Weed Density Research Articles

Ayçiçeğinde Yabancı Ot Kontrolünde Kritik Periyot ve Uygulamaların Yabancı Ot Türleri ve Çeşitliliğine Etkileri

This study was carried out under field conditions in Adana, Turkey in 2018 and 2019 to determine the critical period for weed control in sunflower depending on the daily growth temperature (GDD) and weed species. A log-logistic model with four parameters was used to determine the relationship between relative crop yield and both increased weed intervention time and length of weed-free periods. In addition, dominant weeds and weed densities were determined in the experimental area. Data obtained from different periods of weed intervention were compared with data obtained from seasonal weed-free plots. During the sunflower growing season, 37.4% – 41.04% yield loss was determined in sunflower due to weed competition. For 5% acceptable yield loss in the first year, the critical period in weed control was determined as 243-1181 GDD; this is 24-86 days after the crop emergence (DAE) . It was found between 269 and 1409 GDD (16-72 DAE) in the second year. In sunflower, it was determined that the removal of weeds from the plot in the weed-free period started within 2-3 weeks from the emergence and continued for 10-12 weeks. These findings may help sunflower growers to plan and implement cost-effective and appropriate weed control programs.

Effect of pre- and post-emergence herbicides on growth and nutrient uptake of weeds in urdbean (Vigna mungo) crop under Shivalik foothills plains of Jammu

A field study was conducted during the summer seasons of 2015 and 2016 at the Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, Chatha, Jammu and Kashmir, to study the effect of pre- and post-emergence application of herbicides on nutrients uptake by weeds and blackgram or urdbean [Vigna mungo (L.) Hepper] crop. A significant reduction in weed density and weed biomass was observed with 2 hoeing. Further, among the herbicidal treatments, imazethapyr + pendimethalin @ 1,000 g/ha as pre-emergence and imazethapyr + imazamox 80 g/ha as post-emergence significantly reduced the weed density and weed biomass. The lowest nutrient depletion by weeds, highest grain and stover yields and nutrient uptake by urdbean crop were recorded with pre- emergence application of imazethapyr + pendimethalin @ 1,000 g/ha. Thus, pre-emergence application of imazethapyr + pendimethalin @ 1,000 g/ha may be used for effective weed-management for achieving the higher seed yield (786 kg/ha and 743 kg/ha) in urdbean crop, as it provided higher net returns of (`45,205/ha and 41,364/ ha) and benefit: cost ratio of (2.56 and 2.29) to resourceful farmers of sub-tropical conditions of Jammu region.

Efficacy of doses of fenoxaprop-p-ethyl 69% EC and cyhalofop-butyl 10% EC on weed growth, yield and economics in transplanted rice (Oryza sativa)

A field investigation was conducted during the rainy season of 2019 at Agricultural Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, to study the efficacy of doses of fenoxaprop-p-ethyl 69% EC and cyhalofop-butyl 10% EC in transplanted rice (Oryza sativa L.). Among different herbicidal treatments fenoxaprop-p-ethyl 86.25 g/ha recorded lower weed density of awnless barnyard grass [Echinochloa colona (L.) Link], water grass [Echinocloa crus-galli (L.) Beauv.] and other weeds, total dry weight and higher weed-control efficiency at 58 days after transplanting, followed by cyhalofop-butyl 80.0 g/ha. Phytotoxicity on crop plants caused by the application of fenoxaprop-p ethyl 86.5 g/ha included yellowing, necrosis, stunting, and epinasty at various stages; however, phytotoxicity disappeared as the crop developed. Fenoxaprop-pethyl 86.25 g/ha markedly improved growth attributes, viz. plant height, tillers/hill, dry-matter accumulation/hill, leaf-area index, chlorophyll content and yield attributes and yield, viz. panicle length, panicle weight, panicles/hill, grains/panicle, 1,000-grain weight, grain and straw yields and net returns in comparison to cyhalofop-butyl 80.0 g/ ha and lower dose of fenoxaprop-p-ethyl 69.0 g/ha.

Effect of planting density and weed management options on growth and productivity of Indian mustard

A field experiment was conducted during the winter (rabi) season of 2018–19 and 2019–20 at Kalyani, West Bengal, to study the effect of various planting density and weed-management options on growth and productivity of Indian mustard [Brassica juncea (L.) Czern & Coss.]. The field experiment was conducted in split-plot design with 3 replications, having 30 treatments combinations including 3 planting densities in main-plot, viz. 30 cm × 15 cm, 30 cm × 20 cm and 30 cm × 25 cm; and 10 weed-management options in sub-plots which include pendimethalin @ 1.0 kg a.i./ha, oxadiargyl @ 0.08 kg a.i./ha, pendimethalin @ 1.2 kg a.i./ha, oxadiargyl @ 0.10 kg a.i./ha, pendimethalin @ 1.0 kg a.i./ha + 1 hoeing at 30 days after sowing (DAS), oxadiargyl @ 0.08 kg a.i./ha + one hoeing at 30 DAS, pendimethalin @ 1.2 kg a.i./ha + 1 hoeing at 30 DAS, oxadiargyl @ 0.10 kg a.i./ha + 1 hoeing at 30 DAS, weed free and control. Significantly lower weed density and dry-weight of weight observed with 30 cm × 20 and 30 cm × 15 cm plant spacing. Application of oxadiargyl @ 0.10 kg a.i./ha + 1 hoeing at 30 DAS and pendimethalin @ 1.20 kg a.i./ha + 1 hoeing at 30 DAS, greatly reduced different species of weeds and their dry weight. With various main-plot treatments, higher seed yield (1,838 kg/ha) of mustard was observed with the 30 cm × 20 cm planting and was statistically better than the other plant spacings. These treatments resulted in higher seed yield to the tune of 8.18 and 12.84% over the 30 cm × 15 cm and 30 cm × 25 cm plant spacings. Weed-free situation, resulted in the highest seed yield (2,230 kg/ha) and showed parity with pendimethalin @ 1.2 kg a.i./ha + 1 hoeing at 30 DAS and oxadiargyl @ 0.08 kg a.i./ha + 1 hoeing at 30 DAS. These treatments registered 93.5, 89.8 and 88.8% more seed yield over the control plots respectively. Economics revealed that, 30 cm × 25 cm plant spacing gave the maximum net returns (`29,280/ha) with benefit: cost ratio of 1.70. The highest net returns (33,850/ha) were observed from the treatment of pendimethalin @ 1.2 kg a.i./ha + 1 hoeing at 30 DAS with a benefit: cost ratio of 1.74. This was closely followed by oxadiargyl @ 0.10 kg a.i./ha + 1 hoeing at 30 DAS.

Tomato and bell pepper tolerance to preemergence herbicides applied posttransplant in plasticulture production

AbstractPreemergence (PRE) herbicides are often banded over the entire top of raised beds for broadleaf and grass control in plasticulture vegetable production systems. However, broadleaf and grass weeds may emerge from the planting holes and tears in the plastic mulch. Banded application results in herbicides applied where no holes occur, and therefore, where they are not needed. Our objective is to identify herbicides that do not harm transplanted crops when directed at transplant holes after transplant (POST) with the aim to reduce off-target applications. Therefore, we evaluated tomato and pepper tolerance to PRE herbicides applied to transplant holes 2 wk after transplant and the subsequent effects on crop tolerance and weed density. Halosulfuron, S-metolachlor, metribuzin, and pendimethalin did not injure tomato transplants, reduce height, or reduce yield. Fomesafen caused some tomato injury (7%) but had no effect on other measured parameters in Trial I. All PRE herbicides injured peppers by ≥19%, although no effect on yield was observed. Overall, halosulfuron, S-metolachlor, metribuzin, and pendimethalin can be safely applied to tomato transplant holes 2 wk after transplant with no significant crop injury nor effects on final yield, but none of the evaluated herbicides are safe for use on pepper crops.

Competence of Different Selective Herbicides for Weed Control and Productivity of Wheat in Central Telangana Zone, India

Aim: To study the effectiveness of seven (07) herbicides for the control of weeds in wheat crop.
 Study Design: Randomized Block Design.
 Place and Duration of Study: A field study was executed in the rabi seasons, 2014-15 to 2016-17 at Agricultural Research Station, Basanthpur, Telangana.
 Methodology: New molecules of herbicides were tested in different combinations and compared with the traditional weed control practice through the weed parameters viz., weed density, weed dry matter, weed index and weed persistence index. The performance of wheat crop in terms of grain yield and cost economics were noted to attest the efficiency of different herbicide treatments.
 Results: Based on the results, the pre-emergence application of pendimethalin @ 3.0 l ha-1 and a hand weeding at 45 DAS is advised to obtain maximum grain yield while the post emergence application of clodinafop propargyl @ 60 g a.i. ha-1 + metsulfuron methyl @ 4 g a.i. ha-1 at 3 leaf stage of weed is recommended for higher economic benefits.
 Conclusion: Pre-emergence application of pendimethalin @ 3.0 l ha-1 followed by a hand weeding at 45 DAS can be recommended for higher wheat crop grain yield. And in case of labour shortage, one post emergence application of Clodinafop propargyl @ 60 g a.i./ha + metsulfuron methyl @ 4g a.i./ha at 3 leaf stage of weed i.e., at 25 DAS of wheat crop can be the cost-effective weed management practice in the wheat crop.

STUDIES ON THE APPLICATION OF HERBICIDES IN RASPBERRY CULTURE TECHNOLOGY

Weed control in raspberry cultivation helps to reduce the economic impact of the weed control link on the technological cycle, as well as to eliminate competition for water, nutrients and sunlight, thus allowing their growth and development in normal parameters. Cultivation, mulching and herbicide are the most practical control measures. It is necessary to know both the density of weeds and the dominant species in order to establish the strategy to reduce weeding by plowing, herbicide or integrated measures, so that weed invasion falls below the economic damage threshold (PED). The application of herbicides to reduce the degree of weeding is based on the knowledge of the weed species existing in the crop, as well as the state of coverage of the plantation. In order to establish effective measures to reduce the invasion below the economic damage threshold, it is necessary to determine the density of weeds by the method of mapping them and to establish the predominant species. The mapping action took place in the period 2020-2021 and an attempt was made to cover the entire spectrum of weeds in the plantation, then averaging by species. Following the mapping of weeds in the raspberry plantation, the presence of 22 weeds identified inside the metric frame belonging to both the dicotyledonous and monocotyledonous classes was observed, most of them coming from the first group (Capsela bursa-pastoris, Lamium amplexicaule, Cirsium arvense, Cardaria draba, Setaria glauca, Agropyron repens, Cynodon dactylon.

Macronutrient Applications and Irrigation Regimes Impact Weed Dynamics and Weed Seedbank Augmentation in Solanum melongena L. Fields

Weeds are a major yield-limiting factor bedeviling eggplant (Solanum melongena L.) production in Russia. This study aimed to determine the influence of macronutrient rates and drip irrigation regimes on weed flora composition and potential soil contamination by weed seedbanks in the eggplant field. Three field experiments were conducted during the 2019–2021 cropping calendar. Two-factorial field experiments were designed in four blocks whereby the composition of weed flora in eggplants was examined under the influence of different macronutrient rates (40 tons manure and N140P30, 40 tons manure and N320P120K210, and control without fertilization), and three thresholds of pre-irrigation soil moisture % least moisture capacity (LMC) (in particular, 70, 80 and 90% LMC). The results demonstrated that nutrient rates contributed to a significant increase in weed density of 27.1 to 37.6%, due to an increase in the number of annual weeds (annual winter weeds and annual early spring weeds), and an increase in soil moisture threshold from 70 to 90%. Nevertheless, low moisture availability between the rows as a result of drip irrigation utilization led to a decrease in weed populations by 10.8 to 15.9%. Potential contamination of the arable soil layer with weed seed was desirably decreased, ranging from 19.8 to 21.7% with the application of fertilizers, compared with the control. Furthermore, the soil weed seedbank was considerably reduced by an increase in the pre-irrigation threshold of soil moisture.

The Influence of Different Crop Mulches on Weed Infestation, Soil Properties and Productivity of Wheat under Conventional and Conservation Production Systems.

Pakistan and other South Asian countries rely on wheat for human nutrition. However, wheat yield is declining in the region due to several biotic and abiotic constraints. Weeds are among the major factors responsible for yield decrease and farmers manage them by intensive tillage practices. Several studies have investigated the impact of various tillage practices on weed management in wheat. However, weed suppression abilities of different mulch types are rarely tested. This three-year (2019-20, 2020-21 and 2021-22) study investigated the impact of different mulch types (prepared from different crops) on weed infestation, soil properties and productivity of wheat under conventional and conservation production systems at three locations (Multan, Hafizabad and Faisalabad) in Punjab, Pakistan. The mulches included in the study were cotton sticks mulch, mungbean straw mulch, sorghum straw mulch, rice straw mulch, sunflower straw mulch, plastic mulch, and no mulch (as control). The production systems opted for wheat cultivation were conventionally tilled wheat (CTW), zero-tilled wheat (ZTW) and zero-tilled wheat sown with happy seeder machine (HSW). The CTW resulted in the lowest soil bulk density and the highest soil porosity after wheat harvest, while ZTW behaved oppositely. Similarly, incorporation of crop mulches resulted in the highest soil porosity and the lowest soil bulk density, while no-mulch incorporation and plastic mulch recorded the highest bulk density and the lowest soil porosity. Regarding mulches by production systems' interaction, CTW with sorghum straw- and plastic mulches recorded the lowest weed density and biomass, while ZTW with no-mulch recorded the highest weed density and biomass at all locations. The CTW with mungbean straw- and plastic mulches resulted in the highest yield due to significant improvement in yield-related traits. However, ZTW with sorghum straw mulch and no-mulch resulted in the lowest wheat yield. Although sorghum straw mulch suppressed weed infestation, it negatively affected wheat growth. Economic analysis revealed that CTW with mungbean straw mulch resulted in the highest gross and net incomes and benefit:cost ratio (BCR), while the ZTW with rice straw- and sorghum straw mulches produced the lowest gross and net incomes and BCR at all locations. Therefore, mungbean straw mulch is a viable option to improve wheat productivity and net economic returns under different agro-climatic conditions of Punjab, Pakistan.

Fall-sown small grain cover crops for weed suppression and soil moisture management in an irrigated organic agroecosystem

Abstract Adoption of cover crops in arid agroecosystems has been slow due to concerns regarding limited water resources and possible soil moisture depletion. In irrigated organic systems, potential ecosystem services from cover crops also must be considered in light of the concerns for water conservation. A constructive balance could be achieved with fall-sown small grain cover crops; however, their impacts on irrigated organic systems are poorly understood. Our first objective was to determine the ability of fall-sown small grains [cereal rye (Secale cereale L), winter wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and oat (Avena sativa L.)] to suppress winter weeds in an irrigated, organic transition field in the southwestern USA. Small grains were planted following the legume sesbania (Sesbania exaltata (Raf.) Rydb. ex A.W. Hill) during Fall 2012 and Fall 2013. In Spring 2013 and 2014, weed densities and biomass were determined within each cover crop treatment and compared against unplanted controls. Results indicated that both barley and oat were effective in suppressing winter weeds. Our second objective was to compare weed suppression and soil moisture levels among seven barley varieties developed in the western United States. Barley varieties (‘Arivat’, ‘Hayes Beardless’, ‘P919’, ‘Robust’, ‘UC603’, ‘UC937’, ‘Washford Beardless’) were fall-sown in replicated strip plots in Fall 2016. Weed densities were measured in Spring 2017 and volumetric soil moisture near the soil surface (5.1 cm depth) was measured at time intervals beginning in December 2016 and ending in March 2017. With the exception of ‘UC937’, barley varieties caused marked reductions in weed density in comparison with the unplanted control. Soil moisture content for the unplanted control was consistently lower than soil moisture contents for barley plots. Barley variety did not influence volumetric soil moisture. During the 2017–2018 growing season, we re-examined three barley varieties considered most amenable to the cropping system requirements (‘Robust’, ‘UC603’, ‘P919’), and these varieties were again found to support few weeds (≤ 5.0 weeds m−2). We conclude that several organically certified barley varieties could fill the need for a ‘non-thirsty’ cover crop that suppresses winter weeds in irrigated organic systems in the southwestern United States.

Novel method to manage weeds in the rainfed groundnut (var. VRI 8 and TMV 14) using nano encapsulated herbicide formulations

The groundnut crop harbours heavy weed infestation due to its small stature and slow growing nature. The current weed management practices of hand weeding and use of commercial herbicides are unsuitable because of high labour cost and inadequate moisture availability to activate herbicides. In order to release the herbicide in a smart way, this experiment aimed to study the efficacy of encapsulated herbicides . Field experiments were conducted during Kharif 2021 and late Rabi 2022 under rainfed conditions in randomised block design with three replications. The treatments consisted of sulfentrazone, oxyfluorfen, diclosulam and metolachlor in both commercial and encapsulated form using two doses, hand weeding at 20 and 40 DAS, weed free plot and weedy check. Minimum weed density (28.33 and 17.30 No./m2 at 90 DAS during Kharif and late Rabi respectively) and weed dry weight (65.33 and 61.25 g/m2 at 90 DAS during Kharif and late Rabi respectively) were observed in hand weeding at 20 and 40 DAS (T19) followed by diclosulam @ 25 g ha-1 with encapsulation (T7). Maximum weed density and weed dry weight was observed in metolachlor @ 1 kg/ha with encapsulation (T8). Higher productivity was observed in hand weeding at 20 and 40 DAS (T19) (1802 kg ha-1 and 1753 kg ha-1 pod yield during Kharif and late Rabi respectively) and higher profitability was obtained in diclosulam @ 25 g ha-1 with encapsulation (T7) (1.80 and 2.01 B:C ratio during (Kharif and late Rabi respectively). Nano-encapsulated herbicides can thus significantly improve weed control in rainfed groundnut.

Dose–Response Curves of Pelargonic Acid against Summer and Winter Weeds in Central Italy

Pelargonic acid is a non-selective post-emergence contact bio-herbicide which is registered both for cropping and non-cropping uses in several countries. Dose–response curves on the efficacy of pelargonic acid against common weeds in Mediterranean areas are not available. Dose–response curves of pelargonic acid efficacy against summer and winter annual weeds were evaluated in two field experiments (winter exp. in 2019 and summer exp. in 2020) in central Italy. Pelargonic acid was applied at five doses (1.4, 2.7, 5.4, 10.9 and 21.8 kg a.i. ha−1). Data on weed density, weed dry weight, and weed ground cover were used to calculate the efficacy of pelargonic acid against winter and summer weeds. Data were subjected to a non-linear regression analysis using the logistic dose–response model. Dose of pelargonic acid required to obtain 50%, 70%, 90% and 95% weed control against each weed species (ED50, ED70, ED90 and ED95) were estimated. ED values allowed us to classify winter and summer weeds with respect to their susceptibility to pelargonic acid (ED50 values in kg ha−1 are reported in parenthesis): Kickxia spuria (2.6) (more susceptible) > Heliotropium europaeum (3.0) > Echinochloa crus-galli (3.4) > Solanum nigrum (3.6) > Stachys annua (5.3) > Papaver rhoeas (6.5) > Veronica hederifolia (10.3) > Amaranthus retroflexus (11.4) > Matricaria chamomilla (11.6) > Portulaca oleracea (18.7) > Lolium multiflorum (>21.8) (less susceptible). These findings will allow for the optimization of weed control by pelargonic acid and its use in weed management strategies, both in organic and sustainable cropping systems, under different environmental conditions.

Effect of Different Herbicides and Allelochemicals on Weed Density and Soil Microbial Population under Direct Seeded Rice (Oryza sativa L.)

The use of herbicides for weed control often catches the eye of environmentalists as it harms the soil microflora leading to deteriorated soil health. So, efforts are being made in order to use herbicides that can cause no or very less harm to the soil microflora. In this context, an experiment is planned to know the potential effect of different herbicides and allelochemicals on weed density and soil microbial population under direct seeded rice where herbicide weed management is widely adopted. The experiment is conducted during Rabi, 2020 and summer, 2021 in the red sandy loams of Gandhi Krishi Vignana Kendra (GKVK), University of Agricultural Sciences, Bengaluru by using randomized complete block design with three replications. Out of different treatments tried out, T4 i.e., bispyribac sodium 10 SC 40 g a.i. ha-1 as post emergence has reported superior weed control which is evident by the lower weed density (43.3 no. m-2) and weed dry weight (49.2 g m-2) followed by T1 i.e., bensulfuron methyl + pretilachlor 6.6 GR 660 g a.i. ha-1 as pre emergence (46.0 no. m-2 and 51.4 g m-2, respectively). When soil microbial population is considered all the allelochemical treatments has recorded higher microbial population but the weed control in these allelochemical treatments was not satisfactory. Among the herbicides, T1 i.e., bensulfuron methyl + pretilachlor 6.6 GR 660 g a.i. ha-1 as pre emergence has recorded higher microbial population of bacteria, actinomycetes and fungi (23.52 x 105, 15.30 x 104 and 12.45 x 103 CFU g-1 soil, respectively) over T4 i.e., bispyribac sodium 10 SC 40 g a.i. ha-1 as post emergence (21.83 x 105, 13.33 x 104 and 10.91 x 103 CFU g-1 soil, respectively). Hence, by taking both weed control and soil microbial population into consideration treatment T1 i.e., bensulfuron methyl + pretilachlor 6.6 GR 660 g a.i. ha-1 as pre emergence is concluded to be the better herbicide.

KEEFEKTIFAN HERBISIDA IPA-GLIFOSAT (480 g/l) DALAM MENGENDALIKAN GULMA PADA BUDIDAYA KELAPA SAWIT TBM

The objective of this study was to evaluate the herbicide effectiveness of IPA-Glyphosate (480 g/l) in control the common weeds on immature oil palm plantation. This study was performed in oil palm plantation at Rasau Jaya, Kubu Raya Regency, Kalimantan Barat Province. Vegetation analysis was conducted by using the square methods. Herbicide application carried out by a spraying method. Experiment arranged by randomized block design with 6 treatments and 4 replications. The results showed at 12 weeks after application the average density of weeds covering is 2,4-40%. The IPA- Glyphosate herbicide (480 g/l) with dose 5 l/ha effective suppressed the growth kinds of weeds up to 12 weeks after application and didn’t cause phytotoxicity in oil palm plantation.Keywords : common weeds, immature oil palm, IPA-Glyphosate 480 g/l

Conservation agriculture practices lead to diverse weed communities and higher maize grain yield in Southern Africa

Weed development is one of the major constraints to cereal cropping systems in Southern Africa with potential severe crop losses. Understanding weed community responses to different conservation agriculture (CA) components ( i.e ., no-tillage, NT; crop rotation, R; and mulching, M) and/or their combinations is crucial in Southern Africa where farmers apply different combinations depending on local context. Here, for the first time, we assessed how weed density, community diversity and structure respond to different combinations of CA components [conventional tillage (CT), CT+M, CT+R, CT+M+R, NT, NT+M, NT+R, NT+M+R]. The study was carried out over three seasons at two locations with contrasting soil textures i.e ., clayish, and sandy. At the sandy location, across seasons, weed density (number of individuals per unit area) and community diversity (distribution of individuals within the species) were significantly and positively affected by precipitation and not by cropping system. Weed richness (number of species) was affected by the interaction of season and cropping system, with the highest number of weed species being recorded in the NT+M+R system in the seasons with medium to high precipitation. At the clayish location, an opposite pattern was observed, and weed density was lower in seasons with medium-high precipitation than under low precipitation. Weed community diversity was 50 % higher under NT+M than under CT+R, whereas weed species richness decreased with the increase of precipitation. At both locations, the implementation of rotation and mulching either in NT or CT systems resulted in the modification of the structure of weed community with respect to CT and NT alone, and these CA combinations were associated with highest maize grain yield. Overall, eight weed species common to both locations were responsible for most of the community structure differences among cropping systems. Structural equation modelling showed that at the sandy location precipitation did not affect grain yield, but positively affected weed density, diversity, evenness, and richness. By contrast, at the clay location, precipitation positively affected grain yield, but did not modify weed density and evenness, and reduced weed community diversity and richness. At this location, weed density negatively affected grain yield. The differential weed-crop relationship supports the need to find a site-specific equilibrium between the control of weeds and the maintenance of their diversity. • Rotation & mulch in no-tillage-NT & conventional tillage-CT modified weed community. • In sandy soil rainfall positively affected weed density & diversity and not yield. • In sandy soil weed diversity positively affected grain yield. • In clay soil rainfall positively affected yield & reduced weed diversity & richness. • In clay soil, weed density negatively affected grain yield.

Association between Predatory Arthropods and Weeds on Sugarcane Plants

While a large number of farmers in the tropics consider weeds to be just a nuisance, some weeds can potentially have benefits for cultivated crops. Weeds around cultivated plants can act as a biocide, soil improvement, and a food source for humans and animals, as well as a habitat for some insects. Based on the regression analysist, weed density has a relationship to the diversity of predatory arthropod species (R2= 0.026; P<0.001) and the abundance of individual predatory arthropods (R2= 0.010; P<0.001). Beneficial weeds around sugarcane plantations create mutually beneficial interactions. Weeds can be used as a place to live, reproduce, and produce nutrients for predatory arthropods. Research on the role of weeds against natural enemies from predators in sugarcane agroecosystems is also rarely studied. In this study, the focus was on the association of weeds with the diversity and abundance of predatory arthropods in the sugarcane agroecosystem.

Determination of weed species, density, frequency and coverage areas in sugar beet (Beta vulgaris L.) fields located in Kahramanmaras and Adana provinces

Aims: This study was carried out to determine the weed species, density, frequency and general coverage area in sugar beet fields located at several districts in Kahramanmaras and Adana provinces. At the same time, it is aimed to determine the changes occurred in sugar factory production areas and weed species and density 20 years after 2000-2001. Methods and Results: In order to calculate the weed density seen in the study areas, 40 frames per 1 ha were used. The species, density, frequency of incidence and general coverage areas of weeds were calculated. Weed species; Sinapis arvensis L., Chenopodium album L., Echinochloa colonum (L.) Link., Cuscuta campestris Yunck., Amaranthus retroflexus L., Sorghum halepense (L.) Pers., Elymus repens (L.) Gould., Convolvulus arvensis L., Cirsium arvense (L.) Scop. and Cardaria draba (L.) Desv. were detected very intensely in sugar beet fields. The frequency of incidence and general coverage area of important weed species was calculated between 64.9-50.1 % and 62.8-50.0 %.Conclusions: A total of 88 weed species belonging to 26 families were determined in the sugar beet fields in the districts of Kahramanmaraş and Adana. From these weed species, 1 species belongs to holoparasite and pteridophyta, 18 species belong to monocotyledons and 68 species belong to dicotyledon class. According to the results of the research carried out 20 years ago in Kahramanmaras sugar beet fields, significant increases were observed both in the number of species and in the number of species that are very dense.Significance and Impact of the Study: Weed species and densities, detected in sugar beet fields in Kahramanmaraş and Adana provinces, vary according to district. Holoparasite C. campestris and some weed species with rhizome and stolon stems are a major threat to sugar beet in terms of density.

Predicting common bean (Phaseolus vulgaris) productivity according to Rhizoctonia root and stem rot and weed development at field plot scale.

A two-year research trial was conducted to evaluate progression of common bean (Phaseolus vulgaris) growth, Rhizoctonia root rot and weed development in association with productivity when treated with different cultivars, planting dates and weed control methods in north-western part of Iran. To determine the best descriptors, six standard curves were examined to model development of bean dry matter, Rhizoctonia root rot incidence, and weed density during two growing seasons across 256 field plots. Exponential and linear-by-linear models were fitted to bean-disease-weed progression data, and then model parameters representing over-season progress curve elements were used in multivariate regression analyses to estimate bean production. Furthermore, using herbicides (Imazethapyr and Trifluralin) restricted weed density by 28% in early (mid-spring) and 42% in late (late spring to early summer) plantings. Late plantings of two bean cultivars decreased disease progress up to 36% for herbicide use, hand-weeding and control. Although bean dry matter, pod and seed production for herbicide use and hand-weeding treatments were 6-17% greater than control, late planting improved productivity in control by 10-24%. Findings suggested that late planting of bean improved efficiency of herbicides to control weeds. Late planting also restricted Rhizoctonia root rot progress and thus, improved bean yield. There were significant correlations between bean-disease-weed development descriptors. According to principal component analysis, bean-disease-productivity-weed variables accounted for 80% of total data variance. Such information extends our understanding of bean-disease-weed progress in interaction with planting date to develop more effective and sustainable integrated Rhizoctonia management programs.

Protective enzyme activity regulation in cotton (Gossypium hirsutum L.) in response to Scirpus planiculmis stress.

Scirpus planiculmis, an important weed in rice and cotton fields, stresses crop growth and development, leading to yield loss. However, it is unclear how stressed plants respond to this weed. In this study, we analysed the stress effect of S. planiculmis on cotton under different weed densities, competition periods, and distribution conditions from the perspective of morphogenesis, physiological metabolism and crop yield. The effect of a low dose of herbicide on the relationship between cotton and S. planiculmis was also explored. The results showed that plant height, stem diameter, fresh weight, root length, boll number, single boll weight and yield of cotton all decreased with increasing S. planiculmis density and damage. The spatial distribution of S. planiculmis had no significant effect on plant height, stem diameter, fresh weight or root length of cotton, but crop yield loss decreased with increasing distance. S. planiculmis stress altered cotton chlorophyll, soluble protein and malondialdehyde (MDA) content, and protective enzyme activities. Compared with superoxide dismutase (SOD) and peroxidase (POD) activities, catalase (CAT) activity was increased under different S. planiculmis stress conditions. Therefore, we concluded that CAT plays a key role in protecting enzymes involved in defence responses. Under low-dose herbicide action, the activities of protective enzymes were increased, which helped cotton plants to resist S. planiculmis stress. The results revealed that regulating protective enzyme activities is important in cotton responses to S. planiculmis stress.

Screening of Herbicides in Transplanted Finger Millet [Eleusine coracana (L.) Gaertn

Background: Weeds smother the finger millet due to crop’s slow growth during the initial stages which reduces the yield substantially by 5-70%. Intensive use of herbicides is gaining popularity among the farmers now a days due to its effectiveness in controlling weeds, timeliness and reduced cost. Methods: The current field experiment was conducted at Tamil Nadu Agricultural university during kharif season, 2021 under irrigated condition with twelve herbicide treatments laid out in Randomized Complete Block Design (RCBD) with three replications. Result: Pre-emergence application of pyrazosulfuron ethyl 15 g ha-1 significantly reduced the total weed density and total weed dry weight at 90 days after transplanting over all the other herbicides used. This treatment also considerably improved the plant parameters such as plant height, total number of tillers, plant dry matter production, Grain and stover yield and yield parameters such as productive tillers, ear head weight of transplanted finger millet which was statistically followed by the application of pendimethalin 750 g ha-1 as pre-emergent spray. Similar trend was followed in case of net returns and B: C ratio. while lower plant parameters were observed with the application of tembotrione 12 g ha-1.