25 C for all treatments. Propanil plus penoxsulam reduced biomass less than penoxsulam applied alone, independent of temperature. At 21 and 27 C, delaying propanil application 3 d after penoxsulam provided similar biomass reduction to penoxsulam applied alone. At 27 C and 30 C, delaying propanil application 10 d after treatment was required to achieve biomass reduction greater or equal to penoxsulam applied alone. Absorption and translocation of 14C penoxsulam indicated that propanil reduced absorption of penoxsulam into the treated leaf of alligatorweed 48 h after treatment. This research demonstrates the potential for propanil to antagonize penoxsulam when applied to alligatorweed. Under the most severe antagonistic conditions (30 C) propanil applications following penoxsulam needed to be delayed 10 d to avoid antagonism.

Studies were conducted in 2003 and 2004 over seven environments evaluating rice root growth inhibition (RGI) and foliar injury from penoxsulam at 30 and 60 g ai/ha and bispyribac-sodium at 30 g ai/ha applied to four- to five-leaf rice at three flood timings, 1, 7, and 14 d after herbicide treatment (DAT), for five rice cultivars, ‘Bengal’, ‘Cypress’, ‘Wells’, ‘Cocodrie’, and ‘XP712’. Flooding at 1 and 7 DAT resulted in greater RGI compared with flood at 14 DAT when evaluated 1 wk after flood (WAF). By 2 WAF, RGI was greater with flooding at 1 DAT compared with flooding at 7 DAT for cultivars Bengal, Cypress, and Wells. Analyzing flood timing 1 DAT, bispyribac-sodium reduced root growth of Bengal and Cypress compared with penoxsulam at 30 g/ha at 1 week after treatment (WAT). At 2 WAT, RGI for Cocodrie was higher following penoxsulam at 60 g/ha when compared with bispyribac-sodium. By 3 WAT, RGI was higher following penoxsulam at 60 g/ha when compared with penoxsulam at 30 g/ha for Cocodrie and greater than bispyribac-sodium and penoxsulam at 30 g/ha for Cypress. Foliar injury following penoxsulam at both rates was less than injury following bispyribac-sodium for all cultivars except XP712 at 1 WAT. XP712 resulted in < 5% RGI and < 6% foliar injury at each evaluation. Rice grain yield was not affected by herbicide treatment for any cultivar compared with the standard treatment of propanil plus quinclorac.

Clomazone was labeled for rice in 2001; however, that label excluded its use on coarse- (light) textured soils, including sand, loamy sand, and sandy loam with less than 1% organic matter due to rice injury. Field studies conducted in 2005, 2006, and 2007 evaluated weed control and tolerance of rice to early postemergence (EPOST) applications of clomazone alone and tank mixed with other herbicides on sandy loam and clay loam soils. At 42 d after treatment (DAT), broadleaf signalgrass (BRAPP) and barnyardgrass (ECHCG) control was > 86%. At 14 DAT, rice injury was greatest (13%) from clomazone applied preemergence (PRE) at 0.44 kg ai/ha on sandy soil. Annual sedge (CYPCP) control was > 78% on sandy loam soils at 14 DAT, but increased to > 90% by 42 DAT. On clay loam soils, CYPCP control at 42 DAT ranged from 60 to 76% from clomazone alone or tank mixed with cyhalofop or fenoxaprop. All other tank mixes provided > 80% control. Hemp sesbania (SEBEX) control was > 80% from all tank mixes. Clomazone alone provided < 77% control. Data suggest that clomazone can be used EPOST in combination with other herbicides without causing significant rice injury on sandy loam soils in Texas.

Alligatorweed is a perennial, invasive weed in southern United States rice production, but knowledge on effective management of this weed is limited, especially in conventional (non-imidazolinone-resistant) rice fields. Field studies were conducted in multiple environments in southeastern Texas to evaluate different herbicide options involving penoxsulam, propanil, triclopyr, halosulfuron, bispyribac-sodium, bensulfuron, and quinclorac for alligatorweed control in conventional drill-seeded rice when applied at early POST (EPOST), late POST (LPOST), or both. Among the herbicide options evaluated, penoxsulam alone (up to 83%), penoxsulam plus triclopyr (up to 87%), or bispyribac-sodium plus triclopyr (92%) provided superior alligatorweed control. Plots treated with penoxsulam plus triclopyr EPOST produced the highest yields (9,550 kg ha−1), which were comparable to plots receiving penoxsulam plus triclopyr LPOST (9,320 kg ha−1), penoxsulam alone EPOST (9,280 kg ha−1), and penoxsulam plus halosulfuron LPOST (9,180 kg ha−1). Considering both weed control and rice grain yields, penoxsulam plus triclopyr applied EPOST was found to be the best option among the treatments tested. The treatments bensulfuron alone, bensulfuron plus propanil, penoxsulam plus propanil, triclopyr plus propanil, and bispyribac-sodium plus propanil provided poor (≤ 65%) alligatorweed control. Results also suggest the likelihood for antagonistic interactions when tank-mix combinations tested in this study included propanil.