Effects Of Preemergence Herbicides Research Articles

Beyond yield: Unveiling farmer perceptions and needs regarding weed management in Bangladesh.

More than 3.5 billion people depend on rice for more than 20% of their daily calories. Globally, Bangladesh is the third largest rice producer. With 171 million people, Bangladesh is also among the top consumers. Local rice production not only affects the country's food security but also influences the global rice trade. A large yield gap has been reported due to weeds. Traditional hand weeding is very costly because of labor shortages resulting from industrialization. Limited data showed a higher yield and profits when using herbicides. However, quantitative data on various aspects of weed management and associated issues representing the country's variable rice ecosystem, which is characterized by 30 agroecological zones, are lacking. We collected data on weed management practices from 865 farmers and 69 agrochemical shops covering all 30 agro-ecological zones (AEZs) through a structured survey. We observed a significant regional variation among various parameters. Approximately 82% of farmers use herbicides, and few rely solely on either manual weeding or herbicides. Pre-emergence herbicides are the predominant. Application procedures are almost the same across the country. Although 40% of farmers had secondary and higher-level education, most depend upon local sellers' suggestions rather than reading the product label regarding the dose. Few farmers consider herbicides hazardous, and respondents rarely perceive any environmental impact. Pyrazosulfuron ethyl (35%) and acetochlor-containing bensulfuron methyl (27%) are the most-used chemical species. Approximately 45% of farmers observed that herbicides suppress early seedling growth. Additional fertilizer is required to compensate for this. Multiple weed species that are difficult to control through presently used herbicides were noted in all AEZs. Around 64% of farmers observed that herbicide application contributes to higher yields as a function of timely weeding. Cost comparisons showed that high labor prices will make rice cropping unprofitable in most parts of the country if herbicides are eliminated. Clear adverse effects of pre-emergence herbicides on early crop growth implied the potential benefits of broad-spectrum herbicide-tolerant genetically engineered (GE) rice to sustain the country's food security. Additionally, such GE rice could incentivize the adoption of alternate wet and dry irrigation methods, leading to water and cost savings.

Effect of pre-emergence herbicides on weed dynamics and productivity of soybean [Glycine max (L.) Merill

Effect of pre-emergence herbicides on weed dynamics and productivity of soybean [Glycine max (L.) Merill

Effects of Pre-Emergence Herbicides on Weed Control and Yield of Safflower (Carthamus tinctorius L.) in Central Italy

Safflower is a multipurpose crop with several uses that can offer benefits to rainfed cereal-based cropping systems due to its tolerance to cold, drought, salinity, and its reduced need for agricultural inputs. Safflower requires good weed control for optimum yields because it is a very poor competitor with weeds, especially at the early growth stage, but registered pre-emergence herbicides are not available. This research investigated the effects of several pre-emergence herbicides on weed control and the yield of safflower in central Italy, through two field experiments in 2019 and 2020. Aclonifen, metazachlor, s-metolachlor, propyzamide, and metribuzin were applied as pre-emergence herbicides. The main weeds were the following: Papaver rhoeas L., Conyza canadensis (L.) Cronq., and Ammi majus L. in experiment 1, and wild sunflower (Helianthus annuus L.) in experiment 2. Metazachlor and metribuzin gave the highest phytotoxicity on safflower in both experiments, with values ranging from 48% to 75% and from 30% to 75% (in a scale of 0–100%), respectively, and seem to be not advisable as pre-emergence herbicides. Aclonifen, s-metolachlor, and propyzamide can be considered selective and safe to the safflower, showing the lowest values of phytotoxicity that ranged from 0 to 10%. Metazachlor and s-metolachlor gave the highest total weed control with values of 92% and 97%, respectively.

Effect of Chemical and Hand weeding Control Methods on Growth Yield Components and Yield of Field Pea in Bale Highlands, Southeastern Ethiopia

Afield experiment was conducted during bona season of 2019/2020 and 2021/2022 at two location Agarfa sub-site and Sinana on station to evaluate the integrated effects of pre-emergence herbicides and hand-weeding on weed control, yield components, yield, and their economic feasibility for cost effective weed control in field pea. The treatments consisted of three dual gold rates (1, 2 and 3 liter per hectares) and three times (0, 1and 2 times hand weeding). The experiment was laid out in a factorial arrangement of RBCD with three replications. Results indicated that Dual-gold 2 liter per hectare supplemented with hand weeding at 25-30 days after crop emergence resulted in the highest grain yield and economic benefit. However, in case labor is constraint and Pre-emergence herbicide is timely available, pre emergence application of Dual-gold 2 liter per hectare should be the alternative to prevent the yield loss and to ensure maximum net benefit for the producers. Thus, the result of this study, it can be tentatively concluded that herbicides application is an integral part of farmer’s pulse crop management in modern agricultural systems.

Evaluation of pre-emergence herbicides for weed management and rice yield in direct-seeded rice in Cambodian lowland ecosystems

Poor weed management in direct-seeded rice (DSR) at crop establishment stage has led to the need to explore different pre-emergence herbicides to reduce weed biomass and increase DSR yield in Cambodian lowland ecosystems. This study evaluated weed and yield responses to pre-emergence herbicides (pendimethalin, pretilachlor, butachlor, oxadiazon and no application as the control) under different weed management options during the 2018 and 2019 early wet seasons in farmers’ rice fields. All pre-emergence herbicides reduced weed flora and pendimethalin was most effective in controlling the population of mainly grassy weeds. Pendimethalin significantly reduced weed dry biomass by 36.2% (21.3 ​g ​m−2) in 2018 compared with the untreated control. In 2019, weed dry biomass was significantly reduced by 46% (17.9 ​g ​m−2) with butachlor compared with the untreated plot. Pendimethalin increased toxicity in rice plants, which decreased SPAD (leaf greenness) by 44.8% and tiller numbers by 39.3% at 7 days after herbicide application (DAPH) compared with butachlor, but plants recovered from pendimethalin toxicity at 14 DAPH. In 2018, oxadiazon herbicide significantly increased grain yield by 61% (4.6 ​t ​ha −1) compared with the untreated control, but oxadiazon produced similar grain yields as pendimethalin. In 2019, there was no significant effect of pre-emergence herbicides on yield but butachlor produced the highest rice yield (3.2 ​t ​ha−1) followed by pendimethalin (2.8 ​t ​ha−1) and oxadiazon (2.7 ​t ​ha−1). Our study demonstrated that pre-emergent herbicides function differently under varying soil-water conditions in 2018 and 2019, therefore rice growers can use butachlor to control weeds in dryer soil conditions and potentially use pendimethalin to control weeds in good soil moisture conditions. This information is crucial and safe in developing appropriate strategies to manage weeds and enhancing DSR productivity in lowland ecosystems.

Oxyfluorfen and Linuron: Residual Effect of Pre-Emergence Herbicides in Three Tropical Soils

Knowledge about the residual effect of herbicides is important in order to increase agronomic efficacy and reduce environmental problems. Therefore, the objective of this study was to evaluate the residual effect of oxyfluorfen and linuron in three soils. Pots of 0.35 dm3 were filled with three Brazilian soils: Ultisol, Oxisol, and Inceptisol. Then, the herbicides were applied at different times at 0, 15, 30, 45, 60, 90, 120, 150, 180, and 200 days and the bioindicator species of linuron and oxyfluorfen were sown. Then, the injury was evaluated at 7, 14, and 21 days after emergence (DAE) to find the half-life of the herbicide residue level (RL50) and the dose of herbicide that provides a 50% reduction in dry matter (GR50). In the soil with oxyfluorfen application, the RL50 at 21 DAE was 59, 57, and 51 days and GR50 was 49, 47, and 31 days for Ultisol, Oxisol, and Inceptisol, respectively. Soils with linuron application had RL50 of 75, 92, and 149 days and GR50 of 52, 48, and 120 days for Ultisol, Oxisol, and Inceptisol, respectively. The higher organic matter and clay content of Ultisol compared to Oxisol and Inceptisol resulted in a lower residual effect of linuron. There was little difference between soil type and the residual effect of oxyfluorfen, which may be related to the physicochemical characteristics of the molecule.

Effect of pre emergence herbicides on weed dynamics and production potential of rice (Oryza sativa) under SRI

Effect of pre emergence herbicides on weed dynamics and production potential of rice (Oryza sativa) under SRI

Effects of Herbicides on the Microbial Community and Urease Activity in the Rhizosphere Soil of Maize at Maturity Stage

Studying the effects of herbicides on microbial community and urease activity in the rhizosphere soil of maize is helpful to clarify the mechanisms herbicides used to affect soil microbial environment. In this research, four common preemergence maize specific herbicides, nicosulfuron+atrazine (A1), alachlor+acetochlor+atrazine (A2), propisochlor+atrazine (A3), and acetochlor+atrazine (A4), were selected to use in a pot trial. A preemergence herbicide nonspecific for maize, dinitraniline (A0), was used as the positive control, whereas water instead of herbicide was considered as the negative control (CK). At the maturity stage, the microbial communities and urease activity in the 0‐20 cm, 20‐40 cm, and 40‐60 cm rhizosphere soils of maize were analyzed. Results showed that A0 dramatically suppressed maize growth, with no grain got finally, while A1 displayed the weakest effect. The tested herbicides affected the microbial community in the 0‐20 cm layer greater than in the 20‐60 cm ones, with A1 displaying the greatest effect. In the 0‐20 cm soil, A1 largely reduced the relative abundance of the top three dominant genera, Prevotella, Barnesiella, and Lactobacillus in the CK soil, by 99.0%, 98.7%, and 79.2%, and made Pseudomonas, Gemmatimonas, and Sphingomonas became the new dominant genera, while A2 and A3 displayed similar but slighter effects. All herbicides dramatically reduced the relative abundance of the top one dominant fungal phylum (Ascomycota) and genus (Diatrype) in the CK soil, from 45% to 5.2%‐7.9% and 42% to 2.1%‐3.2%. A0 dramatically dropped the urease activity in the 0‐60 cm soils, by 30.5%‐33.1%, whereas A1‐A4 displayed an unsignificant effect. In conclusion, A1 is a suitable herbicide for maize. Both the bacterial community and urease activity in the 0‐20 cm rhizosphere soil are suitable indices to evaluate the effects of preemergence herbicides on maize growth and soil microbial environment.

Effects of preemergence herbicides on establishment of little bluestem and sideoats grama golf course rough

AbstractNative warm‐season grass (NWSG) roughs provide environmental and aesthetic value to golf courses; however, weed competition is a constraint during establishment. This research evaluated the effects of common turfgrass preemergence herbicides on establishment of newly seeded 1:1 mixture of little bluestem [Schizachyrium scoparium (Michx.) Nash] and sideoats grama [Bouteloua curtipendula (Michx.) Torr.] (14.3 lb total seed acre−1) rough. Herbicides applied immediately after drill‐seeding included: atrazine (1.0 lb a.i. acre−1), dimethenamid‐P (1.5 lb acre−1), dithiopyr (0.38 lb acre−1), imazapic (0.06 lb acre−1), indaziflam (0.029 lb acre−1), isoxaben (1.0 lb acre−1), S‐metolachlor (2.48 lb acre−1), oxadiazon (4.0 lb acre−1), pendimethalin (1.47 lb acre−1), prodiamine (0.75 lb acre−1), and simazine (1.0 lb acre−1). Effects upon NWSG plant density and biomass, as well as smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.] control, were evaluated in 2017 and 2018. Across years, imazapic, dimethenamid, oxadiazon, and metolachlor controlled crabgrass >90%. In 2017, little bluestem plant density assessed 4 months after treatment was 2 to 13 times greater in imazapic‐treated plots than all other treatments except for those treated with isoxaben and simazine. Application of imazapic resulted in greater little bluestem aboveground biomass than all other herbicide treatments, except simazine, in 2017. In 2018, imazapic resulted in greater little bluestem plant density than the untreated control, atrazine, prodiamine, oxadiazon, isoxaben, or simazine. Although it was a minor component of the sward, sideoats grama was generally tolerant of imazapic. Imazapic application during seeded establishment of little bluestem and sideoats grama golf course rough provides acceptable crop tolerance and smooth crabgrass control.

Effect of Different Herbicides, Plant Extracts and Mulches on Yield and Yield Components of Maize

ABSTRACT: To examine the effect of pre emergence herbicides, plant extracts and mulches on yield and yield components of maize, a field experiment was carried out at New Developmental Farm, The University of Agriculture Peshawar-Pakistan during summer crop season 2016. Maize variety “Azam” was sown in Randomized Complete Block (RCB) design having four replications and ten treatments i.e. hand weeding, Dual Gold 960 EC (S-metolachlor 1 L ha-1), Stomp 330 EC (pendimethaline 2.5 L ha-1), atrazine 1.25 L ha-1, Eucalyptus camaldulensis L. extract (125 g L-1), Ammi visnaga L. extract (125 g L-1), black plastic mulch, wheat straw mulch, saw dust mulch and weedy check. The data revealed that hand weeding and herbicides significantly affected the weed density (m-2), weeds biomass (kg ha-1), plant height (cm), kernels weight (g), number of kernels ear-1, biological yield (kg ha-1) and grain yield (kg ha-1). All the significant parameters of crop were comparable among the hand weeding, atrazine, S-metolachlor and pendimethaline treated plots. However, atrazine and S-metolachlor proved to be the most economical herbicides giving maximum yield (4636.4 and 4562.8 kg ha-1), respectively. Among plant extracts, E. camaldulensis showed satisfactory results in suppressing weeds and enhancing yield of maize i.e. (3441.6 kg ha-1). Hence, the use of herbicides (atrazine and S-metolachlor) at the recommended rates and hand weeding is recommended for effective weed control and ultimately high yield of maize crop.

Integrated weed management in chickpea (Cicer arietinum L.)

The poor competition ability of chickpea opens the door for weed to cause a serious yield loss. The experimental field is conducted to evaluate the integrated effects of pre-emergence herbicides an...

Preemergence Herbicide Effects on Establishment and Tensile Strength of Sprigged Hybrid Bermudagrass

Core Ideas Preemergence herbicides may increase grow‐in time for hybrid bermudagrass sprigs. Preemergence herbicide treatments did not reduce sod tensile strength. Preemergence herbicides are viable options for weed control during establishment. Preemergence herbicides often negatively affect establishment of sprigged hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy). However, limited research has quantified the effects of preemergence herbicides on establishment and tensile strength of warm‐season turfgrass species commonly grown as sod in the southeastern United States. Field research was conducted at Mississippi State University in 2016 and 2017 to evaluate the effects of atrazine, atrazine + S‐metolachlor, dithiopyr, flumioxazin, indaziflam, liquid‐ and granular‐applied oxadiazon, S‐metolachlor, pendimethalin, prodiamine, and simazine on grow‐in time and tensile strength of newly sprigged ‘Latitude 36’ hybrid bermudagrass. Plots (4.65 m2) were sprigged at a rate of 44 m3 ha−1 (468 US bushels ac−1), and preemergence herbicide treatments were applied at the recommended labeled rates 1 d after planting. Dithiopyr, flumioxazin, S‐metolachlor, and indaziflam increased days to reach 50% hybrid bermudagrass cover in both 2016 and 2017. Normalized difference vegetative index and relative chlorophyll index were similarly affected. No herbicide treatments reduced sod tensile strength in either year; however, prodiamine, pendimethalin, dithiopyr, flumioxazin, and S‐metolachlor unexpectedly increased sod tensile strength in 2017.

Studies on tolerance of chickpea to some pre and post-emergence herbicides

Herbicides application is an integral part of farmer’s crop management in modern agricultural systems. Weeds always cause serious losses in legumes due to poor competition ability. In order to quantify the tolerance of chickpea against some pre and post-emergence herbicides, a pot study was carried out in the department of Weed science, The University of Agriculture, Peshawar Pakistan during 2012-13 and 2013-14. The pre emergence herbicides includes pendimethalin and s-metolachlor while, the post emergence herbicides comprised of Clodinafop-propargyl, fenoxaprop-p-ethyl and di-methyl urea. The chickpea variety Karak-I was sown in the pots and the trial was arranged in CR Design repeated three times. During the investigation data were recorded on different growth parameters of chickpea plants including both aerial and underground parts. The results revealed the all treatments had a significant effect on all the examined parameters of chickpea except nodule fresh and dry biomasses. However, the toxic effect of pre emergence herbicides on chickpea was significantly higher as compared to post emergence herbicides. The minimum number of nodule plant-1 (17.83), plant height (50.50cm), and seed protein (14.13%) was recorded in Pendimethalin treated pots. However, the highest seed protein content of 21.75 and 21.15 % were recorded for control and fenoxaprop-p-ethyl treatments respectively. Thus, it is concluded from the present data that chickpea has less tolerance for pre emergence herbicides pendimethalin and S-metolachlor as compared to post-emergence herbicides so farmers are advised to give preference to post emergence herbicides instead of a pre emergence while controlling weeds in chickpea through chemicals.

Assessment of Integrated Weed Management Practices on Weed Dynamics, Yield Components and Yield of Faba bean (Vicia faba L.) in Eastern Ethiopia

The experiment was conducted to assess the integrated effects of pre-emergence herbicides and hand-weeding on weed control, yield components, yield, and their economic feasibility for cost effective weed control in faba bean. The experiment consisted of 12 treatments viz. pre-emergence s-metolachlor (1.0, 1.5 and 2.0 kg ha-1) and pendimethalin (1.0, 1.25 and 1.5 kg ha-1), each at three rates metolachlor, s-metolachlor + one-hand-weeding, pendimethalin + one-hand-weeding, two-hand-weeding, complete weed free and weedy checks arranged. The weed flora consisted of broadleaved and sedge with the relative densities of 81.02 and 18.98 % at Haramaya district, and 80.83% and 19.17%, at Gurawa district, respectively. Application of s-metolachlor and pendimethalin 1.0 kg ha-1 each supplemented with hand weeding 5 WAE significantly (p ≤0.01) affected the broadleaved weeds, sedges and weed dry weight at both sites. S-metolachlor 1.0 kg ha-1 supplemented with hand weeding 5 WAE gave the lowest total number of weeds (8.29 m-2) following the weed free check. Higher grain yield (3555.8 kg ha-1) was produced with s-metolachlor 1.0 kg ha-1 supplemented with one-hand-weeding 5 WAE following complete weed-free at Gurawa. The benefit gained from s-metolachlor and pendimethalin at 1.0 kg ha-1 each supplemented with one hand weeding 5 WAE were greater than the value recorded from the weedy check by 216% and 198 %, respectively. S-metolachlor 1.0 kg ha-1 supplemented with hand weeding 5 WAE treatment resulted in the highest grain yield and economic benefit. However, in case labour is constraint and s-metolachlor herbicide is timely available, pre emergence application of s-metolachlor at 2.0 kg ha-1 should be the alternative to preclude the yield loss and to ensure maximum benefit.

Evaluation of the Efficacy of Some Pre-Emergence Herbicides in Cotton (<i>Gossypium Spp.</i>) in Northern Ghana

A field experiment was conducted at the Savanna Agricultural Research Institute to investigate the effects of pre-emergence herbicides for weed control in cotton during the 2014 and 2015 cropping seasons. The study determined the effects of different rates of three novel cotton herbicides with different formulations on weeds, yield components and yield of seed cotton, applied as pre-emergence. The treatments were laid out in randomized complete block design with four replications and consisted of Diflufenican + Flufenicent and Diflufenican + Flufenicent + Flurtamone as 500SC formulations of each and applied at the rate of 0.3, 0.4, 0.6, and 0.8 l/ha, whilst Diflufenican + Flufenicent + Flurtamone as 200SC formulation was applied at 0.4, 0.5, 0.8, and 1.0L/ha. A reference herbicide + product with active ingredients Promotrin + Metolachlor applied at 3.0l /ha and untreated weedy and weed free checks were included. Results showed that. Diflufenican + Flufenicent + as 200SC applied at 0.8 l/ha gave the lowest weed dry weight (65.0 g/m2) similar to the reference herbicide (189.4 g/m2) and Diflufenican + Flufenicent + Flurtamone as 200SC applied at 0.8 l/ha (144.8 g/m2), whilst weedy check gave highest (548.7 kg/m2). Consequently, Diflufenican+ Flufenicent applied at 0.8 l/ha gave significantly (p<0.05) the highest number of bolls and number of opened bolls than the reference herbicide; but similar to weed free. Diflufenican + Flufenicent +Flurtamone as 500SC, applied at 1.0 l/ha supported tallest plants similar to Diflufenican + Flufenicent + Flurtamone as 200SC at 0.4 and 0.6 l/ha and Diflufenican + Flufenicent as 500SC applied at 0.6 and 0.8 l/ha and better than the reference herbicide. Diflufenican+ Flufenicent as 500SC applied at 0.8L/ha (81.3 %), Diflufenican + Flufenicent + Flurtamone as 500SC at 0.8 l/ha (78.7 %) and the reference herbicide (76.3 %) did better (90 %) than weed free. Generally, early control of weeds with the tested herbicides using 0.4 to 1.0 l/ha minimized weed growth and supported high seed cotton yields.

Impact of fluopyram fungicide and preemergence herbicides on soybean injury, population, sudden death syndrome, and yield

Field experiments were conducted in Indiana and Iowa in 2014 and 2015 to examine the effect of preemergence herbicides and fluopyram seed treatment on soybean (Glycine max (L.) Merr.) injury, plant population, sudden death syndrome (SDS; Fusarium virguliforme O'Donnell & T. Aoki), and yield. Sulfentrazone + cloransulam-methyl + S-metolachlor and flumioxazin + chlorimuron ethyl + S-metolachlor herbicides resulted in higher phytotoxicity at growth stage VC-V1 compared to a non-treated control. Phytotoxicity due to preemergence herbicide was rarely observed at V4. Seed treated with fluopyram resulted in higher phytotoxicity at VC-V1 than seed without fluopyram, regardless of preemergence herbicide treatment. The combination of preemergence herbicide and fluopyram did not increase the severity of soybean injury in any year or location compared to either applied alone. Preemergence herbicide treatment reduced plant population in Indiana in 2014 and Iowa in 2015 compared to the non-treated control, but did not affect yield. Fluopyram seed treatment reduced foliar symptoms of SDS by over 70% and increased yield up to 12% in Indiana, but had no effect on SDS or yield in Iowa. These results indicate that while injury can occur with both preemergence herbicides and fluopyram-treated seed, phytotoxicity is not more severe when both pesticides are used together, and yield is not reduced by their use. Farmers should continue to use preemergence herbicide programs if they treat their seed with fluopyram to manage SDS, and use production practices that minimize the risk of preemergence herbicide injury in soybean.

Influence of Integrated Weed Management Practices on Weed Dynamics, Yield Components and Yield of Faba bean (Vicia faba L.) in Eastern Ethiopia

The experiment was conducted to assess the integrated effects of pre-emergence herbicides and hand-weeding on weed control, yield components and yield of Faba bean to assess their economic feasibility for cost effective weed control in Faba bean. The experiment consisted of 12 treatments viz. pre emergence S-metolachlor and Pendimethalin each at three rates S-metolachlor+one-hand-weeding, pendimethalin+one-hand-weeding, two-handweeding, complete weed free and weedy checks arranged in randomized complete block design with three replications. The weed flora consisted of broadleaved and sedge with the relative densities of 81.02 and 18.98% at Haramaya, and 80.83% and 19.17%, at Gurawa, respectively. Application of S-metolachlor and Pendimethalin 1.0 kg ha-1 each supplemented with hand weeding 5 WAE significantly (p ≤ 0.01) affected the broadleaved weeds, sedges and weed dry weight at both sites. S-metolachlor 1.0 kg ha-1 supplemented with hand weeding 5 WAE gave the lowest total number of weeds (8.29 m-2) following the weed free check. Higher grain yield (3555.8 kg ha-1) was produced with S-metolachlor 1.0 kg ha-1 supplemented with one-hand-weeding 5 WAE following complete weed-free at Gurawa. The benefit gained from S-metolachlor and Pendimethalin at 1.0 kg ha-1 each supplemented with one hand weeding 5 WAE were greater than the value recorded from the weedy check by 216% and 198%, respectively. S-metolachlor 1.0 kg ha-1 supplemented with hand weeding 5 WAE treatment resulted in the highest grain yield and economic benefit. However, in case labour is constraint and S-metolachlor herbicide is timely available, pre emergence application of s-metolachlor at 2.0 kg ha-1 should be the alternative to preclude the yield loss and to ensure maximum benefit.

Effects of Preemergence Herbicides on Bell Pepper, Crop Injury, and Weed Management in Irrigated Chilean Fields

Bell pepper is an economically important vegetable crop that is often impaired by weeds. Management of weeds in bell pepper is required to minimize yield loss because this crop does not tolerate weed competition. Several herbicides have been reported as selective for bell pepper, but research supporting their use for weed control in this crop is limited. Several herbicides were screened in a greenhouse to assess effects on plant biomass, and eight were selected that appeared to be safe for bell pepper. These herbicides, in addition to oxadiargyl, were then evaluated at two different Chilean locations, using different application timings. We measured the effects on plant injury, fruit yield, and the need for additional hand weeding on transplanted bell peppers. The herbicides clomazone, napropamide, pendimethalin, andS-metolachlor caused minimal foliar chlorosis and necrosis but did not affect fruit yield at either location. Pretransplant-incorporated application (PTI) caused no effect on fruit yield from the herbicides evaluated, whereas applications 2 wk (POST2) and 8 wk (POST8) after transplanting reduced fruit yield significantly. For weed management, the best combination was PTI + POST2 + POST8, which reduced the hand-weeding time by 30% compared to the control, at both locations. Based on our results, clomazone, pendimethalin, andS-metolachlor were the most effective treatments applied after transplanting, whereas all herbicides tested were selective for bell pepper when applied and incorporated before transplanting. Results presented here provide new insight into herbicides that can be used to manage weeds in bell pepper and shows that timing of herbicide application is critical to prevent injury to this crop.

Effect of pre-emergence herbicides and timing of soil saturation on the control of six major rice weeds and their phytotoxic effects on rice seedlings

The study evaluated the effects of pre-emergence herbicides and their rates [oxadiazon (0.5 and 1 kg ai ha−1), pendimethalin (1 and 2 kg ai ha−1), and pretilachlor with safener (0.6 kg ai ha−1)], and time of soil saturation establishment after herbicide application [1, 3, 5, and 7 days after spray (DAS)] in controlling the six major rice weeds, and their phytotoxic effects on rice seedling growth. All herbicides provided 100% control of Echinochloa colona, Echinochloa crus-galli, Leptochloa chinensis, Cyperus iria, and Amaranthus spinosus. Murdannia nudiflora was 100% controlled by oxadiazon and pretilachlor with safener, but poorly controlled (22–75%) by pendimethalin. Pendimethalin at 2 kg ai ha−1 was more effective than at 1 kg ai ha−1 in reducing the biomass of the stem, leaf, and root of M. nudiflora irrespective of timing of soil saturation. Rice plant height was reduced to a maximum (77–96%) by pendimethalin at 2.0 kg ai ha−1 followed by oxadiazon at 1.0 kg ai ha−1 (38–70%) compared to the non-treated control. In contrast, the tallest rice plants were observed in the non-treated control and those treated with pretilachlor with safener which had 80–100% rice plant survival. The lowest rice plant survival of 0, 6, 7, and 16% was found in the soil applied with pendimethalin at 2 kg ai ha−1 and saturated at 1, 3, 5, and 7 DAS, respectively, which was followed by oxadiazon at 1 kg ai ha−1. All herbicides except pretilachlor with safener reduced SPAD values with early soil saturation, which improved with delay in soil saturation timing. Pendimethalin at 2 kg ai ha−1 reduced the SPAD values of rice plants by 100–164% relative to the non-treated control and produced the highest phytotoxicity symptoms. Pendimethalin also reduced rice shoot biomass more than oxadiazon, which was compounded by early soil saturation after herbicide application. Pretilachlor with safener was the only herbicide that exhibited low phytotoxic symptoms on rice plants and did not reduce leaf, stem, root, and shoot biomass of rice. Percent reduction in rice leaf, stem, root, and shoot biomass by the different herbicides was in the order of pendimethalin 2 > oxadiazon 1 > pendimethalin 1 > oxadiazon 0.5 > pretilachlor with safener 0.6 kg ai ha−1. Each herbicide treatment reduced rice growth parameters as soil saturation was delayed in the order of 1 DAS > 3 DAS > 5 DAS > 7 DAS. The study suggests that soil water content and herbicide rates are important factors in influencing herbicide phytotoxicity in rice. The application of herbicides should be avoided when the soil is too wet, and irrigation should be delayed at least one week after herbicide application.

Effect of Pre-Emergence Herbicides on Vegetative and Floral Parameters in Chrysanthemum

Effect of Pre-Emergence Herbicides on Vegetative and Floral Parameters in Chrysanthemum