Phalaris Minor Research Articles

Sensitivity of littleseed canary grass populations from Punjab, India, to clodinafop‐propargyl and isoproturon

AbstractLittleseed canary grass (Phalaris minor Retz.) is one of the most prevalent and troublesome annual grass weed species in wheat across the Indo‐Gangetic plains (IGP) of India, including Punjab. Littleseed canary grass has evolved resistance to different herbicide sites of action in the IGP region. A targeted field survey was conducted in 2018 and 2019 for seed collection of littleseed canary grass populations (total 94) across different districts of Punjab state prior to wheat harvest. The main objective of this research was to characterize the sensitivity response of collected littleseed canary grass populations to clodinafop‐propargyl (CP) and isoproturon (IPU) herbicides in whole‐plant dose‐response assays. Among all tested populations, 68 were found to be highly sensitive to CP, whereas all 94 populations were sensitive to IPU. Based on a 50% reduction in shoot dry biomass (GR50 values) and estimated sensitivity index (SI), 26 populations exhibited reduced sensitivity (SI of 2.2–4.4) to CP herbicide. The results also revealed that the littleseed canary grass populations with reduced sensitivity (SI ≥ 2.2) to CP had high sensitivity to IPU herbicide. Overall, these results suggested a high prevalence of littleseed canary grass populations with reduced sensitivity to CP herbicide in Punjab state. Diversified weed management strategies, including the use of alternative herbicides (both preemergence and postemergence), cultural (no‐till drill for wheat sowing and narrow row spacing), and mechanical (cutting of littleseed canary grass panicles prior to wheat harvest) practices should be adopted to control littleseed canary grass populations with reduced sensitivity to CP.

Effects of Various Nitrogen Regimes on the Ability of Rapeseed (Brassica napus L.) to Suppress Littleseed Canarygrass (Phalaris minor Retz.)

Using crops to control invasive weeds is an important approach for the long-term management of invasive species in agroecosystems. Nitrogen application can improve the yield and quality of crops, but may shift interactions of invasive weeds and crops, potentially affecting grass control ability. To explore the yield of a crop and its control efficacy of invasive weed under different nitrogen conditions, we studied the competitive effects of the high-value crop rapeseed (Brassica napus L.) on growth and photosynthetic characteristics of invasive species littleseed canarygrass in the field experiments. The results showed that the rapeseed yield and its control efficacy on littleseed canarygrass were significantly affected (p < 0.05) under different N regimes, and the control efficacy of littleseed canarygrass by rapeseed increased first and then decreased with the increase of basal nitrogen rates, while increasing topdressing N rates increased control efficacy of littleseed canarygrass by rapeseed. In fact, yield and weed control efficacy of rapeseed was most ideal when both basal and topdressing N was 90 kg·ha−1. We also found that N significantly impacted the competitive ability of rapeseed toward littleseed canarygrass, and rapeseed had the highest competitive ability when both basal and topdressing N was 90 kg·ha−1. With the increase of basal nitrogen rates, competitive balance index (CB) of rapeseed increased initially but decreased beyond an optimal level. CB continually increased with increasing topdressing N rates. Our research also showed level and period of N application had a significant effect (p < 0.01) on the photosynthetic rate (Pn) and chlorophyll content (Chl) of both rapeseed and littleseed canarygrass. Under the same N application regime, the Pn and Chl of littleseed canarygrass were higher than that of rapeseed in December, while the Pn and Chl of rapeseed was higher than that of littleseed canarygrass in February. Our study indicated that photosynthetic characteristics of rapeseed and littleseed canarygrass in different growth stages differ in their sensitivity to N regimes, creating a dynamic competitive relationship. Together, our results demonstrated that optimal application of fertilizer N could help rapeseed produce higher yields and greater weed control efficacy, suggesting that future modeling or experimental studies on utilizing crops to control invasive weeds should carefully consider both timing and placement of N.

Phalaris minor (littleseed canarygrass)

Phalaris minor (littleseed canarygrass)

The Leaching of Atrazine and Plant Species Sensitivity to Atrazine using Bioassays and Chemical Analyses

ABSTRACT Atrazine, one of the most frequently applied herbicides in the world, is highly persistent, and likely to contaminate runoff and groundwater resources, determined by bioassay and chemical analyses. In the present research the two following experiments were conducted in Mazandaran Province, Iran. 1) The sensitivity of eight plant species (canola, soybean, ryegrass, wild oat, wheat, littleseed canarygrass, redroot pigweed, and corn) to atrazine residues in the laboratory of the Qaemshahr Campus of the Islamic Azad University in 2019 was determined. Bioassay and GR50 index were used to differentiate species. 2) The leaching front of atrazine in the laboratory of Mazandaran University of Medical Sciences was determined. Soil samples were collected from a 10-hectare-farm of Baykola Agricultural Research Station. The method of undisturbed soil columns was used to study atrazine leaching at three levels including control, usual dose (1.25 kg. ha−1), and high dose (2.5 kg. ha−1). The treatments were injected into soil columns inside 32-cm-high PVC pipes and after three days, 2-cm segments of the soil columns were exposed to bioassay and chemical analyses, simultaneously. In the first experiment, plants response to atrazine residues were different. Canola and corn were the most susceptible and tolerant crop species, respectively. The tolerance of other plant species to total residue, using GR50 index, was according to the following order: canola < soybean < ryegrass < wild oat < wheat < littleseed canarygrass < redroot pigweed < corn. According to the bioassay test, at the high dose of atrazine, all traits were negatively affected, and the root weight and the ratio of root to shoot weight had the highest and the lowest decrease (28% and 12% relative to control), respectively. The simultaneous investigation of canola seedling weight and atrazine concentration, at different soil depths, revealed that atrazine penetrated to the 10-cm depth, which is attributed to higher organic matter and clay content. Canola was identified as a suitable plant for atrazine bioassay. Due to the depths of weed seed distribution and leaching front of atrazine in this experiment (on average, 10 cm), the contamination of weed seed lot with herbicides can be high.

Predicting Seedling Emergence of Three Canarygrass (Phalaris) Species under Semi-Arid Conditions Using Parametric and Non-Parametric Models

The Phalaris genus includes annual weed species such as short-spiked canarygrass (Phalaris brachystachys Link.), little-seed canarygrass (Phalaris minor Retz.) and hood canarygrass (Phalaris paradoxa L.), which are especially problematic in Spain; as such, there is a need to develop models to predict the timing of their emergence. Field experiments were conducted at two different locations during two (2006/07 and 2007/08) and three (from 2005/06 to 2007/08) growing seasons. In both locations, 500 seeds of each Phalaris species were sown each growing season, simulating rain-fed cereal field conditions. In addition, the models were validated with three, four and eight independent experiments for P. brachystachys, P. minor and P. paradoxa, respectively. The emergence period of the three Phalaris species lasted between 31 and 48 days after sowing (DAS), showing two main flushes. The three cardinal points for parametric and non-parametric models were established to be between −1 °C and 1 °C for base temperature, between 9.8 °C and 11.8 °C for optimal temperature and between 21.2 °C and 23.4 °C for ceiling temperature; base water potential was estimated to be between −1 and −1.1 MPa. Both parametric and non-parametric models obtained similar results and were successfully validated in 12 out of 15 independent experiments.

Culturable microbial diversity in the rhizosphere of different biotypes under variable salinity

The microbial diversity in the rhizosphere of different biotypes is influenced by different factors like plant species, root exudates and soil environment. Culturable microbial diversity in the rhizosphere of six biotypes (Chenopodium murale (CM), Spergula arvensis (SA), Launaea nudicaulis (LN), Brassica juncea (BJ), Phalaris minor (PM) and Triticum aestivum (TA)) growing in variable saline environment (ECe 8.0 dS m−1) was assessed and compared with the diversity of bulk soils (BS) of same environments. The significantly (P < 0.0001) highest bacterial and actinomycetes population were found in the rhizosphere of BJ whereas SA possessed higher fungal population. Phosphorus and zinc solubilizing bacteria was also found highest in BJ and TA rhizosphere, respectively. High saline soils had greater endospore forming bacterial population. The TA (0.88) and LN (0.87) rhizospheres showed significantly greater Shannon–Weiner diversity index compared to bulk soils (0.45–0.61). Pielou’s index of evenness of different samples ranged from 0.13 to 0.43. Discriminant function analysis revealed that rhizospheres of SA, CM and TA were clearly distinct. The rhizospheric soil of PM and BJ were similar to each other but clearly distinct from others. The observed separation of different biotypes was regulated by dimorphic fungi, nitrogen fixing bacteria, Pseudomonas, and fungi. Thus, our study clearly suggests that culturable microbial populations are influenced by different biotypes and salinity levels.

Chlorophyll Fluorescence - a Tool for Quick Identification of Accase and ALS Inhibitor Herbicides Performance

ABSTRACT: Chlorophyll fluorescence measurement is a precise research technique that can be used for studying the effect of herbicides with different modes of action on photosynthetic apparatus. The aim of the present project was to study the variation of the fluorescence induction curve (Kautsky curve) and its variables affected by pinoxaden (ACCase inhibitor) and mesosulfuron-methyl + iodosulfuron herbicide (ALS inhibitor) in littleseed canarygrass (Phalaris minor Retz.) and wild oat (Avena ludoviciana Durieu). This study was carried out at the Greenhouse of Collage of Agriculture at Ferdowsi University of Mashhad, during 2013. Experiments were performed based on a completely randomized design in form of a dose-response test with six doses of each herbicide plus an untreated control. The maximum quantum efficiency of photosystem II (PSII) was measured 1, 2, 3, 5 and 7 days after spraying (DAS). The results obtained in the study indicated that the estimated EDs parameters differed based on herbicide types or weed species. For example, ED90 varied from 11.67 to 28.61 g active ingredient (a.i.) ha-1. Moreover, the results showed that application of mesosulfuron-methyl + iodosulfuron at doses higher than 9 g a.i. ha-1 changed the shape of the chlorophyll fluorescence induction curve (Kautsky curve) in littleseed canarygrass at 7 DAS while herbicide doses of mesosulfuron-methyl + iodosulfuron did not change the shape of the Kautsky curve in wild oat. In addition, the Kautsky curve was observed to have an approximate permanent drop for littleseed canarygrass species at 2 DAS by pinoxaden. Comparing the fluorescence parameters in wild oat and littleseed canarygrass treated with two herbicides showed that Fv/Fm, the maximum quantum efficiency of PSII and Fvj, variable fluorescence at the J step of littleseed canarygrass decreased more than the mentioned parameters in wild oat. Furthermore, there was a strong relationship ranging from 0.53 to 0.79 between dry weights after 4 weeks and fluorescence parameters at 7 DAS depending on the herbicide type and weed species. Applying fluorescence parameters a few days after treatment to predict biomass production can be a defining criterion in research and development stages of herbicides to eliminate the need for whole plant bioassay. This method can also be applied to shorten the bioassay screening period and function as a suitable and cost effective indicator for monitoring of ACCase and ALS inhibitors. This approach also demonstrates serious damages to plant photosynthesis apparatus on crop during herbicide misapplication.

Pre-and post-emergence herbicide sequences for management of multiple herbicide-resistant littleseed canary grass in wheat

Littleseed canary grass (Phalaris minor) is the ubiquitous and pernicious grass weed of wheat in rice-wheat cropping system in north-western Indo- Gangetic plains of India. A field experiment was conducted during Rabi 2014–15 and 201516 in a farmers field infested with P. minor having history of poor control with acetyl-CoA-carboxylase inhibitors in village Nangla, district Fatehabad, Haryana, India with an objective to compare pre-emergence only, postemergence only and pre-emergence followed by post-emergence herbicide treatments for control of P. minor in wheat. The sequential application of preemergence pendimethalin 1.5 kg/ha fb post-emergence pinoxaden + metsulfuron 64 g/ha and pre-emergence pendimethalin 1.5 kg/ha fb post-emergence mesosulfuron + iodosulfuron 14.4 g/ha provided 88–93% control of P. minor compared to alone pre- and post-emergence herbicide treatments. Grain yield of wheat increased significantly by 69–78% with pre-emergence pendimethalin 1.5 kg/ha fb post-emergence pinoxaden + metsulfuron 64 g/ha or pre-emergence pendimethalin 1.5 kg/ha fb post-emergence mesosulfuron + iodosulfuron 14.4 g/ha due to significant increase in yield attributes. Alone pre- or post-emergence herbicides provided ineffective control of P. minor (44–66%) and recorded lower grain yield. It was concluded that herbicide sequences having both pre- and postemergence herbicides would be better option as compared to their alone applications in order to manage resistant populations of P minor in wheat.

Crop Growth and Yield Losses in Wheat Due to Little Seed Canary Grass Infestation Differ with Weed Densities and Changes in Environment

ABSTRACT: Understanding the weed interference with different sowing times of crop is inevitable for forecasting yield losses by weed infestation and designing sustainable weed management systems. A field experiment was carried out to evaluate the effects of sowing dates (20th November, 10th December) and various little seed canary grass (LCG) infestation levels (10, 20, 30 and 40 plant m-2) on growth and yield of wheat under semiarid conditions. Plots with two natural infestations of weeds including LCG (Unweeded control; UWC) and excluding LCG (UWC-LCG) were maintained for comparing its interference in pure stands with designated densities. A season-long weed-free (WFC) treatment was also run. All the weeds/LCG infestation levels starting from 10 LCG plants m-2 considerably reduced the wheat growth (leaf area index, crop growth rate, total dry matter accumulation) and hampered the yield contributing factors in both sowing dates. Presence of LCG was more detrimental for growth of late-sown wheat (10th Dec), therefore, 40 LCG plants m-2 recorded more reductions in growth indices of wheat even than UWC. In late sown wheat crop, the grain yield losses by 40 LCG plants m-2 and UWC were comparable, however, these losses were much greater than UWC LCG. In crux, delay in sowing of wheat not only reduced the crop growth and yield but also enhanced the LCG/weed interference. Furthermore, greater competitive ability of LCG particularly for late-sown wheat suggests that it should be controlled in order to provide healthy environment for crop plants.

Evaluation and management of acetyl-CoA carboxylase inhibitor resistant littleseed canarygrass (Phalaris minor) in Pakistan

ABSTRACTA field survey was conducted for the sampling of Acetyl-CoA carboxylase (ACCase) inhibitor resistance littleseed canarygrass, a major weed of wheat, from Punjab, Pakistan in 2014 for confirmation of resistance. The surveyed regions encompassed four different cropping systems including rice–wheat, maize–wheat, cotton–wheat and mixed cropping. Dose–response assay was conducted for confirmation of resistance. Efficacy of herbicide mixtures including clodinafop–propargyl, metribuzin, pinoxaden and sulfosulfuron at a range of doses was investigated to manage littleseed canarygrass. Results revealed that all populations were resistant to fenoxaprop except PM-BWL-2. The higher level resistance (6.5) was found in populations collected from rice–wheat cropping system. The tested herbicide mixtures at 75% and 100% of the recommended dose of each mixture component provided the effective control of resistant littleseed canarygrass. Mixtures at 50% provided more than 80% control and reduced growth and seed production potential of surviving plants. The confirmation of ACCase inhibitor resistance as the first case of herbicide resistance in Pakistan, leads us to discourage use of ACCase inhibitor herbicides alone. However, herbicide mixtures at 75% and 100% of the recommended dose are suggested to manage this weed for sustainable wheat production in the surveyed cropping systems.

Post-emergence herbicides for the control of resistant littleseed canarygrass in wheat

Farmers ’participatory field trials were conducted at village Kheri Raiwali in Kaithal district of Haryana during winter seasons of 2011–12 and 2012–13 to evaluate the bio-efficacy of post-emergence herbicides, their mixtures and sequential application for the control of the resistant littleseed canarygrass (Phalaris minor) and other weeds in wheat. Application of clodinafop 60 g/ha, fenoxaprop 120 g/ha and sulfosulfuron 25 g/ha at 35 days after sowing (DAS) did not provide satisfactory control of P. minor; however, mesosulfuron + iodosulfuron 14.4 g/ha provided better control (85–90%). Pinoxaden 50 g/ha resulted in 80% control of P. minor during first year but it provided only 55% control during second year. Ready-mix combination of metribuzin with fenoxaprop and clodinafop significantly improved the control of P. minor and broad-leaf weeds as compared to alone application of fenoxaprop and clodinafop. Maximum weed control efficiency (WCE) and highest grain yield (5.2 t/ha) was recorded with the application of sulfosulfuron + metsulfuron 32 g/ha during 2011–12, which was statistically at par with mesosulfuron + iodosulfuron and clodinafop + metribuzin; whereas during the second year, sulfosulfuron + metsulfuron 40 g/ha resulted in highest grain yield. Sequential application of sulfosulfuron + metsulfuron 32 g/ha at 25 DAS before irrigation fb sulfosulfuron + metsulfuron 32 g/ha at 40 DAS (after first irrigation) registered 97% WCE but its continuous adoption may lead to rapid development of resistance. The study indicates the need of new post-emergence herbicide with different mechanism of action (MOA), which can be integrated with non-chemical weed control strategies.

Weed spectrum in different wheat-based cropping systems under conservation and conventional tillage practices in Punjab, Pakistan

Excessive tillage in conventional agriculture has led to soil and environmental degradation. Conservation agriculture (CA) has evolved as an alternate and sustainable crop production system. However, weed control is a serious issue in CA; nonetheless, allelopathy offers a viable option for weed management. This study was conducted to evaluate the shift in weed spectra in different wheat-based cropping systems under different tillage practices in Punjab, Pakistan. Wheat was planted in fallow-wheat, rice-wheat, cotton-wheat, mungbean-wheat and sorghum-wheat cropping systems with zero tillage (ZT), conventional tillage (CT), deep tillage (DT) and CT with beds sowing (BS; 60/30 and 90/45). The most important weeds identified were fat hen, common goosefoot, horseweed, garden spurge, broad-leaved dock, yellow sweet clover, false daisy, salt marsh, rabbit foot grass, bermuda grass, red sprangletop, corn spurry and littleseed canarygrass. Maximum diversity of weeds (number of weed species) was recorded in cotton-wheat under ZT; whereas the sorghum-wheat system had minimum diversity of weeds under DT. Fallow-wheat and mungbean-wheat systems had more grassy and broad leaf weeds, respectively, while sorghum-wheat had less density of these weeds. Likewise, ZT had higher while DT and BS had less density of grassy and broad leaf weeds. However, CT favored some broad leaf weeds like fat hen and common goose foot; DT stimulated only common goose foot; whereas ZT supported some broad leaf and all grassy weeds. Sorghum-wheat system suppressed most of the weeds, grasses in particular, and three grassy weeds (salt marsh, bermuda grass and red sprangletop) were absent owing to its strong allelopathic potential; however, this system favored littleseed canarygrass under ZT. In conclusion, divergent wheat-based cropping systems had different weeds spectra under different tillage practices; and choice of cropping sequence may help suppressing weeds. Inclusion of allelopathic crops, like sorghum, in the wheat-based cropping system may help managing weeds under conventional and conservation tillage practices.

Effect of herbicide resistance on seed physiology of Phalaris minor (littleseed canarygrass)

Herbicide resistance is an evolutionary process that may involve changes in physiological and ecological traits related to plant fitness. This type of resistance occurs in littleseed canarygrass ( Phalaris minor ). This study was aimed to determine the effect of resistance to ACCase-inhibiting herbicides on fitness of seed accessions of littleseed canarygrass. Seed characteristics are important because they may determine the outcome of competition between susceptible (S) and resistant (R) biotypes. Experiments were performed to determine whether differences between S and R accessions in embryo size, dormancy, longevity, and germination speed might occur. Differences in plant fitness associated to herbicide resistance were found in seed physiological characteristics. The embryo size of R accessions was reduced up to 50 % (on a dry weight basis), which resulted in an increase in the number of days required to germinate and a reduction in the germination speed. Damage to membranes, which is related to longevity, was more severe in the R accessions. The observed decrease in seed vigor could affect the establishment of seedlings, which may explain the low success of R accessions under herbicide selection pressure.

Allelopathic potential of bread wheat helps in suppressing the littleseed canarygrass (Phalaris minor Retz.) at its varying densities

In this 2-year field study, we investigated the allelopathic effects of three wheat cultivars (Shafaq-06, Faisalabad-08 and Sehar-06) against different density levels (0, 100, 200 and 300 plants m−2) of littleseed canarygrass (Phalaris minor Retz.). Crop was sown on 1 and 3 December during 2010–2011 and 2011–2012 cropping seasons, respectively. The results showed that wheat cultivar Shafaq-06 produced more phenolic compounds at all density levels of littleseed canarygrass during both years, which caused more inhibition of littleseed canarygrass growth. More suppressive advantage of cultivar Shafaq-06 against littleseed canarygrass was responsible for its better morphological and yield related traits, and grain yield than cultivars Faisalabad-08 and Sehar-06. Among the tested cultivars, cultivar Sehar-06 had minimum allelopathic potential in suppressing littleseed canarygrass. In crux, Shafaq-06 possesses allelopathic potential to suppress littleseed canarygrass and may be used for breeding future wheat cultivars with high allelopathic activity for better weed suppression.

Interference and economic threshold level of little seed canary grass in wheat under different sowing times

Little seed canary grass (LCG) is a pernicious weed of wheat crop causing enormous yield losses. Information on the interference and economic threshold (ET) level of LCG is of prime significance to rationalize the use of herbicide for its effective management in wheat fields. The present study was conducted to quantify interference and ET density of LCG in mid-sown (20 November) and late-sown (10 December) wheat. Experiment was triplicated in randomized split-plot design with sowing dates as the main plots and LCG densities (10, 20, 30, and 40 plants m(-2)) as the subplots. Plots with two natural infestations of weeds including and excluding LCG were maintained for comparing its interference in pure stands with designated densities. A season-long weed-free treatment was also run. Results indicated that composite stand of weeds, including LCG, and density of 40 LCG plants m(-2) were more competitive with wheat, especially when crop was sown late in season. Maximum weed dry biomass was attained by composite stand of weeds including LCG followed by 40 LCG plants m(-2) under both sowing dates. Significant variations in wheat growth and yield were observed under the influence of different LCG densities as well as sowing dates. Presence of 40 LCG plants m(-2) reduced wheat yield by 28 and 34% in mid- and late-sown wheat crop, respectively. These losses were much greater than those for infestation of all weeds, excluding LCG. Linear regression model was effective in simulating wheat yield losses over a wide range of LCG densities, and the regression equations showed good fit to observed data. The ET levels of LCG were 6-7 and 2.2-3.3 plants m(-2) in mid- and late-sown wheat crop, respectively. Herbicide should be applied in cases when LCG density exceeds these levels under respective sowing dates.

Weed Management Strategies to Reduce Herbicide Use in Zero-Till Rice–Wheat Cropping Systems of the Indo-Gangetic Plains

In the rice–wheat (RW) systems of the Indo-Gangetic Plains of South Asia, conservation tillage practices, including zero-tillage (ZT), are being promoted to address emerging problems such as (1) shortages of labor and water, (2) declining factor productivity, (3) deterioration of soil health, and (4) climate change. Despite multiple benefits of ZT, weed control remains a major challenge to adoption, resulting in more dependence on herbicides for weed control. Alternative management strategies are needed to reduce dependence on herbicides and minimize risks associated with their overuse, including evolution of herbicide resistance. The objectives of this review are to (1) highlight and synthesize research efforts in nonchemical weed management in ZT RW systems and (2) identify future weed ecology and management research needs to facilitate successful adoption of these systems. In ZT RW systems, crop residue can play a central role in suppressing weeds through mulch effects on emergence and seed predation. In ZT rice, wheat residue mulch (5 t ha−1) reduced weed density by 22 to 76% and promoted predation of RW weeds, including littleseed canarygrass and barnyardgrass seeds. For ZT wheat, rice residue mulch (6 to 10 t ha−1) in combination with early sowing reduced emergence of littleseed canarygrass by over 80%. Other promising nonchemical approaches that can be useful in suppressing weeds in ZT RW systems include use of certified seeds, weed-competitive cultivars, stale seedbed practices, living mulches (e.g., sesbania coculture), and water and nutrient management practices that shift weed–crop competition in favor of the crop. However, more research on emergence characteristics and mulching effects of different crop residues on key weeds under ZT, cover cropping, and breeding crops for weed suppression will strengthen nonchemical weed management programs. Efforts are needed to integrate multiple tactics and to evaluate long-term effects of nonchemical weed management practices on RW cropping system sustainability.

Evaluation of Herbicide-Resistance Status on Populations of Littleseed Canarygrass (Phalaris Minor Retz.) from Southern Greece and Suggestions for their Effective Control

Evaluation of Herbicide-Resistance Status on Populations of Littleseed Canarygrass (Phalaris MinorRetz.) from Southern Greece and Suggestions for their Effective ControlIn 2010, a survey was conducted in the wheat fields of a typical cereal-producing region of Greece to establish the frequency and distribution of herbicide-resistant littleseed canarygrass (Phalaris minorRetz.). In total, 73 canarygrass accessions were collected and screened in a field experiment with several herbicides commonly used to control this weed. Most of the weed populations were classed as resistant (or developing resistance) to the acetyl-CoA varboxylase (ACCase)-inhibiting herbicide diclofop, while resistance to clodinafop was markedly lower. The results of the pot experiments showed that some of the canary populations were found to have a very high level of diclofop resistance (resistance index up to 12.4), while cross resistance with other herbicides was also common. The levels of resistance and cross resistance patterns among populations varied along with the different amounts and times of selection pressure. Such variation indicated either more than one mechanism of resistance or different resistance mutations in these weed populations. The population which had the highest diclofop resistance level, showed resistance to all aryloxyphenoxypropinate (APP) herbicides applied and non-ACCase inhibitors. Alternative ACCase-inhibiting herbicides, such as pinoxaden remain effective on the majority of the tested canarygrass populations, while the acetolactate synthase (ALS)-inhibiting herbicide mesosulfuron + iodosulfuron could also provide some solutions. Consequently, there is an opportunity to effectively control canarygrass by selecting from a wide range of herbicides. It is the integration of agronomic practices with herbicide application, which helps in effective management ofP. minorand particularly its resistant populations.

Optimizing the performance of diclofop‐methyl, cycloxydim, and clodinafop‐propargyl on littleseed canarygrass (Phalaris minor) and wild oat (Avena ludoviciana) control with adjuvants

Optimizing the herbicide dose by the addition of adjuvants is an acceptable way to reduce the risk of side‐effects from herbicides. Therefore, to detect a suitable adjuvant for diclofop‐methyl, cycloxydim, and clodinafop‐propargyl against littleseed canarygrass (Phalaris minor) and wild oat (Avena ludoviciana), six dose–response experiments were conducted. The treatments consisted of diclofop‐methyl at 0, 112, 225, 450, 675, and 900 g ai ha−1, cycloxydim at 0, 15, 30, 60, 90, and 120 g ai ha−1, and clodinafop‐propargyl at 0, 8, 16, 32, 48, and 64 g ai ha−1 with and without the adjuvants of Frigate, olive oil, and castor oil at 0.2% (v/v) in order to control both littleseed canarygrass and wild oat. Tested herbicides performance was enhanced by all adjuvants against littleseed canarygrass and wild oat. The addition of Frigate and the vegetable oils had the lowest and the highest effect on the performance of all of the herbicides on both littleseed canarygrass and wild oat, respectively, which confirms the solubilizing nature of the cuticular waxes by vegetable oils. A comparison between the two vegetable oils revealed that olive oil exerted a greater control of littleseed canarygrass than did the castor oil. In contrast, castor oil exerted a greater control of wild oat than did the olive oil, which can be related to differences in the leaf surface micromorphology of the weeds.

Seasonal Changes in Germination Responses of Seeds of the Winter Annual Weed Littleseed Canarygrass (Phalaris minor) to Light

Photocontrol of weeds requires knowledge about the response of weeds to light and its changes over time. Thus, littleseed canarygrass germination, as an important weed in winter crops, in response to the light environment was evaluated in seeds retrieved from different burial (10, 20, and 40 cm, under irrigated or nonirrigated conditions) or storage (room temperature 25 C and cold 3 C) conditions for 1 yr. Seeds buried in the soil showed a cyclical germination behavior when tested at 20 C, with high germination percentages (68%) occurring in August, October, and December and low percentages (12%) in February and April, with another late germination in June. Germination percentages were mostly higher for seeds incubated in light than in darkness and seeds were more likely to positively respond to light in June than at the other retrieval dates, with differences as great as 60% having been observed under irrigated conditions and at depths of 20 and 40 cm. The most outstanding effect of light as a germination stimulus was observed for seeds stored at room temperature where germination in light was always 20 to 35% higher than that in darkness. The viability of seeds did not change over time in seeds kept at room or cold temperature. However, the proportion of surviving seeds was reduced by 35 to 65% when buried in the soil. Littleseed canarygrass seeds tended to survive more when buried 40 cm deep and the differences between irrigated and nonirrigated conditions were only detectable at 10 cm deep, with higher seed mortalities under irrigated conditions. Information gained in this study would be useful in developing weed control programs for this species.

Herbicides for control of isoproturon-resistant Littleseed Canarygrass ( Phalaris minor) in wheat

Littleseed Canarygrass ( Phalaris minor) is a problematic grass weed of wheat in the North-western and the North-eastern Indian plains regions. The P. minor problem has further worsened in the North-western plains owing to the evolution of isoproturon resistance. Infestation of isoproturon R population caused >65% wheat grain yield reduction with the recommended rate of isoproturon (1000 g ha −1) application. The preference of herbicides for the management of weeds in wheat has made the alternative herbicides as the main component of resistance management strategies. Post-emergence clodinafop (60 g ha −1), fenoxaprop (120 g ha −1), pinoxaden+S (30 g ha −1 plus 0.5% surfactant), mesosulfuron+S (12–15 g+625 ml surfactant ha −1) and sulfosulfuron+S (25 g ha −1+0.35% surfactant) and pre-emergence fluazolate (150 g ha −1) and pendimethalin (1250 g ha −1) were very effective in controlling isoproturon R P. minor and improving wheat yields. To prolong the effectiveness of these herbicides, their rotational use at optimum dose and time with proper application technology should be integrated with other weed control tactics.