Analiza H. M. Ramirez

Factors Affecting the Germination of Tall Morningglory (Ipomoea purpurea)

Abstract Tall morningglory is an annual broadleaf vine and a problem weed in many annual and perennial crops in several countries including the United States. A better understanding of the germination biology of tall morningglory would facilitate the development of better control strategies for this weed. Experiments were conducted under greenhouse and laboratory conditions to evaluate the effects of various environmental factors, such as temperature, light, planting depth, pH, osmotic and salt stress, and flooding duration, on the germination of tall morningglory. The results suggested that the optimum day/night temperature range for the germination of tall morningglory was 20/12.5 to 35/25 C and maximum germination (89%) was observed at 30/20 C. Temperature higher and lower than the optimum range significantly reduced germination. Alternate light and dark did not have any adverse effect on the germination of tall morningglory seeds. The germination was 10% at an osmotic stress of −0.3 and −0.4 MPa, and above that, no germination was observed. Tall morningglory showed some tolerance to salt stress. The germination was 40% and 12% at salt concentrations of 50 mM and 200 mM, respectively. Germination was affected by pH levels, and maximum germination occurred at pH 6, whereas above or below that level, germination was significantly reduced. Maximum germination of seeds was 83 and 94% when sown at 0 and 2 cm depth in soil, within a week of sowing; however, germination was significantly reduced to 76% when placed at a depth of 4 cm or deeper. Under no flooding treatment, 87% of seed germinated, but flooding delayed and inhibited the germination of tall morningglory seeds. It is concluded that several environmental factors affected the germination of tall morningglory, and this information could help to predict the spread of tall morningglory in new areas such as Florida. Nomenclature: Tall morningglory, Ipomoea purpurea (L.) Roth, PHBPU.

Local conditions, not regional gradients, drive demographic variation of giant ragweed (Ambrosia trifida) and common sunflower (Helianthus annuus) across northern U.S. maize belt.

Abstract Knowledge of environmental factors influencing demography of weed species will improve understanding of current and future weed invasions. The objective of this study was to quantify regional-scale variation in vital rates of giant ragweed and common sunflower . To accomplish this objective, a common field experiment was conducted across seven sites between 2006 and 2008 throughout the north central U.S. maize belt. Demographic parameters of both weed species were measured in intra- and interspecific competitive environments, and environmental data were collected within site-years. Site was the strongest predictor of belowground vital rates (summer and winter seed survival and seedling recruitment), indicating sensitivity to local abiotic conditions. However, biotic factors influenced aboveground vital rates (seedling survival and fecundity). Partial least squares regression (PLSR) indicated that demography of both species was most strongly influenced by thermal time and precipitation. The first PLSR components, both characterized by thermal time, explained 63.2% and 77.0% of variation in the demography of giant ragweed and common sunflower, respectively; the second PLSR components, both characterized by precipitation, explained 18.3% and 8.5% of variation, respectively. The influence of temperature and precipitation is important in understanding the population dynamics and potential distribution of these species in response to climate change. Nomenclature: Giant ragweed, Ambrosia trifida L. AMBTR; common sunflower, Helianthus annuus L. HELAN; maize, Zea mays L.; soybean, Glycine max (L.) Merr.

Tank Mixing Saflufenacil, Glufosinate, and Indaziflam Improved Burndown and Residual Weed Control

Abstract Saflufenacil and indaziflam, POST and PRE herbicides, respectively, have been registered recently for weed control in Florida citrus. Glufosinate is under evaluation and may be registered in the future for POST weed control in citrus. Citrus growers often want to have a tank mixture of herbicides that provide broad-spectrum weed control. Saflufenacil is a broadleaf herbicide and needs to be tank mixed with other herbicide(s) to increase weed control spectrum. Information is not available on interaction of saflufenacil, glufosinate, and indaziflam applied in tank mixtures on weed control efficacy. Greenhouse and field experiments were conducted at two locations (Polk and Orange County, FL) to evaluate the efficacy and potential antagonism or synergy of saflufenacil and glufosinate applied in tank mixes, and various three-way mixes with indaziflam. The results suggested that tank mixing saflufenacil with glufosinate had no effect on grass weed control, but had additive effect on broadleaf weed control. Indaziflam tank mixed at the recommended label rate (0.073 kg ha−1) provided better residual weed control compared with the lower rate (0.05 kg ha−1). Tank mixing indaziflam with saflufenacil and glufosinate improved broadleaf and grass weed control, reduced weed density, and biomass compared with tank mixing saflufenacil and glufosinate. Tank mixing indaziflam at 0.073 kg ha−1 with saflufenacil and glufosinate provided ≥ 88% control of broadleaf and grass weeds at 30 d after treatment (DAT), and it was comparable with tank mixing saflufenacil, glyphosate and pendimethalin. This treatment combination recorded the lowest weed density (≤ 7 plants m−2) and biomass (< 80 g m−2) at 60 DAT. Glyphosate applied alone was less effective than tank mixing with saflufenacil and glufosinate for broadleaf and grass weed control. This indicates additive effect of tank mixture on glyphosate efficacy. It is concluded that saflufenacil can be tank mixed with glufosinate for control of broadleaf and grass weeds; however, addition of indaziflam in tank mixture provided long-term, broad-spectrum weed control in Florida citrus compared with other treatments. Nomenclature: Glufosinate; glyphosate; indaziflam; pendimethalin; saflufenacil; citrus, Citrus spp. Resumen Saflufenacil e indaziflam son herbicidas POST y PRE, respectivamente, que han sido registrados recientemente para el control de malezas en cítricos en Florida. Glufosinate está siendo evaluado y podría ser registrado en el futuro para el control de malezas POST en cítricos. Los productores de cítricos a menudo quieren tener mezclas de herbicidas en tanque que brinden un control de malezas de amplio espectro. Saflufenacil es un herbicida para malezas de hoja ancha, el cual necesita ser mezclado en tanque con otros herbicidas para incrementar el espectro de control de malezas. No hay información disponible acerca de la interacción de saflufenacil, glufosinate e indaziflam al ser aplicados en mezclas en tanque sobre la eficacia en el control de malezas. Se realizaron experimentos de invernadero y de campo en dos localidades (condados Polk y Orange, Florida) para evaluar la eficacia y el potencial de antagonismo o sinergia de saflufenacil y glufosinate aplicados en mezcla en tanque, y de varias mezclas de tres-vías con indaziflam. Los resultados sugirieron que la mezcla en tanque de saflufenacil con glufosinate no tuvo efecto sobre el control de gramíneas, pero tuvo un efecto aditivo sobre el control de malezas de hoja ancha. La mezcla en tanque con indaziflam a la dosis recomendada (0.073 kg ha−1) brindó mejor control residual al compararse con la dosis baja (0.05 kg ha−1). El mezclar en tanque indaziflam con saflufenacil y glufosinate mejoró el control de malezas gramíneas y de hoja ancha, y redujo la densidad y biomasa de malezas en comparación con la mezcla en tanque de saflufenacil y glufosinate. La mezcla en tanque de indaziflam a 0.073 kg ha−1 brindó ≥88% de control de malezas de hoja ancha y gramíneas a 30 días después del tratamiento (DAT), y fue comparable con la mezcla en tanque de saflufenacil, glyphosate y pendimethalin. Esta combinación registró las densidades de malezas (≤7 plantas m−2) y de biomasa (<80 g m−2) más bajas a 60 DAT. Glyphosate aplicado solo fue menos efectivo que la mezcla en tanque con saflufenacil y glufosinate para el control de malezas de hoja ancha y gramíneas. Esto indica un efecto aditivo de la mezcla en tanque sobre la eficacia de glyphosate. Se concluyó que saflufenacil puede ser mezclado en tanque con glufosinate para el control de malezas de hoja ancha y gramíneas. Sin embargo, la adición de indaziflam a la mezcla en tanque brindó el mayor control de amplio espectro y larga duración en cítricos en Florida en comparación con otros tratamientos.

Germination and Emergence Characteristics of Common Beggar's-Tick (Bidens alba)

Abstract Common beggars-tick is an annual weed commonly found in citrus groves in Florida. A series of laboratory and greenhouse experiments were conducted to determine the germination response of common beggars-tick to various environmental factors that influence seed survival, germination, and dormancy. The results suggest that common beggars-tick germinated over a wide range of temperatures (15 to 40 C) and in both alternating light and dark and dark conditions. New seeds (collected in 2010) germinated better than the old seeds (collected in 2007) at 15/10 C; however, at temperatures above 35 C, the old seeds germinated better. The highest germination was 95% at 25 to 30 C with old seeds compared to 78 to 86% at 20 to 30 C with new seeds. Germination of common beggars-tick was inhibited at osmotic potential above −0.6 MPa and salt concentrations of 320 mM. Highest germination in common beggars-tick was found under neutral conditions (pH 7); germination decreased sharply under increasing acidity and alkalinity. Emergence decreased as depth of sowing increased, with greatest germination (89 to 91%) occurring when sown at the surface (0 cm) regardless of seed age. No germination was observed when seeds were buried at 10 cm. Results of this study suggest that favorable temperature and soil pH, and adequate moisture in Florida ensures the germination and continued presence of common beggars-tick. Nomenclature: Common beggars-tick, Bidens alba (L.) D.C.

Factors Affecting Germination of Citronmelon (Citrullus lanatus var. citroides)

Abstract Citron melon is a monoecious, hairy annual vine commonly found in citrus orchards, and cotton and peanut fields. Information is not available on the effect of various environmental factors on the germination of citron melon. Laboratory and greenhouse experiments were carried out in 2011 and 2012 to determine the effect of light, temperature, salinity, pH, simulated water stress, and depth of sowing on the germination of citron melon. Citron melon germination was affected by various environmental factors. Highest germination was observed at day/night temperatures of 25/20 to 30/25 C regardless of light conditions. At temperatures below 25 C and beyond 35 C, germination declined and was higher under dark condition than light. Germination decreased as osmotic potential became more negative (−0.3 MPa to −1.5 MPa) and salt concentration increased (50 to 350 mM). No germination was observed at > −0.9 MPa and ≥ 300 mM salt concentrations. However, germination was observed over a broad range of pH (3 to 9) and up to 10-cm sowing depths. Seeds sown at the surface did not germinate but maximum germination (88 to 96%) occurred at 2- to 4-cm depth. The results of this study suggest that citron melon can grow in a wide range of climatic conditions and therefore can persist in Florida because of favorable weather and environmental conditions. Nomenclature: Citronmelon, Citrullus lanatus (Thunb.) Mats & Nakai var. citroides (L.H. Bailey) Mansf., CILAC.

Herbicide tank mixtures for broad-spectrum weed control in Florida citrus

Abstract Weed control in Florida citrus is primarily based on herbicides. Saflufenacil, a POST-applied herbicide is recently registered for broadleaf weed control in citrus. Saflufenacil has very limited grass activity; therefore, it should be tank mixed with graminicides or broad-spectrum herbicides to increase the spectrum of weed control. Greenhouse and field experiments were conducted at two locations (Polk County and Orange County, FL) to evaluate the efficacy and potential antagonism or synergy of saflufenacil and sethoxydim applied alone or tank mixed, and various two- and three-way mixes with glyphosate or pendimethalin. The results suggested that tank mixing saflufenacil and sethoxydim had neither synergistic nor antagonistic effect on broadleaf and grass weed control, respectively. Tank mixing pendimethalin with saflufenacil and sethoxydim improved broadleaf and grass weed control and reduced weed density and biomass, compared with saflufenacil or sethoxydim applied alone or tank mixed at 45 and 60 d after treatment (DAT). Glyphosate tank mixed with saflufenacil and sethoxydim provided > 90% control of broadleaf and grass weeds at 15 DAT, reduced density ≤ 8 plants m−2, and reduced biomass < 95 g m−2 at 60 DAT. Glyphosate applied alone was less effective than it was when tank mixed with saflufenacil and sethoxydim or pendimethalin for broadleaf and grass weed control, indicating an additive effect of tank mixture on glyphosate efficacy. It is concluded that saflufenacil can be tank mixed with sethoxydim for control of broadleaf and grass weeds without antagonism on the efficacy of either herbicide; however, tank mixing saflufenacil and sethoxydim with glyphosate or pendimethalin provided long-term, broad-spectrum weed control in Florida citrus. Nomenclature: Glyphosate; pendimethalin; saflufenacil; sethoxydim; citrus, Citrus spp. Resumen El control de malezas en cítricos en Florida está basado principalmente en herbicidas. Saflufenacil, un herbicida aplicado POST, fue registrado recientemente para el control de malezas de hoja ancha en cítricos. Saflufenacil tiene actividad muy limitada sobre gramíneas; por lo que debe ser mezclado en tanque con graminicidas o herbicidas de amplio espectro para incrementar el espectro de control de malezas. Se realizaron estudios de invernadero y de campo en dos localidades (condados Polk y Orange en Florida) para evaluar la eficacia y el antagonismo o sinergismo potencial de saflufenacil y sethoxydim aplicados solos o en mezcla en tanque, y varias mezclas en dos y tres formas con glyphosate o pendimethalin. Los resultados sugirieron que mezclar en tanque saflufenacil y sethoxydim no tuvo efectos sinérgicos ni antagónicos en el control de malezas de hoja ancha o gramíneas, respectivamente. El mezclar en tanque pendimethalin con saflufenacil y sethoxydim mejoró el control de malezas de hoja ancha y gramíneas y redujo la densidad y biomasa de malezas a 45 y 60 días después del tratamiento (DAT), en comparación con saflufenacil o sethoxydim aplicados individualmente o en mezcla en tanque. Glyphosate mezclado en tanque con saflufenacil y sethoxydim brindó >90% de control de malezas de hoja ancha y gramíneas a 15 DAT, redujo la densidad ≤8 plantas m−2 y redujo la biomasa <95 g m−2 a 60 DAT. Glyphosate aplicado solo fue menos efectivo que cuando se aplicó en mezcla en tanque con saflufenacil y sethoxydim o pendimethalin para el control de malezas de hoja ancha y gramíneas indicando un efecto aditivo de la mezcla en tanque sobre la eficacia de glyphosate. Se concluye que saflufenacil puede ser mezclado en tanque con sethoxydim para el control de malezas de hoja ancha y gramíneas sin causar antagonismo sobre la eficacia de ninguno de estos herbicidas. Sin embargo, el mezclar en tanque saflufenacil y sethoxydim con glyphosate o pendimethalin brindó un control de amplio espectro de malezas de larga duración en cítricos en Florida.

Common Sunflower Seedling Emergence across the U.S. Midwest

Abstract Predictions of weed emergence can be used by practitioners to schedule POST weed management operations. Common sunflower seed from Kansas was used at six Midwestern U.S. sites to examine the variability that 16 climates had on common sunflower emergence. Nonlinear mixed effects models, using a flexible sigmoidal Weibull function that included thermal time, hydrothermal time, and a modified hydrothermal time (with accumulation starting from January 1 of each year), were developed to describe the emergence data. An iterative method was used to select an optimal base temperature (Tb) and base and ceiling soil matric potentials (&psgr;b and &psgr;c) that resulted in a best-fit regional model. The most parsimonious model, based on Akaikes information criterion (AIC), resulted when Tb  =  4.4 C, and &psgr;b  =  −20000 kPa. Deviations among model fits for individual site years indicated a negative relationship (r  =  −0.75; P < 0.001) between the duration of seedling emergence and growing degree days (Tb  =  10 C) from October (fall planting) to March. Thus, seeds exposed to warmer conditions from fall burial to spring emergence had longer emergence periods. Nomenclature: Common sunflower, Helianthus annuus L.

Efficacy of PRE and POST Herbicides for Control of Citron Melon (Citrullus lanatus var. citroides)

Abstract Citron melon is a monoecious and hairy annual vine commonly found in citrus orchards and cotton and peanut fields. There is limited information available on citron melon control with PRE- and POST-applied herbicides in Florida citrus. Experiments were conducted to evaluate the response of citron melon to 11 PRE and 18 POST herbicides under greenhouse conditions. Indaziflam applied PRE at 0.095 kg ai ha−1 resulted in 13% citron melon emergence at 14 d after treatment (DAT). The majority of PRE herbicides did not affect emergence at 14 DAT. Efficacy of PRE herbicides at 21 DAT resulted in > 90% control of citron melon with bromacil, premix formulation of bromacil + diuron, flumioxazin, indaziflam at 0.073 and 0.095, norflurazon, and simazine. Citron melon control was < 30% 21 DAT following PRE-applied diuron, oryzalin, and flazasulfuron. Control of citron melon varied by POST herbicides and growth stage. Regardless of citron melon growth stage, glyphosate, glufosinate, saflufenacil, paraquat, and flumioxazin provided > 90% at 7 and 14 DAT. Carfentrazone, flazasulfuron, imazapic, pyrithiobac-Na, rimsulfuron, trifloxysulfuron, and premix of 2,4-D + glyphosate controlled citron melon at least 90% when applied to two- to four-leaf plants. Control was reduced when application was delayed to the six- to eight-leaf stage. Bentazon and halosulfuron controlled citron melon 11 to 31% regardless of growth stage. Biomass of citron melon at 14 DAT was reduced > 50% in all herbicide treatments except with bentazon and halosulfuron applied at both stages, and dicamba, mesotrione, imazapic, and rimsulfuron applied to six- to eight-leaf citron melon. The results of this study indicate that citron melon can be adequately controlled with several PRE- or POST-applied herbicides; however, research is required to evaluate PRE followed by POST programs or their tank mixtures for season-long control of citron melon under field conditions. Nomenclature: Citron melon, Citrullus lanatus (Thunb.) Mats and Nakai var. citroides (L. H. Bailey) Mansf. CILAC; citrus, Citrus spp.; cotton, Gossypium hirsutum L.; peanut, Arachis hypogaea L. Resumen Citrullus lanatus var. citroides es una enredadera pilosa anual monoica que se encuentra en plantaciones de cítricos y campos de algodón y maní. Hay poca información disponible sobre el control de C. lanatus con herbicidas aplicados PRE y POST en plantaciones de cítricos en Florida. Se realizaron experimentos bajo condiciones de invernadero para evaluar la respuesta de esta maleza a 11 herbicidas PRE y 18 POST. Indaziflam aplicado PRE a 0.095 kg ai ha−1 resultó en 13% de emergencia de C. lanatus 14 días después del tratamiento (DAT). La mayoría de herbicidas PRE no afectaron la emergencia14 DAT. La eficacia de los herbicidas PRE 21 DAT resultó en >90% de control de C. lanatus con bromacil, una formulación pre-mezclada de bromacil + diuron, flumioxazin, indaziflam a 0.073 y 0.095, norflurazon, y simazine. El control de C. lanatus fue <30% 21 DAT después de aplicaciones PRE de diuron, oryzalin y flazasulfuron. El control de esta maleza varió dependiendo de los herbicidas POST y del estado de crecimiento. Independientemente del estado de crecimiento de C. lanatus, glyphosate, glufosinate, saflufenacil, paraquat y flumioxazin brindaron >90% a 7 y 14 DAT. Carfentrazone, flazasulfuron, imazapic, pyrithiobac-Na, rimsulfuron, trifloxysulfuron, y una pre-mezcla de 2,4-D + glyphosate controlaron C. lanatus al menos 90% cuando se aplicaron a plantas con dos a cuatro hojas. El control se redujo cuando la aplicación se atrasó hasta el estado de seis a ocho hojas. Bentazon y halosulfuron controlaron C. lanatus 11 a 31% sin importar el estado de crecimiento. La biomasa de C. lanatus a 14 DAT se redujo >50% en todos los tratamientos de herbicidas excepto con bentazon y halosulfuron aplicados en ambos estados, y dicamba, mezotrione, imazapic y rimsulfuron aplicados en el estado de seis a ocho hojas. Los resultados de este estudio indican que C. lanatus se puede controlar adecuadamente con varios herbicidas aplicados PRE y POST. Sin embargo, se necesita investigación para evaluar el control de C. lanatus a lo largo del ciclo de producción en condiciones de campo usando programas de aplicaciones PRE seguidas por aplicaciones POST o usando mezclas en tanque.