Avaliação da interação de níveis de fertilizantes e misturas de herbicidas na cultura do arroz (Oryza sativa L.) / Evaluation of the interaction of levels of fertilizers and herbicide mixtures in rice cultivation (Oryza sativa L.)

A presente investigação foi realizada com o objetivo de determinar a interação entre os diferentes níveis de fertilização e misturas de herbicidas no cultivo de arroz (Oryza sativa) na área de Babahoyo. Foi utilizada a variedade de arroz INIAP 15. Foi aplicado o delineamento de Parcelas Divididas, cujos tratamentos consistiram em níveis de fertilização, subtratamentos por mistura de herbicidas e três repetições. Para a comparação das médias, foi utilizado o teste de Tukey com significância de 5%. Para estimar os efeitos dos tratamentos e subtratamentos, os dados do índice de toxicidade foram avaliados aos 7 e 14 dias após a aplicação dos herbicidas, controle de plantas daninhas aos 15 e 30 dias após a aplicação dos herbicidas, altura da planta na colheita, número de perfilhos / m2, número de panículas, dias para o florescimento, maturidade fisiológica, comprimento da panícula, grãos por espiga, peso de 1000 grãos, rendimento de grãos e análise econômica. Os resultados mostram que a interação dos níveis de fertilizantes e misturas de herbicidas obteve efeitos positivos na produção da cultura do arroz (Oryza sativa L.), na área de Babahoyo; Aos 7 dias, a toxicidade na cultura era sem danos e aos 14 dias poucos danos foram mostrados; o melhor controle de plantas daninhas foi apresentado com as misturas de Piribenzoxim + 2,4 D amina (1,0 L + 0,7 L) aos 15 e 30 dias após a aplicação dos produtos; Características agronômicas como altura da planta, perfilhos e panículas / m2, comprimento das panículas e grãos por espiga foram influenciadas em suas médias com a aplicação de Nitrogênio (160 kg / ha) + Fósforo P2O5 (40 kg / ha) + Potássio K2O (60 kg / ha); Nos dias para a floração e maturidade fisiológica, todos os tratamentos e subtratamentos responderam da mesma forma porque foi utilizada a variedade Iniap 15; o maior peso de 1000 grãos e produtividade foi apresentado na aplicação de Nitrogênio (160 kg / ha) + Fósforo P2O5 (40 kg / ha) + Potássio K2O (60 kg / ha) e nas misturas de herbicidas aplicadas nos três subtratamentos e. o maior benefício líquido foi alcançado aplicando como fertilizantes Nitrogênio (160 kg / ha) + Fósforo P2O5 (40 kg / ha) + Potássio K2O (60 kg / ha) complementar às misturas herbicidas baseadas em Clomazone + Pyrazosulfuron Etil (1,0 L + 0,35 kg) com $ 662,02 / ha.

Influence of post-treatment irrigation timings and herbicide placement on bermudagrass and goosegrass (Eleusine indica) response to low-dose topramezone and metribuzin programs

Immediate, post-treatment irrigation has been proposed as a method to reduce hybrid bermudagrass [Cynodon dactylon (L.) Pers. x Cynodon transvaalensis Burtt Davy] phytotoxicity from topramezone. Immediate irrigation is impractical since it would take a turfgrass sprayer 10 to 15 minutes to cover an average golf course fairway or athletic field. There is also insufficient evidence regarding how post-treatment irrigation, immediate or otherwise, influences mature goosegrass [Eleusine indica (L.) Gaertn.] control from topramezone or low-dose topramezone plus metribuzin programs. We sought to investigate bermudagrass and E. indica response to immediate, 15-minute, and 30-minute post-treatment irrigation compared to no irrigation following topramezone at 12.3 g ae ha−1, the lowest labeled rate, or topramezone at 6.1 g ha−1 plus metribuzin at 210 g ai ha−1. We also evaluated placement of each herbicide and their combination on soil, foliage, and soil plus foliage to help elucidate the mechanisms involved in differential responses between species and herbicide mixtures. Responses were largely dependent on trial due to bermudagrass injury from high-dose topramezone being nearly eliminated by immediate irrigation in one trial and only slightly affected in another. When post-treatment irrigation was postponed for 15 or 30 minutes, topramezone alone injured bermudagrass unacceptably in both trials. Bermudagrass was injured less by low-dose topramezone plus metribuzin than by high-dose topramezone. All post-treatment irrigation timings reduced E. indica control compared to no post-treatment irrigation. The herbicide placement study suggested that topramezone control of E. indica is highly dependent on foliar uptake and phytotoxicity of both bermudagrass and E. indica is greater from topramezone than metribuzin. Thus, post-treatment irrigation likely reduces topramezone rate load with a concomitant effect on plant phytotoxicity of both species. Metribuzin reduced 21-d cumulative clipping wt and tiller production of plants, and this may be a mechanism by which it reduces foliar white discoloration from topramezone.

Modelling the Effect and Variability of Integrated Weed Management of Phalaris minor in Rice-Wheat Cropping Systems in Northern India

Phalaris minor Retz. (littleseed canarygrass) is the most problematic and herbicide-resistant weed in the rice-wheat cropping system in India. As such, it poses a severe threat to wheat yield and food security. A number of herbicidal and agronomic practices have been identified for the effective control of P. minor. These include crop rotation, crop establishment methods, herbicide spray technology, sowing time, weed seed harvest and effective herbicide mixtures. A population model of P. minor was built based on the life cycle of the species, herbicide resistance mechanisms and the effects of weed control practices. The model simulated the interactions of these factors and provided the best management recommendations for sustainably controlling this noxious weed species. Model results indicate that integration of chemical and non-chemical control methods was the most effective and sustainable strategy. For example, the integration of a happy seeder (a tractor-mounted mulching and sowing machine) with an effective post-emergence herbicide reduced the probability of weed control failure by 32% compared to the scenario with a rotavator and the same herbicide. Similarly, more conventional crop establishment methods such as a rotavator and conventional tillage could be accompanied by pre- or post-emergence applications of herbicide mixtures. Adoption of good herbicide spray technology and weed seed harvest delayed the onset of resistance evolution by up to four years. Furthermore, effective crop rotation such as the inclusion of sugarcane in place of rice in the summer season reduced the risk of resistance evolution by 31% within the 10 year simulation period. In addition to the scenarios using representative parameter values, the variability of model predictions was investigated based on some field experiments. The model provided a powerful tool for promoting Integrated Weed Management and the sustainable use of herbicides. Pragmatic ways of dealing with uncertainty in model prediction are discussed.

Modeling seasonal emergence of Poa annua in urban greenspace

Turfgrasses are perennial components of urban greenspaces found in parks, recreational areas, golf courses, sports fields, and lawns that confer many ecosystem services. A copious seed producer, Poa annua is the most troublesome weed of turfgrass and continually threatens the ecosystem services provided by urban greenspaces. Field research was conducted in Knoxville, TN to better understand environmental conditions triggering P. annua seedling emergence patterns to assist managers with optimally timing interventions—both chemical and non-chemical—for control. Fluctuations in cooling degree day (CDD21C) accumulation accounted for 82% of the variance in yearly cumulative P. annua emergence data collected in a single irrigated sward of hybrid bermudagrass [C. dactylon (L.) Pers. x. C. transvaalensis Burtt-Davy]. However, non-linear models using CDD21C data developed ex post were not able to accurately predict P. annua emergence patterns ex ante. In both years, P. annua emergence changed most rapidly between the 40th and 43rd week of the year when seven-day mean soil temperature and rainfall were 18.9 °C and 12.7 mm, respectively. Future research should explore the efficacy of herbicide mixtures applied when P. annua emergence is most rapidly changing in lieu of developing models to predict when specific emergence thresholds occur.

Evaluation of Pre and Post Emergence Herbicides in Greengram (Vigna radiata L.) during Kharif and Rabi Seasons in the Uplands of Krishna Zone of Andhra Pradesh

Background: Greengram crop is grown round the year as a catch crop in different cropping systems of the uplands of the Krishna Zone of Andhra Pradesh. The practice of application of pre emergence herbicide like pendimethalin is very popular with the farmers for the control of weeds in the uplands, both in kharif and rabi seasons. Further spraying of a selective post emergence herbicide is also practiced by farmers. However, some of the weeds of kharif viz., Phyllanthus maderaspatensis and rabi viz., Chrozophora rottleri could not be controlled with these herbicides due to their late emergence or due to development of partial resistance to these herbicides. Certain new pre (PE) and post emergence (PoE) herbicides viz., pendimethalin 30% + imazethapyr 2%, acifluorfen sodium 16.5% + clodinafop propargyl 8%, fomesafen 11.1% + fluazifop -p-butyl 11.1%, are recommended in crops like soybean and groundnut. However, there is need to test these herbicides available in market for their suitability to control the weeds in greengram. Methods: A field experiment was carried out at Regional Agricultural Research Station, Lam, Guntur, Andhra Pradesh, with an objective to evaluate selected PE and PoE herbicide mixtures in greengram managing the major weeds of greengram grown in vertisols of Krishna Zone of Andhra Pradesh during Kharif and rabi seasons of 2018 under upland conditions. Result: Among the two PE herbicides tested on greengram, pendimethalin 30% + imazethapyr 2% @ 0.75 + 0.05 kg/ha was found to be more effective in reducing the weed density and dry matter compared with pendimethalin 30% @ 0.75 kg/ha. The PoE herbicide mixtures tested viz., fomesafen 11.1% + fluazifop -p-butyl 11.1% @111g/ha, propaquizafop 2.5% + imazethapyr 3.75% @ 50+75 g/ha were on par with imazethapyr 10% @ 50g/ha in controlling the weed population without having any adverse affect on the growth and yield of greengram during kharif and rabi.

A systematic approach for finding herbicide synergies

ABSTRACTCombining herbicides into a double dose is a common approach to overcome the potential for herbicide resistance by weeds. Many herbicide mixtures can be antagonistic and they are rarely synergistic. Here, 24 commercial herbicides, each representing a mode of action were used to create a matrix of all 276 unique combinations to search for new synergies in agar with Arabidopsis thaliana. Herbicides were used at an appropriate sub-lethal dose such that any synergies gave visible growth inhibition. We found five synergies including three new ones, namely mesotrione-norflurazon, mesotrione-clethodim and paraquat-clomazone. All three new synergies were reproducible in soil-grown conditions. Interestingly, all three new combinations included a bleaching herbicide, suggesting synergy might be a class specific phenomenon. We also found that mesotrione-norflurazon and mesotrione-clethodim combinations remained synergistic against lettuce (Lactuca sativa), but not tef (Eragrostis tef). Our study shows that screening herbicide mixtures against A. thaliana is an efficient approach for finding rare herbicide synergies.

Interactions of Clomazone Plus Pendimethalin Mixed with Propanil in Rice

A study was conducted at the Louisiana State University Agricultural Center’s H. Rouse Caffey Rice Research Station in 2017 and 2018 to evaluate the interaction between a pre-package mixture of clomazone plus pendimethalin applied at 0, 760, 1145, or 1540 g ai ha-1 mixed with propanil at 0, 1120, 2240, or 4485 g ai ha-1. A synergistic response occurred when barnyardgrass was treated with all rates of clomazone plus pendimethalin mixed with either rate of propanil evaluated at 56 d after treatment. Unlike barnyardgrass, an antagonistic response occurred for yellow nutsedge control when treated with 760 and 1540 g ha-1 of clomazone plus pendimethalin mixed with 1120 or 2240 g ha-1 of propanil at 28 d after treatment; however, 1145 g ha-1 of clomazone plus pendimethalin mixed with 4485 g ha-1 of propanil resulted in a neutral interaction. At 28 d after treatment, Rice flatsedge treated with for all herbicide mixtures resulted in neutral interactions. The synergism of clomazone plus pendimethalin applied at 1540 g ha—1 mixed with propanil applied at 2240 or 4485 g ha-1 for barnyardgrass control resulted in an increased rough rice yield compared with 760 or 1145 g ha-1 of clomazone plus pendimethalin mixed with propanil applied at 1120 or 2240 g ha-1. These results indicate if barnyardgrass and rice flatsedge are present in a rice field the pre-package mixture of clomazone plus pendimethalin mixed with propanil can be an option for growers. However, if yellow nutsedge infest the area other herbicides may be needed.

Control of Digitaria insularis resistant to glyphosate using a combination of herbicides in coffee farms

Coffee has a significant economic, social, and cultural impact on Brazilian society, generating jobs for thousands of Brazilians. Good management practices such as weed control have direct and indirect benefits on coffee yield and quality. Currently, there is an increase in the infestation rate of Digitaria insularis in coffee plantations due to chemical resistance to glyphosate. In the literature, the study of the combination of glyphosate with different herbicides has been investigated, aiming at improving the efficiency of the control of Digitaria insularis. The objective of this work was to evaluate the efficiency of control of the Digitaria insularis in a coffee farm using a combination of glyphosate with clethodim and phenoxaprope-p-ethyl. Trials were conducted in a commercial coffee farm in southern Minas Gerais in a field with a two-year-old cultivar IAC Catuaí 144. The experiment was conducted under a completely randomized design with five treatments and four replications, totaling 20 experimental plots. Thirty and ninety days after application, the plant numbers were counted and the visual analysis with the use of drones and the digital camera. The results show that the use of glyphosate alone was not efficient in the power of Digitaria insularis. The results show that the herbicide mixtures were efficient in the control.

Cytochrome P450 enzymes inhibitor in the control of Digitaria insularis

ABSTRACT Herbicide interactions can be synergic, additive, or antagonist when mixed in the spray tank. A good example is an association between 2,4-D and graminicides. One hypothesis is that 2,4-D contributes to increasing the Cytochrome P450 activity, which may be one of the causes of antagonism. This study aimed to investigate the use of CYP450 enzymes inhibitor associated with the herbicide mixtures 2,4-D and ACCase inhibitors in vivo on the control of Digitaria insularis. The experiment was performed using a randomized block design in a factorial scheme of 6x2 with four replications. Factor A consisted of untreated check, 2,4-D (1005 g a.e ha-1), clethodim (192 g a.i ha-1) and haloxyfop (62.4 g a.i ha-1), 2,4-D + clethodim (1005 g a.e ha-1+192 g a.i ha-1), and 2,4-D + haloxyfop (1005 g a.e ha-1 +62.4 g a.i ha-1). Factor B represented the presence or absence of malathion (1000 g ha-1) applied two hours before applying the herbicides. A physicochemical test was performed to verify the compatibility of the herbicides in the tank. Malathion application performed two hours before applying the herbicide mixtures (2,4-D and clethodim/haloxyfop) did not provide adequate control of sourgrass, suggesting that CYP450 enzymes inhibited by malathion are not involved in the antagonistic effect between 2,4-D and both graminicides in the management of sourgrass. The 2,4-D + haloxyfop in tank mix demonstrated less efficacy in controlling sourgrass than 2,4-D + clethodim, but both mixtures were incompatible in the tank mix, which may be associated with reduced efficacy in sourgrass management.