Dennis C. Odero

Response of Giant Reed (Arundo donax) to Asulam and Trifloxysulfuron

Abstract Giant reed has been proposed as a bioenergy crop in the sugarcane production region of south Florida, where it has a high invasive potential. In an effort to limit future invasion of giant reed escapes in sugarcane, currently labeled sugarcane herbicides asulam and trifloxysulfuron were evaluated for its management. Greenhouse and field dose–response studies were conducted at the Everglades Research and Education Center in Belle Glade, FL, between 2010 and 2011. Herbicides were applied at rates ranging from 0.46 to 7.4 kg ha−1 asulam and 2 to 32 g ha−1 trifloxysulfuron, which represent 0.125× to 2× sugarcane labeled use rates, respectively. In the greenhouse, asulam and trifloxysulfuron reduced giant reed relative shoot dry weight by a maximum of 50% at 21 d after treatment (DAT). The probability of giant reed resprouting 35 d following herbicide treatment was greater for trifloxysulfuron when compared with asulam. In the field, it was predicted that a maximum of 69 and 55% giant reed control occurred with application of asulam and trifloxysulfuron, respectively, at 14 DAT. Relative shoot dry weight of giant reed treated with asulam and trifloxysulfuron was reduced by a maximum of 43% at 42 DAT. Application of asulam and trifloxysulfuron did not provide complete control of giant reed at twice the labeled sugarcane use rate, indicating that control of established giant reed in sugarcane with currently available herbicides would not be an option. Nomenclature: Asulam; trifloxysulfuron; giant reed, Arundo donax L.; sugarcane, Saccharum spp. hybrids.

Wild Buckwheat (Polygonum convolvulus) Interference in Sugarbeet

Abstract Field studies were conducted in Powell, WY in 2006 and 2007 to determine the influence of season-long interference of various wild buckwheat densities and duration of interference on sugarbeet. Percent sucrose content was not affected by wild buckwheat interference. Root and sucrose yield loss per hectare increased as wild buckwheat density increased. The estimated percent yield loss as wild buckwheat density approaches infinity was 64 and 61% for root and sucrose yield loss, respectively. The estimated percent yield loss per unit weed density at low weed densities was 6% for both root and sucrose yield loss. Greater durations of wild buckwheat interference had a negative effect on sugarbeet root yield. The critical timing of weed removal (CTWR) to avoid 5 and 10% root yield loss was 32 and 48 d after sugarbeet emergence (DAE), respectively. These results show that wild buckwheat is competitive with sugarbeet and should be managed appropriately to forestall any negative effects on sugarbeet root and sucrose yield. Nomenclature: Wild buckwheat, Polygonum convolvulus L. POLCO; sugarbeet, Beta vulgaris L

Biology and management of sugarcane yellow leaf virus: an historical overview

Sugarcane yellow leaf virus (SCYLV) is one of the most widespread viruses causing disease in sugarcane worldwide. The virus has been responsible for drastic economic losses in most sugarcane-growing regions and remains a major concern for sugarcane breeders. Infection with SCYLV results in intense yellowing of the midrib, which extends to the leaf blade, followed by tissue necrosis from the leaf tip towards the leaf base. Such symptomatic leaves are usually characterized by increased respiration, reduced photosynthesis, a change in the ratio of hexose to sucrose, and an increase in starch content. SCYLV infection affects carbon assimilation and metabolism in sugarcane, resulting in stunted plants in severe cases. SCYLV is mainly propagated by planting cuttings from infected stalks. Phylogenetic analysis has confirmed the worldwide distribution of at least eight SCYLV genotypes (BRA, CHN1, CHN3, CUB, HAW, IND, PER, and REU). Evidence of recombination has been found in the SCYLV genome, which contains potential recombination signals in ORF1/2 and ORF5. This shows that recombination plays an important role in the evolution of SCYLV.

Response of Ragweed Parthenium (Parthenium hysterophorus) to Saflufenacil and Glyphosate

Abstract Field and greenhouse studies were conducted in Belle Glade, FL, in 2010 and 2011 to evaluate saflufenacil and glyphosate efficacy on POST burndown of ragweed parthenium. Log-logistic models were used to determine the herbicide dose required to produce 90% control (ED90). The ED90 for rosette ragweed parthenium control in the greenhouse was saflufenacil at 8.0 g ai ha−1 at 14 d after treatment. The rate required to cause 90% growth reduction of rosette ragweed parthenium at 14 d after treatment was 8.9 g ha−1 of saflufenacil. The probability of rosette ragweed parthenium survival decreased with increasing rates of saflufenacil. The ED90 value for bolted ragweed parthenium control in the field was 5.7 g ha−1 of saflufenacil at 21 d after treatment. Ragweed parthenium had no response to glyphosate either in the field or in the greenhouse studies. This demonstrates that saflufenacil can be used as a POST burndown of ragweed parthenium populations that have no response to glyphosate. Nomenclature: Glyphosate; saflufenacil; ragweed parthenium, Parthenium hysterophorus L.

Phosphorus Application Influences the Critical Period of Weed Control in Lettuce

Abstract Field studies were conducted in 2010 and 2011 at Belle Glade, FL, to evaluate the influence of phosphorus (P) applications (98, 196, and 293 kg P ha−1) on the critical period of weed control (CPWC) in lettuce. Natural populations of mixed weed species were allowed to interfere with lettuce in a series of treatments of both increasing duration of weed interference and the duration of weed-free period imposed within 98, 196, and 293 kg P ha−1 levels added to the soil. The beginning and end of the CPWC for each P fertilization level based on a 5% acceptable marketable fresh lettuce yield loss level was determined by fitting log-logistic and Gompertz models to represent the increasing duration of weed interference and the duration of weed-free period, respectively. The CPWC in lettuce was estimated to be 4.6, 3.4, and 2.3 wk at 98, 196, and 293 kg P ha−1, respectively. The beginning of the CPWC was delayed at the highest P fertilization level (293 kg P ha−1), whereas the end of the CPWC was hastened at the same P fertilization level. Our study shows that inadequate levels of P fertilization in lettuce result in the need for more-intensive weed management practices to attain acceptable yields. Nomenclature: Lettuce, Lactuca sativa L.

Lanceleaf Sage (Salvia reflexa) Interference in Sugarbeet

Abstract Field studies were conducted in Powell, WY, in 2006 and 2007 to determine the influence of season-long interference of various lanceleaf sage densities and durations of interference on sugarbeet. The rectangular hyperbola model with the asymptote (A) constrained to 100% maximum yield loss characterized the relationship between lanceleaf sage density and sugarbeet yield loss. The estimated parameter I (yield loss per unit weed density as density approaches zero) was 3% for both root and sucrose yield loss. Increasing duration of lanceleaf sage interference had a negative effect on sugarbeet root yield. The critical timing of weed removal to avoid 5 and 10% root yield loss was 37 and 52 d after sugarbeet emergence, respectively. Lanceleaf sage interference did not affect percentage of sucrose content. These results indicate that lanceleaf sage is not as competitive as other weeds but that appropriate control measures should be undertaken to minimize sugarbeet yield loss from interference. Nomenclature: Lanceleaf sage, Salvia reflexa Hornem. SALRE; sugarbeet, Beta vulgaris L.

Venice Mallow (Hibiscus trionum) Interference in Sugarbeet

Abstract Field studies were conducted in Powell, WY, in 2006 and 2007 to determine the influence of season-long interference of various Venice mallow densities and duration of interference on sugarbeet. Sucrose concentration was not affected by Venice mallow interference. The effect of Venice mallow density on sugarbeet root and sucrose yield loss was described by the rectangular hyperbola model. Root and sucrose yield loss increased as Venice mallow density increased. The estimated asymptote, A (percent yield loss as density approaches infinity) was 61% for both root and sucrose yield loss, and the estimated parameter, I (percent yield loss per unit weed density as density approaches zero) was 6% for both root and sucrose yield loss. Sugarbeet root yield decreased as the duration of Venice mallow interference increased. The critical timing of weed removal to avoid 5 and 10% root yield loss was 30 and 43 d after sugarbeet emergence, respectively. Results show that Venice mallow is competitive with sugarbeet implying that it should be managed appropriately to reduce negative effects on yield and prevent seed bank replenishment and re-infestation in subsequent years. Nomenclature: Venice mallow, Hibiscus trionum L. HIBTR; sugarbeet, Beta vulgaris L.

Dissipation of Pendimethalin in Organic Soils in Florida

Abstract Understanding the persistence of PRE-applied pendimethalin is important in determining timing of subsequent weed management programs in sugarcane on organic soils in the Everglades Agricultural Area (EAA). Dissipation of oil- and water-based pendimethalin formulations applied PRE at 2, 4, and 8 kg ai ha−1 were compared in 2011 and 2012 on organic soils in the EAA. The rate of dissipation of both formulations was very similar. Both formulations had an initial rapid rate of dissipation followed by a slower rate of dissipation. However, the initial amount of pendimethalin in the soil was higher with the water-based compared to the oil-based formulation, most likely because of the lower volatility of the water-based formulation. The half-lives (DT50s) of the oil-based formulation were 32, 18, and 10 d and 8, 8, and 12 d at 2, 4, and 8 kg ha−1, respectively, in 2011 and 2012, respectively. The DT50s of the water-based formulation were 20, 13, and 10 d and 12, 12, and 14 d at 2, 4, and 8 kg ha−1, respectively in 2011 and 2012, respectively. These DT50 values were attributed to low soil water content as well as the absence of incorporation following application. Our results suggest that dissipation of pendimethalin is rapid on organic soils irrespective of the formulation when applied under dry soil conditions with no incorporation into the soil. Nomenclature: Pendimethalin; sugarcane; Saccharum spp. hybrids. Resumen Entender la persistencia de aplicaciones PRE de pendimethalin es importante para determinar el momento de implementación de programas de manejo de malezas subsiguientes en caña de azúcar en suelos orgánicos en el Área Agrícola de los Everglades (EAA). En 2011 y 2012, se comparó la disipación de formulaciones de pendimethalin a base de aceite y de agua aplicadas PRE a 2, 4, y 8 kg ai ha−1 en suelos orgánicos en el EAA. La tasa de disipación de ambas formulaciones fue muy similar. Ambas formulaciones tuvieron una tasa inicial de disipación rápida seguida de una tasa de disipación más lenta. Sin embargo, la cantidad inicial de pendimethalin en el suelo fue mayor con la formulación a base de agua en comparación con la formulación a base de aceite. Esto es probable que se debiera a la baja volatilidad de la formulación a base de agua. Las vidas medias (DT50s) de la formulación a base de aceite fueron 32, 18, y 10 d y 8, 8, y 12 d a 2, 4, y 8 kg ha−1, en 2011 y 2012, respectivamente. Las DT50s de la formulación a base de agua fueron 20, 13, y 10 d y 12, 12, y 14 d a 2, 4, y 8 kg ha−1, en 2011 y 2012, respectivamente. Estos valores de DT50s fueron atribuidos al bajo nivel de humedad de suelo y a la ausencia de incorporación después de la aplicación. Nuestros resultados sugieren que la disipación de pendimethalin es rápida en suelos orgánicos independientemente de la formulación cuando se aplica sin incorporación a suelos en condiciones secas.

Response of Sweet Corn to Pyroxasulfone in High-Organic-Matter Soils

Abstract Field experiments were conducted in 2011 and 2012 in Belle Glade, FL to evaluate the response of sweet corn and weed control to pyroxasulfone on high-organic-matter soils in the Everglades Agricultural Area (EAA) of southern Florida with the use of dose-response curves. Pyroxasulfone was applied PRE at 31.25, 62.5, 125, 250, 500, and 1,000 g ai ha−1 on soil with 80% organic matter. Dose-response curves based on a three-parameter log-logistic model were used to determine pyroxasulfone rate required to provide 90% control (ED90) of spiny amaranth, common lambsquarters, and common purslane in sweet corn. The ED90 values for spiny amaranth, common lambsquarters, and common purslane control were 209, 215, and 194 g ha−1 of pyroxasulfone, respectively, at 21 d after treatment (DAT). At 42 DAT, the ED90 values for spiny amaranth, common lambsquarters, and common purslane control were 217, 271, and 234 g ha−1 of pyroxasulfone, respectively. Sweet corn yield increased with increasing rates of pyroxasulfone. An estimated 214 g ha−1 of pyroxasulfone was required to maintain sweet corn yield at 90% level of the weed-free yield. In addition, pyroxasulfone did not result in sweet corn injury. These results indicate that pyroxasulfone can provide effective weed control in sweet corn on high-organic-matter soils of the EAA. Nomenclature: Pyroxasulfone; common lambsquarters, Chenopodium album L. CHEAL; common purslane, Portulaca oleracea L. POROL; spiny amaranth, Amaranthus spinosus L. AMASP; sweet corn, Zea mays L. Resumen Se realizaron experimentos de campo en 2011 y 2012 en Belle Glade, FL para evaluar la respuesta del maíz dulce y el control de malezas a pyroxasulfone en suelos con alta contenido de materia orgánica en el Área Agrícola de Everglades (EAA) en el sur de Florida, usando curvas de respuesta a dosis. Se aplicó pyroxasulfone PRE a 31.25, 62.5, 125, 250, 500 y 1,000 g ai ha−1 en suelo con 80% materia orgánica. Se usaron curvas de respuesta a dosis basadas en un modelo log-logístico de tres parámetros para determinar la dosis requerida de pyroxasulfone para obtener 90% de control (ED90) de Amaranthus spinosus, Chenopodium album, y Portulaca oleracea en maíz dulce. Los valores de ED90 para el control de A. spinosus, C. album, y P. oleracea fueron 209, 215 y 194 g ha−1 de pyroxasulfone, respectivamente. El rendimiento del maíz dulce incrementó con dosis crecientes de pyroxasulfone. Se requirió un estimado de 214 g ha−1 de pyroxasulfone para mantener el rendimiento del maíz dulce a un nivel de 90% del rendimiento con cero malezas. Adicionalmente, pyroxasulfone no causó daño al maíz dulce. Estos resultados indican que pyroxasulfone puede brindar control efectivo de malezas en maíz dulce en suelos con alto contenido de materia orgánica en el EAA.

Response of energycane to preemergence and postemergence herbicides.

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 S-metolachlor 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. Nomenclature: Ametryn; asulam; atrazine; carfentrazone; clethodim; clomazone; 2,4-D amine; dicamba; diuron; flumioxazin; glufosinate; glyphosate; halosulfuron; hexazinone; mesotrione; metribuzin, paraquat; S-metolachlor; sethoxydim; trifloxysulfuron; energycane, Saccharum spp. × Saccharum spontaneum ‘UFCP 78-1013′, ‘UFCP 82-1655′; sugarcane, Saccharum officinarum L. La caña energética ha sido propuesta como un cultivo bioenergético potencial para la producción de combustibles lignocelulósicos en los Estados Unidos. Los herbicidas usados actualmente en caña de azúcar y otros cultivos pueden ser potencialmente usados en caña energética si la tolerancia es aceptable. También, para limitar invasiones producto de escapes de caña energética, los herbicidas usados para el control de gramíneas perennes podrían potencialmente ser usados para el manejo de estos escapes. Estudios con potes fueron realizados a la intemperie, en donde se midió la biomasa de la caña energética sobre y dentro del suelo para evaluar la tolerancia a 9 herbicidas PRE y 19 herbicidas POST usados en caña de azúcar y otros cultivos. La aplicación PRE de atrazine, diuron, mesotrione, metribuzin, pendimethalin, y S-metolachlor a dosis de etiqueta para caña de azúcar no causaron un daño significativo (<3%) ni redujeron la biomasa de la caña energética al compararse con plantas sin tratamiento, a 28 y 56 días después del tratamiento (DAT). El daño causado por flumioxazin fue transitorio y no se observó a 56 DAT. A 56 DAT, el daño en la caña energética aumentó a 71 y 98%, respectivamente, para clomazone y hexazinone. Hexazinone y clomazone aplicados PRE redujeron significativamente la biomasa al compararse con las plantas sin tratamiento. A 28 DAT, aplicaciones POST de 2,4-D amine, ametryn, asulam, atrazine, carfentrazone, dicamba, halosulfuron, mesotrione, metribuzin, y trifloxysulfuron a las dosis de etiqueta para caña de azúcar no dañaron o redujeron significativamente la biomasa de la caña energética en comparación con las plantas testigo. Se observó daño cuando se aplicó POST clethodim (99%), clomazone (51%), diuron (51%), flumioxazin (21%), glufosinate (84%), glyphosate (100%), hexazinone (100%), paraquat (66%), y sethoxydim (100%), y cada uno de estos tratamientos redujo la biomasa de la caña energética en comparación con las plantas sin tratamiento. Estos resultados pueden ser potencialmente usados en el control de malezas en caña energética. También, con base en nuestros resultados, clethodim, glyphosate, y sethoxydim podrían ser efectivos para el manejo de escapes de caña energética.