Abstract Winter wild oat [Avena sterilis ssp. ludoviciana (Durieu) Gillet & Magne; referred to as A. sterilis here] is one of the major weed species of the Avena genus, given its high competitive ability to infest cereal crops worldwide, with special concern in Spain. A nine-location field experiment was established across Spain where a total of 400 A. sterilis seeds per location were sowed in four replicates in autumn 2016 to monitor the emergence during two growing seasons in dryland conditions. The data were used to test the prediction ability of previously published thermal (TT) and hydrothermal time (HTT) models and to develop new models, if required. Overall, the average percentage of emergence was 30% during the first season and 21% during the second season. In both seasons, the main emergence flush occurred between November and February. According to the phenological stage, A. sterilis achieved the tillering earlier in southern sites, between November 25 and the end of December, compared with northern sites, where this stage was reached at the end of January. The newly developed model described the emergence with precision, using three cardinal temperatures to estimate the TT. The three cardinal points were established at –1.0, 5.8, and 18.0 C for base (Tb), optimum (To), and ceiling temperature (Tc), while the base water potential (Ψb) was established at –0.2 MPa for the HTT estimation. This study contributes to improving prediction of the emergence of A. sterilis and provides knowledge for decision support systems (DSS) for the control of this weed.

AbstractDissipation of S-metolachlor, a soil-applied herbicide, on organic and mineral soils used for sugarcane production in Florida was evaluated using field studies in 2013 to 2016. S-metolachlor was applied PRE at 2,270 g ha−1 on organic and mineral soils with 75% and 1.6% organic matter, respectively. The rate of dissipation of S-metolachlor was rapid on mineral soils compared with organic soils. Dissipation of S-metolachlor on organic soils followed a negative linear trend resulting in half-lives (DT50) ranging from 50 to 126 d. S-metolachlor loss on organic soils was more rapid under high soil-moisture conditions than in corresponding low soil-moisture conditions. On mineral soils, dissipation of S-metolachlor followed an exponential decline. The DT50 of S-metolachlor on mineral soils ranged from 12 to 24 d. The short persistence of S-metolachlor on mineral soils was likely attributed to low organic matter content with limited adsorptive capability. The results indicate that organic matter content and soil moisture are important for persistence of S-metolachlor on organic and mineral soils used for sugarcane production in Florida.

North African knapweed (Centaurea diluta Aiton) is an annual weed that is widespread in southern Spain and is of increasing concern in dryland cropping systems. Despite its expanding range in Spain, there is limited information on the emergence timing and pattern of this species, knowledge of which is critical for developing more timely and effective management strategies. Therefore, there is a need to develop simple and reliable models to predict the timing and emergence of this annual weed under dryland conditions. A multi-location field experiment was established across Spain in 2016 to 2017 to assess the emergence of C. diluta. At each of 11 locations, seeds were sown in the fall, and emergence was recorded. Overall emergence averaged 39% in the first year across all sites and 11% in the second year. In both years, the main emergence flush occurred at the beginning of the growing season. A three-parameter Weibull function best described seedling emergence of C. diluta. Emergence models were developed based on thermal time (TT) and hydrothermal time (HTT) and showed high predictability, as evidenced by root mean-square error prediction values of 10.8 and 10.7, respectively. Three cardinal points were established for TT and HHT at 0.5, 10, and 35 C for base, optimal, and ceiling temperatures, respectively, while base water potential was estimated at -0.5 MPa.

Lolium rigidum Gaudin is a troublesome weed worldwide, and its distribution may increase due to climate change. It has become resistant to several herbicides and, therefore, its control is problematic. On the other hand, its seed biology, with little dormancy and short-term viability, can play a major role in reducing its seed bank, which would improve control of this weed. For this reason, knowledge of the emergence patterns of this species entails improvements for its management. In this work seeds from one population of L. rigidum, collected in Northeastern Spain, were distributed and sown in 11 sites across Spain, and its emergence was followed every 2–7 days for two growing seasons (2016-17 and 2017–18). These emergence sequences were compared with previously published thermal time and hydrothermal time based models, and new models were developed afterwards. The hydrothermal time based model did not significantly improve models based solely on thermal time. The accuracy of these newly developed models varied from site to site, but in general, they worked better for Northern locations than for Southern locations. Thus, the experimental sites were split between North and South, and specific models for each region were developed. The model developed for Northern sites worked very well, but the one for Southern sites needs improvement. This works reveals that, with regard to this weed species, probably different models should be developed for different climatic conditions. The model developed with data from Northern sites should be validated with local populations, while the one developed with data from Southern sites will probably need to be revised or newly developed with data from more Southern populations.

Currently, the rice stink bug complex (Hemiptera: Pentatomidae) attacking Florida rice is the most diversified and unique stink bug complex in United States rice production. This complex includes the common rice stink bug, Oebalus pugnax (F.), and two invasive species, Oebalus ypsilongriseus (DeGeer) and Oebalus insularis (Stal). Insecticidal efficacy for these two invasive species is not known. Insecticidal evaluations of five insecticides were made on adults of both sexes of the three species. Weights of adults were also determined. In all three species, females weighed more than males of the same species. Also, O. pugnax adults were the largest followed by O. ypsilongriseus, with O. insularis being the smallest adults. All five insecticides gave a high degree of control of 93-100% for both sexes of all three species. These data are currently useful to Florida rice growers and may be useful to rice growers in other states if the two invasive species spread to those states. These data also provide baseline data for future studies on development of insecticide resistance of the stink bugs in Florida rice.

Abstract Sugarcane growers in Florida have been reporting reduced control of fall panicum with asulam, the main herbicide used for POST grass control. Therefore, outside container experiments were conducted to determine the response of four fall panicum populations from Florida to asulam applied alone and to evaluate whether tank-mix combination with trifloxysulfuron enhances control. Asulam was applied at 230 to 7,400 g ai ha − 1, corresponding to 1/16 to 2X the maximum labeled rate for a single application in sugarcane, with or without combination with trifloxysulfuron at 16 g ai ha − 1. Three fall panicum populations were collected from fields in which reduced control had been reported, while one population was from a field not used for sugarcane production but adjacent to a sugarcane field. The potency of asulam based on ED50 values (the rate required to cause 50% dry weight reduction at 28 d after treatment) ranged from 2,249 to 5,412 g ha − 1 for tolerant populations with reported reduced fall panicum control compared with 1,808 g ha − 1 for the susceptible population from the field not used for sugarcane production, showing that the latter was most sensitive to asulam. Addition of trifloxysulfuron to asulam increased potency on fall panicum by 5- to 15-fold, indicating that the tank mix enhanced dry weight reduction for all populations. The probability of fall panicum survival (regrowth after aboveground biomass harvesting) at the labeled rate of asulam ranged from 2% to 47% compared with 0% to 6% when trifloxysulfuron was added to the tank mix. Our results show differential response of fall panicum populations in Florida to asulam, which can be overcome by tank mixing with trifloxysulfuron even for populations that are difficult to control in sugarcane, but no evolution of resistance to asulam. Nomenclature:Asulam; trifloxysulfuron; fall panicum; Panicum dichotomiflorum Michx. PANDI; sugarcane, Saccharum spp.

Field experiments were conducted in Citra, FL, and Tifton, GA, to evaluate simulated drift of dicamba and 2,4-D on cotton. Drift applications were made at the sixth leaf and first square growth stages using variable and constant carrier volumes and the same herbicide rate. Drift applied using variable carrier volumes were proportionally reduced with the herbicide rate while drift applied at constant carrier volumes were all made at 140 L ha(-1), regardless of herbicide rate. At 21 DAT, dicamba applied at variable carrier volumes reduced cotton heights 8% [from nontreated check (NTC)] compared to no change in height with dicamba applied at constant carrier volumes. The same effect was seen with 2,4-D applied at first square where variable carrier volumes decreased cotton heights 18% (from NTC) compared to 2% at 140 L ha(-1). Cotton yields were reduced to 70% of NTC when dicamba was applied at sixth leaf at variable carrier volumes compared to 87% at constant carrier volumes. The same response was seen with 2,4-D applied at sixth leaf where variable carrier volumes reduced cotton yields to 19% of NTC compared to 32% at constant carrier volumes. Cotton injury, height, boll production, and yield were all affected by drift carrier volume. When simulating herbicide drift in the future, it is critical to use variable carrier volumes for application as constant carrier volumes have shown to decrease the amount of plant injury observed.

Field experiments were conducted to determine weed control and radish ( Raphanus sativus ) response to S -metolachlor on organic soil in the Everglades Agricultural Area (EAA) using a dose–response bioassay. S -metolachlor was applied preemergence at 0.35, 0.7, 1.4, 2.8, 5.6, and 11.2 kg·ha −1 . The rate of S -metolachlor required to provide 90% weed control (ED 90 ) and result in 5% and 10% radish injury were determined by fitting a three-parameter log-logistic model. The ED 90 values for common lambsquarters, spiny amaranth, and fall panicum control were 2.7, 1.6, and 1.2 kg·ha −1 of S -metolachlor, respectively, at 14 days after treatment (DAT). At 28 DAT, the ED 90 values were 3.8, 1.9, and 1.5 kg·ha −1 of S -metolachlor, respectively. Injury on radish increased as S -metolachlor rates increased with maximum injury of 24% and 19% at 14 and 28 DAT, respectively. S -metolachlor at 2.1 and 3.1 kg·ha −1 at 14 DAT and 2.6 and 3.7 kg·ha −1 at 28 DAT would result in 5% and 10% radish injury, respectively. Radish yield decreased with increasing rates of S -metolachlor. At the proposed S -metolachlor use rate of 1.4 kg·ha −1 for root crops, radish yield was 80% of the weed-free yield probably resulting from competition from common lambsquarters, which was controlled 74%. These results show that preemergence S -metolachlor would provide effective control of spiny amaranth and fall panicum in radish on organic soils of the EAA at the proposed use rate for root crops while about three times the proposed use rate would be required to provide effective common lambsquarters control. This implies that infestation of common lambsquarters on radish fields on organic soils will not be effectively controlled by S -metolachlor at the proposed use rate resulting in yield reduction.

As dicamba resistance traits become more common in agronomic crops, the potential for off-site movement also increases. Little is known of how common vegetable crops will respond to dicamba drift. The objective of this study was to evaluate the effect of dicamba and glyphosate drift on bell pepper and squash growth as a function of application timing. The treatments were arranged in a factorial design with two timings by three rates and a nontreated check. The two timings were early bloom and midbloom (during bloom when fruit were present). The three rates were glyphosate at 21 + dicamba at 14 g ha−1, glyphosate at 10 + dicamba at 7 g ha−1, and glyphosate at 7 + dicamba 5 at g ha−1. Herbicides were applied with a controlled droplet applicator calibrated to deliver 2.34 L ha−1. In squash, crop injury was 26 to 31% at 3 DAT and 48 to 65% at 17 DAT. However, no differences were measured among application timings or rates for fruit weight or number at individual harvest or season total. Bell pepper injury ranged between 0 and 8% from 3 to 17 DAT and was not significantly different than the nontreated. However, large, Fancy, marketable, and total bell pepper fruit number were greater in the nontreated than glyphosate at 21 + dicamba 14 at g ha−1and glyphosate at 10 + dicamba at 7 g ha−1both years. The three rates of dicamba + glyphosate had a greater number and weight of cull fruit compared to the number of fruit in the nontreated plots. The cull fruit were shorter with a flattened appearance. Leaving bell pepper fruit on the plants longer may result in small and medium fruit becoming large or Fancy grade bell pepper fruit.

The importance of PRE herbicide applications in cotton has increased since the evolution of glyphosate-resistant (GR) Palmer amaranth. Cotton producers are relying on residual herbicides for control of Palmer amaranth, as POST options are limited or ineffective.S-Metolachlor, acetochlor, fomesafen, and dicamba all provide PRE control of Palmer amaranth; however, little is known about the effect of irrigation rate on incorporation and herbicidal efficacy. In 2015, an experiment was conducted on fine sand and loamy sand soils to evaluate the influence of irrigation volume (0.0 to 12.7 mm ha−1) on Palmer amaranth control with PRE herbicides. Irrigation volume after herbicide application was significant for bothS-metolachlor and acetochlor. Efficacy ofS-metolachlor was greatest in plots receiving 6.4 and 12.7 mm of irrigation where Palmer amaranth biomass was reduced to 4 and 2% of a nontreated control (NTC), respectively, compared with 61% in plots with the 0-mm irrigation treatment. Palmer amaranth control by acetochlor incorporated at 3.2- to 12.7-mm irrigation did not differ but did reduce Palmer amaranth biomass compared with the 1.6-mm irrigation rate. Irrigation volume was not significant for the soil incorporation of fomesafen or dicamba. Across all herbicides, fomesafen-treated plots provided the most consistent control of Palmer amaranth, reducing its biomass to < 3% of NTC at all irrigation rates. Dicamba provided the least and most inconsistent control of Palmer amaranth, producing 17 to 51% of NTC biomass.

Growers have observed lack of control of ragweed parthenium with glyphosate at 0.84 kg ae ha−1 used for weed control in noncrop areas and fallow fields in the Everglades Agricultural Area (EAA) of South Florida. Therefore, studies were conducted to (1) confirm and characterize the level of glyphosate resistance in ragweed parthenium from the EAA, (2) determine if reduced absorption or translocation is the mechanism of resistance of ragweed parthenium to glyphosate, and (3) evaluate the efficacy of POST herbicides commonly used in cultivated and noncrop areas for broadleaf weed control on flowering ragweed parthenium at the full and half labeled rate. A dose-response bioassay was used to determine the response of the rosette ragweed parthenium biotype from the EAA (resistant) and a susceptible biotype from Stoneville, MS, to glyphosate. The bioassay showed that the resistant biotype was 40- to 43-fold less sensitive to glyphosate when compared to the susceptible biotype. There was no significant difference in glyphosate absorption or translocation from the treated leaf to the rest of the plant 168 h after treatment between resistant and susceptible biotypes. This shows that absorption or translocation is not a mechanism of glyphosate resistance by ragweed parthenium. Saflufenacil + dimethenamid-P and hexazinone provided rapid and complete control of flowering ragweed parthenium 3 wk after treatment (WAT). Aminocyclopyrachlor + chlorsulfuron and aminopyralid at the full and the half label rates provided 100% control of ragweed parthenium by 9 WAT. Clopyralid, 2,4-D amine, and glufosinate at the full label rate provided 89 to 98% control of ragweed parthenium 9 WAT. Control of ragweed parthenium 9 WAT was < 75% with flumioxazin, fomesafen, glyphosate, imazapic, imazethapyr, mesotrione, oxyfluorfen, and paraquat, irrespective of use rate.

Parthenium hysterophorus is an aggressive annual weed of tropical and subtropical environments commonly associated with noncrop areas in the sugarcane production region of Florida but is now encroaching into cultivated fields. Greenhouse studies were conducted to evaluate the potential phytotoxic effect of P. hysterophorus residue on germination and early growth of sugarcane on organic and minerals soils of Florida. P. hysterophorus dry residue was mixed with both soils at 0, 132, 264, 527, 1054, 2108, 4216, and 8432 g of P. hysterophorus dry residue per m(-3) of soil. The weight of P. hysterophorus was based on the dry biomass of average current field infestation of 32 plants m(-2) in fallow sugarcane fields, and the volume of the planting media was based on an area of a field disked at a depth of 15 cm. These rates were equivalent to 0x, 0.25x, 0.5x, 1x, 2x, 4x, 8x, and 16x the amount of P. hysterophorus dry biomass present at field infestation levels in Florida based on an area of a field disked at a depth of 15 cm. Results showed that on mineral soil, sugarcane germination, height, aboveground and belowground biomass decreased <5% in response to P. hysterophorus residue at the current infestation level in Florida. In contrast, P. hysterophorus residue had no effect on sugarcane germination, height, aboveground and belowground biomass on organic soil. These results show that there is no potential adverse effect of P. hysterophorus residue on sugarcane grown on mineral and organic soils in Florida at the current infestation level in cultivated fields. (C) 2015 Elsevier Ltd. All rights reserved.

Energycane has been proposed as a potential, perennial bioenergy crop for lignocellulosic-derived fuel production in the United States. Herbicides currently used in sugarcane and other crops can potentially be used in energycane if there is acceptable tolerance. Also, to limit future invasion of energycane escapes, herbicides used for perennial grass control could potentially be used for management of escapes. In container studies conducted outside, aboveground and belowground biomass of energycane was measured to evaluate energycane tolerance to 9 PRE and 19 POST herbicides used in sugarcane and other crops. PRE application of atrazine, diuron, mesotrione, metribuzin, pendimethalin, and Smetolachlor at rates labeled for sugarcane did not significantly injure (<3%) or reduce energycane biomass compared with the nontreated plants 28 and 56 d after treatment (DAT). Injury from clomazone (54%), flumioxazin (7%), and hexazinone (29%) was observed 28 DAT. Injury from flumioxazin was transient and was not observed at 56 DAT. At 56 DAT, energycane injury increased to 71 and 98%, respectively, for clomazone and hexazinone. Hexazinone and clomazone applied PRE significantly reduced biomass compared with the nontreated plants. At 28 DAT, POST application of 2,4-D amine, ametryn, asulam, atrazine, carfentrazone, dicamba, halosulfuron, mesotrione, metribuzin, and trifloxysulfuron at labeled rates for sugarcane did not injure or significantly reduce energycane biomass compared with the nontreated plants. Injury was observed when clethodim (99%), clomazone (51%), diuron (51%), flumioxazin (21%), glufosinate (84%), glyphosate (100%), hexazinone (100%), paraquat (66%), and sethoxydim (100%) were applied POST, and each of these treatments reduced energycane biomass compared with the nontreated plants. These results show that several PRE and POST herbicides used for weed management in sugarcane may potentially be used in energycane for weed control. Also, based on our results, clethodim, glyphosate, and sethoxydim would be effective for management of energycane escapes.

Pyraflufen-ethyl is a phenylpyrazole herbicide for control of annual and perennial broadleaf weeds. Greenhouse and field studies were conducted to determine pyraflufen-ethyl efficacy for control of Parthenium hysterophorus at the rosette and flowering stages, respectively. Both growth stages were treated with pyraflufen-ethyl at six rates ranging from 0.46 to 14.60 g a.i. ha(-1). Aboveground dry weight of rosette P. hysterophorus was reduced 90% by pyraflufen-ethyl at 2.33-2.65 g a.i. ha(-1) 14 days after treatment (DAT). At the label use rate of 0.91-3.64 g a.i. ha(-1) for control of broadleaf weeds, pyraflufenethyl was estimated to provide 13-58% and 5-32% control of flowering P. hysterophorus 60 and 87 cm in height, respectively at 21 DAT. These results show that pyraflufen-ethyl can control rosette P. hysterophorus within the label use rate for broadleaf weeds. However, rates higher than the label use rate are required for control of flowering P. hysterophorus, showing that pyraflufen-ethyl must be applied at the early stages of P. hysterophorus growth for effective control. (C) 2013 Elsevier Ltd. All rights reserved.

There are limited PRE herbicide options available to provide residual weed control in sweet corn grown on organic soils in the Everglades Agricultural Area (EAA). Field studies were established to determine the efficacy of PRE applied saflufenacil + dimethenamid-P at six rates ranging from 10 + 88 to 319 + 2802 g ai ha−1 on weed control and sweet corn tolerance on organic soils in the EAA in 2011 and 2012. Saflufenacil + dimethenamid-P is a premix recently labeled for PRE weed control in field corn at 50 + 438 to 90 + 788 g ha−1 depending on soil texture. There was no phytotoxic effect of PRE applied saflufenacil + dimethenamid-P on sweet corn. At 42 d after treatment, common lambsquarters, common purslane, and spiny amaranth were controlled 90% with saflufenacil + dimethenamid-P at 58 + 508, 71 + 622, and 58 + 512 g ha−1, respectively. Sweet corn yield at 95% of the weed-free yield was estimated to be obtained at 69 + 606 g ha−1 of saflufenacil + dimethenamid-P. Our results show that saflufenacil + dimethenamid-P at 69 + 606 to 71 + 622 g ha−1 controlled three common weeds and maintained acceptable sweet corn yield. Labeled rates of saflufenacil + dimethenamid-P for field corn on mineral soils were adequate for weed control in sweet corn on organic soils.