Field experiments were conducted to determine suitable application timings and rates of MON 37500 for downy brome control in winter wheat. MON 37500 applied preemergence (PRE) or in fall postemergence (POST) provided better control of downy brome than when applied spring POST. MON 37500 at rates ranging from 19 to 33 g ai/ha applied PRE or fall POST controlled downy brome >85%. MON 37500 applied spring POST at 60 g/ha only suppressed growth of downy brome. Winter wheat was not visibly injured and maturity was not delayed by MON 37500 applied up to 60 g/ha at any of the application timings. Winter wheat yield responded positively to all MON 37500 treatments but PRE or fall POST applications usually resulted in greater yields than spring POST applications. Wheat yields progressively increased with increasing rates of MON 37500 up to 30–40 g/ha, above which yields tended to plateau or, in two instances, decline slightly. MON 37500 is an important new herbicide that should enable growers to better manage downy brome in winter wheat production systems.

Carryover potential of imazaquin (0.14 kg ai ha−1), chlorimuron plus metribuzin (0.06 + 0.36 kg ha−1), and fomesafen (0.28 kg ha−1) to snap bean, watermelon, cucumber, mustard, and sunflower was evaluated in Arkansas in 1987 to 1989. Crops were direct-seeded into treated plots at various times after application. Imazaquin and chlorimuron plus metribuzin injured sunflower, watermelon, cucumber, and mustard when planted 16 wk following application in one of two years. Fomesafen injured all crops initially but did not injure snap bean, sunflower, watermelon, and cucumber planted 16 wk after application. In experiments in which herbicides were applied to soybean, fall-planted spinach and mustard were injured in one of two years.

The influence of hot-dry and cool-moist environments on primisulfuron efficacy on giant foxtail and quackgrass was compared at the University of Wisconsin Biotron. Primisulfuron was applied POST at 20 and 40 g ai ha-1 with nonionic surfactant (NIS) or crop oil concentrate (COC) and with or without 28% nitrogen fertilizer (28% N). Giant foxtail control 3 wk after treatment was not affected by primisulfuron rates or adjuvants. Adding 28% N tended to improve quackgrass control with primisulfuron plus NIS or COC. Primisulfuron was more injurious to both giant foxtail and quackgrass in the cool-moist than the hot-dry environment. Absorption of 14C-primisulfuron into giant foxtail tissue 3 days after treatment (DAT) was greater in the cool-moist than the hot-dry environment Translocation of 14C out of treated leaf of quackgrass 3 DAT was greater in the cool-moist than the hot-dry environment. More 14C was absorbed and translocated in giant foxtail than quackgrass. Absorbed 14C was translocated equally to underground and above treated leaf sections of quackgrass, whereas more 14C was translocated above the treated leaf of giant foxtail.

Experiments were conducted in weed-free environments to determine corn tolerance to trifloxysulfuron applied PRE or POST, and to determine the potential for trifloxysulfuron applied PRE or POST to cotton to injure corn grown in rotation the following year. Trifloxysulfuron at 3.75, 7.5, or 15 g ai/ha applied PRE or POST resulted in 98% stand reduction of imidazolinone-tolerant (IT) corn and 100% stand reduction in conventional corn. No injury occurred to imidazolinone-resistant (IR) corn. A corn cultivar yield response was observed, with conventional nontreated corn yielding 8,850 kg/ha and greater than nontreated IT corn at 7,900 kg/ha. Nontreated IR corn yielded the least, at 6,400 kg/ha, and these yields were equivalent to trifloxysulfuron-treated IR corn at 6,590 kg/ha. Cotton treated with trifloxysulfuron PRE at any rate was injured less than 8%. Both trifloxysulfuron at 7.5 g/ha POST and pyrithiobac at 70 g ai/ha POST injured cotton 11% early in the season. Neither trifloxysulfuron nor pyrithiobac influenced weed-free cotton lint yields. When grown in rotation, corn was not injured by trifloxysulfuron or pyrithiobac applied the previous year to cotton, and yields were not influenced.

Experiments were conducted to determine peanut tolerance to CGA-362622 applied preemergence (PRE) and postemergence (POST) and to determine the potential for CGA-362622 applied PRE and POST to cotton to injure peanut grown in rotation the following year. CGA-362622 at 3.75 and 7.5 g ai/ha applied PRE visually injured peanut 11 and 16%, respectively, at 5 wk after treatment (WAT) but did not influence peanut yield. POST treatments at 3.75 and 7.5 g/ha injured peanut 63 and 93%, respectively, at 4 WAT and reduced peanut stand by 53 and 89% at 11 WAT, respectively. Peanut pod yield was reduced 73.1 and 97.9% by CGA-362622 POST at 3.75 and 7.5 g/ha, respectively, compared with the untreated weed-free control. CGA-362622 PRE at 3.75 and 7.5 g/ha reduced peanut pod yield 7.5 and 12.6%, respectively. Cotton was injured 9% or less by CGA-362622 PRE or POST at 3.75 or 7.5 g/ha and up to 25% with CGA-362622 POST at 15 g/ha. However, CGA-362622 did not influence weed-free cotton lint yields, regardless of method or rate of application. Peanuts grown in rotation were not injured, and yields were not influenced by CGA-362622 applied PRE or POST the previous year to cotton.

Experiments were conducted from 1998 to 2000 at Rocky Mount, NC, in weed-free environments to determine soybean tolerance to preplant (PP) applications of trifloxysulfuron and the potential for trifloxysulfuron applied preemergence (PRE) and postemergence (POST) to cotton to injure soybean grown in rotation the following year. Trifloxysulfuron at 3.75 and 7.5 g ai/ha applied PP 2 wk before seeding injured conventional soybean less than 5%, whereas no injury was observed when seeding was delayed 4 or 6 wk after PP treatment. No injury to sulfonylurea-resistant soybean (SR) was observed for any treatment. Soybean yields were not influenced by trifloxysulfuron treatment. Cotton injury was 7% or less with trifloxysulfuron applied PRE or POST at 3.75 and 7.5 g/ha. Trifloxysulfuron at 15 g/ha PRE or POST injured cotton a maximum of 14 to 18%. Trifloxysulfuron did not reduce cotton lint yields regardless of method or rate of application. Both conventional and SR soybean were not injured nor were yields influenced by trifloxysulfuron applied PRE or POST the previous year to cotton.

Field trials were conducted to evaluate imazosulfuron applied POST at 0.1, 0.2, 0.3, and 0.4 kg/ha to watermelon at the two- to four-leaf stage or to vines 30.5 cm long. At 7 d after treatment (DAT), crop injury to watermelon increased linearly for both growth stages as rate increased. The least injury to watermelon observed 7 DAT was 19 and 15%, respectively, for the two- to four-leaf and 30.5-cm growth stages treated with 0.01 kg/ha imazosulfuron. The 0.4 kg/ha imazosulfuron treatment caused the greatest watermelon injury (approximately 30%) at both application timings. Yield of watermelon treated with 0.1 and 0.2 kg/ha imazosulfuron applied at the two- to four-leaf and 30.5-cm stages were similar to the nontreated check (all plots were maintained weed-free). For both application timings, yield decreased linearly as imazosulfuron rate increased. The application of imazosulfuron to watermelon at the 30.5-cm stage averaged across rates resulted in less injury at 15 DAT (16%) and greater yield (92,869 kg/ha) than watermelon treated at two- to four-leaf stage averaged across rates (29%, 83,560 kg/ha). Internal fruit quality was not affected by imazosulfuron.

Studies were conducted in 1999, 2000, and 2001 to evaluate cotton response to CGA 362622 applied postemergence with various adjuvants. In field studies, CGA 362622 was applied at 3.8 or 7.5 g ai/ha with nonionic surfactant, crop-oil concentrate (COC), or a urea-based adjuvant. A nontreated control was maintained weed free for comparison. Crop injury over all years at 1 wk after treatment (WAT) was 27 and 34% from 3.8 and 7.5 g/ha CGA 362622, respectively, when rates were pooled over adjuvants. At 4 WAT, injury was 6 to 14% with 3.8 g/ha and 10 to 21% with 7.5 g/ha CGA 362622 during the 3-yr study. Cotton heights at 2 WAT were reduced by 16 to 31% of nontreated cotton heights by CGA 362622. Heights of treated cotton did not differ and were generally equivalent to the nontreated control at 8 WAT. Cotton injury and height reduction were greatest when CGA 362622 was applied with COC. Cotton lint yields and fiber quality were not affected by CGA 362622 rate or adjuvant treatment. Cotton injury from CGA 362622 in the greenhouse was similar to that in the field. Initial cotton injury and subsequent reduction in leaf area or shoot dry weight were generally lowest when CGA 362622 was applied with no adjuvant or UBA in the greenhouse.

Several field studies have observed increased foramsulfuron efficacy for the control of dallisgrass when foramsulfuron is applied after MSMA. Therefore, laboratory studies were conducted with mature dallisgrass to study the absorption and translocation of 14C-foramsulfuron, and then examine the impact of preliminary applications (preapplications) of MSMA or foramsulfuron on herbicide absorption and movement. Herbicide absorption increased rapidly through 4 h, and by 8 h, differences in absorption between pretreated and control plants were evident. After 48 h, foramsulfuron absorption in non-pretreated plants was 55%, whereas plants that received either pretreatment absorbed 70% of the herbicide. Translocation above (younger tissue) and below (older tissue) the treated leaf was 0.65 and 0.62% for non-pretreated plants, respectively. Pretreatment with foramsulfuron resulted in the translocation of 2.12 and 1.55% of applied radioactivity above and below the treated leaf, respectively. Pretreatment with MSMA resulted in the translocation of 2.33 and 2.34% of applied radioactivity above and below the treated leaf, respectively. These data indicated that pretreatment of mature dallisgrass with either foramsulfuron or MSMA results in an increase in both uptake and translocation of foramsulfuron applied 2 wk after pretreatment. The increase in absorption and translocation of foramsulfuron in the pre–MSMA-treated plants may explain the increase in control observed in the field when comparing it to the pre–foramsulfuron-treated dallisgrass plants.

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.

Cogongrass is an aggressive perennial weed, which causes severe yield losses in major crops of the moist savanna of West Africa. Field studies were conducted from 2000 to 2002 at Alabata and Ilorin, Nigeria, to evaluate the influence of dosage and time of nicosulfuron application on the control of cogongrass and corn grain yield. Nicosulfuron dosages were 50, 100, 150, and 200 g ai/ha applied 1, 2, 3, or 4 wk after planting (WAP) corn. Hand-weeded and nonweeded treatments were the controls. Three to 4 wk after treatment and at final harvest, all plots that received nicosulfuron had significantly lower cogongrass shoot dry matter (DM) than the nonweeded control across locations in all years (P ≤ 0.01). Nicosulfuron increased corn grain yield at Alabata by 96% in 2000, 100% in 2001, and 34 to 54% in 2002, and at Ilorin by 79 to 83% in 2001 and 60 to 69% in 2002 when compared with the nonweeded control. The weeded control had corn grain yield similar to plots that received nicosulfuron at 200 g/ha at Alabata in 2001, 150 g/ha at Ilorin in 2001, 50 to 200 g/ha at Alabata in 2002, and 150 and 200 g/ha at Ilorin in 2002. There were negative linear relationships between corn DM, grain yield, and cogongrass shoot DM. Application of nicosulfuron at 1 or 2 WAP, when cogongrass was 22 to 27 cm tall, gave better grain yield and lower cogongrass shoot DM than at 3 or 4 WAP, when cogongrass was 36 to 45 cm tall. The study concludes that 150 to 200 g/ha of nicosulfuron applied at 1 or 2 WAP is effective for cogongrass control without adverse effect on corn grain yield.

Sulfonylurea (SU)-resistant monochoria has recently been found in rice paddies in Korea. A quick and accurate means of confirming herbicide resistance is necessary to take timely management decisions. This article describes a rapid and reliable assay to detect SU-resistant biotype of monochoria. The techniques tested include seed germination, in vivo and in vitro acetolactate synthase (ALS; EC 4.1.3.18) activity, leaf, and whole-plant bioassays. In the whole-plant bioassay, shoot dry weight of the resistant (R) biotype was 3,200-fold less affected by imazosulfuron and sevenfold less affected by pyrazosulfuron-ethyl than the susceptible (S) biotype. Although the whole-plant bioassay is reliable, it is expensive, requires a lot of infrastructure, and takes a few months to complete. The germination rate of the R biotype in petri dish bioassays was > 200-fold less inhibited by imazosulfuron and 100-fold less inhibited by pyrazosulfuron-ethyl than that of the S biotype. Seed germination bioassays in petri dishes do not require as much infrastructure as whole-plant bioassays do and can be completed in a shorter time. Leaf bioassays showed that leaf color of the R biotype was > 1,600- and 300-fold less affected by imazosulfuron and pyrazosulfuron-ethyl, respectively, compared with that of the S biotype. This assay takes about 6 d to complete. In vivo ALS assays showed lower levels of resistance to ALS herbicides than did in vitro ALS assays, where the R biotype was about 200- and 30-fold less sensitive to imazosulfuron and pyrazosulfuron-ethyl, respectively, than the S biotype. All assays successfully distinguished the R from the S biotype, but in vitro ALS assays are the simplest and the quickest. The in vitro ALS assay was chosen as the standard procedure for future confirmation of resistance in monochoria populations. Caution is needed because the in vitro assay is not appropriate in cases wherein the resistance mechanism is increased metabolism of the herbicide or overexpression of the target enzyme. Results should be interpreted in relation to field history and field observations. Follow-up studies also are needed to verify that other resistance mechanisms do not confound the in vitro assay.

CGA-362622 has been registered for postemergence (POST) over-the-top or POST-directed application in cotton. Research was conducted during 1998 in Texas to determine potential cotton phytotoxicity after POST application of CGA-362622 alone and with the insecticides acephate, dicrotophos, azinphos methyl, oxamyl, thiamethoxam, dimethoate, and malathion and to determine the response of four cotton cultivars to CGA-362622 applied alone. CGA-362622 applied with malathion injured cotton more than either pesticide applied alone, and yield was reduced in one of four locations when the pesticides were applied in mixture compared with nontreated cotton. Pyrithiobac or CGA-362622 mixed with malathion injured cotton similarly. The other insecticides tank mixed with CGA-362622 generally did not adversely affect cotton. The cotton cultivars ‘Delta and Pine Land 50’, ‘Paymaster 1220’, ‘Paymaster 1220RR’, and ‘Stoneville 474’ responded similarly to CGA-362622 applied alone or with insecticides.

Bensulfuron-methyl (BSM) has been one of the most widely used herbicides in Chilean rice fields because it controls a wide spectrum of weeds and does not require field drainage for application. However, failures of BSM to control water plantain in rice fields have been noted since 2002. We assessed BSM effects on suspected resistant (CU1 and CU2) and susceptible (AN1) water plantain accessions collected in Chilean rice fields during 2004 and 2005. BSM rates resulting in 50% growth reduction () of CU2 and CU1 plants were 12- and 33-fold higher than for AN1 plants, respectively. Acetolactate synthase (ALS) activity assays in vitro suggested resistance in CU1 and CU2 was due to an ALS enzyme with reduced BSM sensitivity compared to the AN1 biotype. Resistance indices (RI), or ratios of the resistant to susceptiblevalues (BSM rate to inhibit ALS-enzyme activity by 50%), were 266 (CU2/AN1) and > 38,462 (CU1/AN1). This agreed with in vivo ALS activity assays where RI were 224 (CU2/AN1) and > 8,533 (CU1/AN1). Resistance levels detected in whole-plant or in vivo ALS activity assays were orders of magnitude lower than those detected in in vitro ALS activity studies suggesting nontarget site mechanisms may have mitigated BSM toxicity. However, a consistent ranking of BSM sensitivity levels (AN1 > CU2 > CU1) throughout all three types of assays suggests resistance is primarily endowed by low target site sensitivity. We conclude that susceptible and resistant water plantain biotypes coexist in Chilean paddies, and the use of integrated weed management involving herbicides with a different mode of action would be imperative to prevent further evolution of resistance to BSM and possibly cross-resistance to other ALS inhibitors. In vitro ALS-enzyme assays provided the best discrimination of resistance levels between biotypes.