Biological Control Of Weeds Research Articles

Prioritisation of targets for weed biological control II: the South African Biological Control Target Selection system

ABSTRACT Invasive alien plants (IAPs) are considered one of the greatest threats to biodiversity in South Africa and are often associated with negative socio-economic and human health consequences. Biocontrol is seen as an effective strategy for managing IAPs however it can realistically only be considered for a subset of such plants given the limited funding resources available. Some plants are also better targets for biocontrol than others. This paper develops a prioritisation system to create an objective, transparent and easily usable method in which to target IAPs plants that are most suited to biocontrol in South Africa. The Biological Control Target Selection (BCTS) system builds on twelve previously developed prioritisation systems. The system uses three sections encompassing thirteen attributes that are combined to present the highest predicative powers to rank potential target IAPs as biocontrol targets.

Prioritisation of targets for weed biological control III: a tool to identify the next targets for biological control in South Africa and set priorities for resource allocation

ABSTRACT Biological control is an effective and sustainable method for management of invasive alien plants (IAPs), and has been implemented on 68 of the 367 plant species that are listed as legally requiring management strategies under South Africa’s National Environmental Management: Biodiversity Act (10/2004): Alien and Invasive Species Regulations. With limited resources and funding available, it can realistically only be considered for a subset of the remaining alien plants for which biocontrol has not yet been implemented. Considerable funding has been allocated towards biocontrol in South African in the past, principally through the Working for Water Programme of the Nature Resource Management Programmes (Department of Environment, Forestry and Fisheries), and this support is expected to continue with the intention of increasing the number of IAPs under this management approach in the future. To ensure appropriate targets are selected, the Biological Control Target Selection (BCTS) system was applied to the alien plants on this list that are not under biocontrol (299 species). This paper presents the resultant list of top priority species that represent good investments for biocontrol when funds are available.

Volatile chemistry, not phylogeny, predicts host range of a biological control agent of Old-World climbing fern

The safety of weed biological control depends upon the selection and utilization of the target weed by the agent while causing minimal harm to non-target species. Selection of weed species by biological control agents is determined by the presence of behavioral cues, namely host secondary plant compounds that elicit oviposition and feeding responses. Non-target species that elicit the same behavioral cues as found in the target weed may be at risk of damage by classical biological control agents. Here we determined volatile secondary plant constituents of the invasive weed Old World climbing fern, Lygodium microphyllum and five Lygodium non-target species. Nonmetric multidimensional scaling and permutational analysis of variance indicated that the volatile profiles for each Lygodium species were significantly distinct from one another. Qualitative and quantitative comparisons of 32 volatile constituents indicated that several, including 1-octen-3-ol, 3-octanone, sativene, δ-cadinene, and ethyl hexanoate, distinguish the non-target Lygodium species from the target L. microphyllum. We retrospectively compared the ovipositional responses of the established classical biocontrol agent Neomusotima conspurcatalis, previously tested and released for biological control of L. microphyllum to these species and found similarity of volatile profile to L. microphyllum was a strong predictor of oviposition (R2 = 0.86), while phylogenetic distance predicted neither volatile profile nor oviposition for the Lygodium species tested. These results suggest that distinct volatile profiles among Lygodium species facilitated the selection of the target weed L. microphyllum and the invasive congener L. japonicum while avoiding other, non-target species native to the introduced range for oviposition. These volatile profiles could serve as behavioral cues used by this biological control agent N. conspurcatalis to select a narrow host range.

Biological control of Parkinsonia aculeata: Using species distribution models to refine agent surveys and releases

Biological control of invasive weeds relies on the intentional release of host specific natural enemies from the native range of the weed to its invaded range. Development of distribution models for weed biological control agents presents several challenges; chief among these, especially early in biological control programs, is a paucity of ecological and biogeographic information on candidate agents in the native range to guide native range surveys or to optimise their release efforts in the invaded range. We took a ‘model tuning’ approach within the MaxEnt modelling framework to develop testable projections of the distributions of the two moth species Eueupithecia cisplatensis and E. vollonoides, biological control agent for the neotropical weed Parkinsonia aculeata. We tested these projections based on the known distribution of these moths in their native range and their population establishment in the invaded range. Our results identified new areas in the Americas where targeted surveys for these agents may be worthwhile, and also the potential for E. vollonoides to have a broader distribution in the invaded range as a biological control agent. Information gathered from future native range surveys and population establishment in the invaded range will serve as tests of the validity of the models generated and guide any refinements of the modelling framework. The approach we used may serve as a useful template for other systems with a similar paucity of information on the ecology and biogeography of the focal species, but where projections of potential distribution may be desirable.

Chevroned Water Hyacinth weevil Neochetina bruchi Hustache (Insecta: Coleoptera: Curculionidae)

Neochetina bruchi Hustache is commonly referred to as the chevroned water hyacinth weevil and is a weed biological control agent used to manage water hyacinth, Pontederia crassipes Mart. [formely Eichhornia crassipes (Mart.) Solms (Pellegrini et al. 2018)], in more than 30 countries (Winston et al. 2014). Imported from Argentina, the insect was first introduced into the United States in Florida in 1974 and released in Louisiana later in 1974 (Manning 1979), Texas 1980, and California 1982 to 1983 (Winston et al. 2014). Now Neochetina bruchi occurs throughout the Gulf Coast States (Winston et al. 2014). The target weed of Neochetina bruchi, water hyacinth, is an invasive aquatic plant in the United States and is included on Florida’s list of prohibited aquatic plants.
 Neochetina bruchi is among four species of insect biological control agents that have been introduced into the United States to manage water hyacinth. The other three species include a weevil, Neochetina eichhorniae; a moth, Niphograptaalbiguttalis; and a planthopper, Megamelus scutellaris, which were introduced into the United States in 1972, 1977, and 2010, respectively (Tipping et al. 2014).
 Although the larvae and pupae of Neochetina bruchi and Neochetina eichhorniae have similar appearance and behavior and can be difficult to differentiate by casual observation (Deloach and Cordo 1976), the adult stages of the two species of water hyacinth weevils can be distinguished relatively easily based on the color patterns on their elytra (hardened fore wings).

Assessing herbivorous insects as potential biological controls for the invasive species Miconia calvescens (Myrtales: Melastomataceae)

ABSTRACT Biological control methods may provide efficient and environmentally sustainable methods for curbing invasive weeds. Miconia calvescens DC (Melastomataceae) is an invasive weed of forest ecosystems on oceanic islands and one of the most invasive alien species. Therefore, the present study aimed to identify and assess the population dynamics of herbivorous insects that feed on M. calvescens in Brazil. The following species were found on M. calvescens plants at our three study locations: Apion sp. (Brentidae), Agrilus sp. (Buprestidae), Cryptorhynchus sp., Naupactus spp. (Curculionidae), Brasilaphthona sp., Cerotoma sp., Chrysodina sp., Colaspis sp., Diabrotica speciosa, and one unidentified species of the subfamily Cassidinae (Chrysomelidae). According to host specificity and impact caused to M. calvescens, the fruit-feeding Apion sp. and the stem-boring Cryptorhynchus sp. have high potential for this weed's biological control. Thus, our results provide useful information for potential biological control programmes for M. calvescens using herbivorous insects and will be helpful for companies working on natural weed control for this species.

Sunn hemp (Crotalaria juncea) weed suppression and allelopathy at different timings

ABSTRACT The utilisation of plant allelopathy is an important tool in a diversified weed management strategy. Allelochemicals are released by some plants, such as sunn hemp (Crotalaria juncea L.), to inhibit the growth of neighbouring plants. This species was tested for use as an allelopathic plant for weed control in cropping systems. The allelopathic properties of sunn hemp were tested under field conditions at different timings of 4, 8, 12 and 16 weeks after planting (WAP). The results showed that sunn hemp at 8, 12 and 16 WAP significantly decreased the total number of weeds compared with the control weedy check. The similar trend of decreasing weed number was observed in grass and broadleaf weeds, as well as sedge. The allelopathic activity of sunn hemp was further investigated in the soil planted with sunn hemp and water extracts on tested plants. Phytotoxicity of the soil, planted with sunn hemp at different timings, did not significantly decrease germination, shoot length, root length and dry weight of tested plants. However, the water extracts caused significantly decreased germination and plant growth, especially the shoot extracts exhibited the inhibitory effects more than the root extracts. Interestingly, the extracts from sunn hemp at 4 WAP had higher inhibitory effects than the extracts from other stages. These results suggest that sunn hemp growth stage is an important consideration for maximising biological weed control in cropping systems.

Biological weed control – prospects and limitations

Wycofywanie wielu substancji chemicznych, których zadaniem było ograniczanie występowania chorób, szkodników i chwastów, skłania środowisko naukowe do podjęcia intensywnych działań opartych na poszukiwaniu przyjaznych środowisku i nietoksycznych dla ludzi i zwierząt czynników biologicznych, które zapewniłyby zdrowotność i stabilne plonowanie roślinom uprawnym. W biologicznym zwalczaniu chwastów wykorzystuje się jednego lub więcej naturalnych wrogów (roztoczy, owadów, patogenów) na konkretny gatunek chwastu. Najważniejszym wyzwaniem w biologicznych metodach zwalczania chwastów jest zdefiniowana orientacja czynnika biologicznego na jeden gatunek (rzadziej rodzinę) chwastu. W dostępnej literaturze naukowej, coraz częściej spotyka się badania oceniające przydatność różnego rodzaju organizmów rodzimych lub obcych, które mogłyby być wykorzystane jako biologiczne środki zwalczające niektóre gatunki chwastów, a tym samym stanowiłyby uzupełnienie metod konwencjonalnych (głównie mechanicznych). Istotnym ograniczeniem w badaniach nad biologicznym zwalczaniem chwastów jest pracochłonność, dokładność badawcza i duża wiedza o możliwych interakcjach pomiędzy organizmami. Z tego powodu postęp w tym obszarze jest bardzo powolny i obarczony dużym ryzykiem niepowodzenia. W pracy dokonano przeglądu literatury dotyczącej możliwości zwalczania rodzimych gatunków chwastów metodami biologicznymi. The withdrawal of many chemical substances whose task was to reduce the occurrence of diseases, pests and weeds, prompts the scientific community to undertake intensive activities based on the search for biological agents that are environmentally friendly and non-toxic to humans and animals, which would ensure health and stable yield of crops. Biological weed control uses one or more natural enemies (mites, insects, pathogens) per species of weed. The most important challenge in biological methods of weed control is the defined orientation of a biological factor on one species (less often a family) of weeds. In the available scientific literature, there are more and more studies assessing the suitability of various types of native or foreign organisms that could be used as biological agents for controlling some weed species, and thus complement conventional (mainly mechanical) methods. A significant limitation in research on biological weed control is labour consumption, research accuracy and extensive knowledge of possible interactions between organisms. For this reason, progress in this area is very slow and carries a high risk of failure. The paper reviews the literature on the possibility of controlling native weeds with biological methods.

Impact of Zygogramma bicolorata on vegetative and reproductive performance of Parthenium hysterophorus in Nepal

Parthenium hysterophorus Linn. is one of the most aggressive, invasive weeds threatening natural and agricultural ecosystems in Nepal. Leaf feeding beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), is regarded as a potential candidate for biological control of Parthenium weed. Considering the fact effectiveness of Z. bicolorata against P. hysterophorus was evaluted in Nepal. Z. bicolorata caused 98.25 % defoliation of P. hysterophorus reducing 38.88 % plant height, 27.29 % plant width, 26.25 % root length, 12.33 % leaves, 40.58 % shoot biomass and 36.59 % root biomass in the period of 90 days. The flower production and soil seed bank were reduced by 50.22 % and 40.29 %, respectively. Z. bicolorata was an efficient bio-control agent with a significant negative effect on the vegetative and reproductive performance of the noxious weed P. hysterophorus.

Environmental Effects and Management Strategies of the Herbicides

India has wide range of agro-climates and soil types and highly diverse agriculture farming systems with different types of weed problems. So, herbicides are the integrated part of the general cropping systems. In general, herbicides are formulated in such a way that they degrade from the environment after completion of their intended work, but a few of them persist in the environment and cause a serious hazard to the succeeding crop and also to the surrounding environments. Hence, a proper knowledge of herbicides is important to understand the management procedure, organization and hierarchy of the herbicides. It also provides an imminent idea to herbicide resistance, which continues to be a problem in sustainable agricultural management. In this review, the herbicides used in India, negative impact of herbicides on the environment, persistency of herbicides, their dissipation methods and different management practices to avoid/minimize herbicide carry-over effects were discussed. The combine effects of bioaugmentation and biostimulation along with organic matter addition might be a promising technology to accelerate the biodegradation. Apart from these, extensive field evaluation studies with other tools like crop rotation and increment of the organic matter content is definitely a promising technique for managing the herbicide persistence. Bioherbicides, a biological control agent for weeds, and transgenic approaches can be a good alternative for chemical herbicides in future. They provide high degree of specificity of target weed and have no effect on non-target, beneficial plants or man and do not form any residues in the environment.

The effects of elevated atmospheric CO2 concentration on the biological control of invasive aquatic weeds

Abstract There has been a rapid increase in atmospheric CO2 concentration, from pre-industrial values of 280 ppm to more than 400 ppm currently, and this is expected to double by the end of the 21st century. Studies have shown that plants grown at elevated CO2 concentrations have increased growth rates and invest more in carbon-based defences. This has important implications for the management of invasive alien plants, especially using biological control which is mostly dependent on herbivorous insects. The aim of this study was to investigate the effects of elevated atmospheric CO2 on the biological control of four invasive aquatic weeds (Azolla filiculoides, Salvinia molesta, Pistia stratiotes and Myriophyllum aquaticum). These species are currently under successful control by their respective biological control agents (Stenopelmus rufinasus, Cyrtobagous salviniae, Neohydronomus affinis, and Lysathia sp.) in South Africa. The plant species were grown in a two factorial design experiment, where atmospheric CO2 concentrations were set at ambient (400 ppm) or elevated (800 ppm), and plants were either subjected to or not subjected to herbivory by their target biological control agents. There was an overall increase in biomass production and C:N across all species at elevated CO2, both in the absence and presence of biological control, although C:N of M. aquaticum and biomass of A. filiculoides with herbivory were not constant with this trend. Insect feeding damage was reduced by elevated CO2, except for S. molesta. Thus, we can expect that plants will respond differently to CO2 increase, but the general trend suggests that these species will become more challenging to manage through biological control in future.

Studies on the fruit feeding weevil, Paramecops farinosa (Coleoptera: Curculionidae) in Sri Lanka as a prospective weed biological control agent of invasive weed, Calotropis spp.

Calotropis gigantea is a large shrub or a small tree native to Sri Lanka with an Ayurvedic medicinal value. The plant is considered as an invasive weed in countries where it has been introduced. Paramecops farinosa Schoenherr (Aak weevil) is a monophagous pest that feeds on C. gigantea . Present study was conducted to elucidate the life history and damage potential of P. farinosa , in order to assess its potential as a biological control agent against C. procera and C. gigantea in countries where the plants are invasive. The field sampling was done throughout Sri Lanka covering 120 sampling sites from December 2014 to October 2015, and C. gigantea fruits were examined for the incidence and intensity of damage by P. farinosa . It lays yellowish, oval and mostly one-clustered eggs in the inner-pericarp fibrous layer of the Calotropis fruit. Newly emerged larvae were apodous, pale yellowish-white with brown head capsule whereas developing larvae were creamy-white, curved and stout. Paramecops farinosa larvae voraciously feed on all Calotropis seeds (100%) and fifth larval instar pupated by forming silky cocoons within the seed chamber. The adults feed on leaves, buds and flowers and its damage is highly correlated with the amount of P. farinosa inhabit on trees. P. farinosa is a seed predator and highly damage reproductive structures of C. gigantea thus directly influences the reproductive ability of the plant. These results provide baseline information needed in adopting P. farinosa as potential biological control agent against C. procera and C. gigantea .  Â

Herbicidal Characteristics and Structural Identification of the Potential Active Compounds from Streptomyces sp. KRA17-580.

Weeds are notorious plant species exhibiting a harmful impact on crops. Biological weed control is an efficient and environmentally friendly technique, usually constitutes naturally derived compounds, including bioherbicidal metabolites produced by Streptomyces sp. The isolation and structural identification of phytotoxic compounds from Streptomyces have recently been proposed as an effective way to the discovery of novel bioherbicides. In the screening of bioherbicidal agents, isolated Streptomyces strain KRA17-580 demonstrated significant phytotoxic activity against Digitaria ciliaris. Phylogenetic analysis of the 16S rRNA sequence indicated that isolated KRA17-580 is similar to Streptomyces olivochromogenes. The bacterial culture conditions were optimized for temperature, agitation, and initial pH. Streptomyces strain KRA17-580 showed intense phytotoxic activity and high cell mass at an initial pH of 5.5-7.0, more than 150 rpm, and 25-30 °C. The herbicidal compounds isolated from the culture filtrate of strain KRA17-580 were purified by solvent partition, C18, Sephadex LH20 column chromatography, and high-performance liquid chromatography. By 1D-NMR, 2D-NMR, and electrospray ionization mass spectrometry analysis, the 580-H1 and 580-H2 compounds were identified as a cinnoline-4-carboxamide (MW, 173.0490; C9H7N3O2) and cinnoline-4-carboxylic acid (MW, 174.0503; C9H6N2O2), respectively. Only these two herbicidal compounds showed strong phytotoxic activity against D. ciliaris in foliar applications. However, compound 580-H2 was more phytotoxic than 580-H1 and the toxicity was dose-dependent. The herbicidal metabolite KRA17-580 produced by Streptomyces sp. is a new bioherbicidal candidate that may provide a new lead molecule for more efficient phytotoxic compounds.

Suppression of seed production as a long-term strategy in weed biological control: The combined impact of two biocontrol agents on Acacia mearnsii in South Africa

The effectiveness of seed-reducing biocontrol agents, particularly for perennial trees with long-lived seed banks, remains a subject of debate. General consensus is that exceptionally high and consistent levels of damage are required to have any meaningful impact. In South Africa two seed-reducing agents are deployed against Acacia mearnsii, a woody mimosoid whose invasive success is attributed to high fecundity and the accumulation of persistent soil-stored seed banks. This study demonstrates that seed production has declined to extremely low levels, primarily due to a flower-galling midge, Dasineura rubiformis (Cecidomyiidae), with a seed-feeding weevil, Melanterius maculatus (Curculionidae), playing a supplementary role. No short to medium term impacts on the current density, extent or abundance of the weed are anticipated because there are sizeable seed banks in the soil which will continue to replenish any aboveground losses for many years to come. However, the dramatic reductions in annual levels of seed-fall that have been realised are anticipated to curb rates of accumulation of seed banks and curtail spread of the weed.

Large carabids enhance weed seed removal in organic fields and in large-scale, but not small-scale agriculture

ContextBiological weed control by seed predators is an ecosystem service reducing weed population densities in agricultural landscapes. Drivers of seed predation are manifold and may change with spatial scales considered.ObjectivesWe aimed at identifying the functional identity of seed predators, food web interactions and feeding links between weed and wheat seeds, considering the causal relationships between local and landscape-scale patterns.MethodsWe investigated direct and indirect effects of local management intensity in winter wheat fields (organic vs. conventional farming), local crop characteristics (wheat density and height), edge effects, landscape composition (measured as land-use diversity) and configuration (edge length) on carabid beetles of different body size (large vs. small carabids), and removal of weed and wheat seeds.ResultsWe showed the importance of indirect local- and landscape-scale effects for weed seed removal via the activity density, but not assemblage composition, of large, but not small carabids, which was driven by few ubiquitous species. The activity density of large carabids increased with decreasing wheat density and increasing wheat height, which was highest in organic fields and in landscapes with low compositional and configurational heterogeneity. Further, the availability of nutrient-rich wheat seeds enhanced weed seed removal rates.ConclusionsWe found highest weed seed removal via large carabids in organic fields in large-scale agricultural landscapes. Predator body size and species identity as well as the availability of additional food items need to be taken into account for better predicting the biological weed control potential and reducing the use of plant protection products.

Allelopathic effects of Cynara cardunculus L. extracts

Weeds are recognized as the most important biotic factor affecting yields in agroecosystems. The negative effects derived from the irrational use of herbicides have led to an increasing interest to eco-friendly practices for weed control, including the manipulation of allelopathic mechanisms. The present study aims to explore the potential use of Cynara cardunculus L. leaf extracts for the biological control of weeds and pathogen microorganisms. In a first trial, the allelopathic effects of its leaf aqueous extracts were demonstrated on seed germination of six common weeds. Secondly, the set-up of the most efficient extraction method of its allelochemicals in terms of costs, yields and inhibitory activity was realized, selecting dried leaves as the best plant material and ethanol and ethyl acetate as the best solvents. Moreover, new C. cardunculus allelochemicals (cynaratriol, desacylcynaropicrin, 11,13-dihydro-desacylcynaropicrin and pinoresinol) were purified. Third, the effect of genotype, harvest time and light stress (by plant shading) was evaluated on the phytotoxicity, quantity and composition of sesquiterpene lactones in C. cardunculus leaf extracts through a new UHPLC-MS/MS analysis method. Wild and cultivated cardoon showed the highest concentrations, while spring was the best harvest time. Moreover, light stress stimulated the synthesis of these allelochemicals. In a second trial, the effects resulting from 3-years cultivation, in two different areas, with globe artichoke, cultivated and wild cardoon were studied on the quali/quantitative composition of the weed soil seed bank and on soil eubacterial communities. In both areas, C. cardunculus reduced the weed seed bank size compared to controls. Nevertheless, the presence of cultivated cardoon had a negative influence towards Bacillus subtilis and a positive one on Pseudomonas putida and Azospirillum brasilense. Lastly, cultivated cardoon leaf extracts were assessed in vitro for the control of several microorganisms of agriculture and food interest. All the extracts showed an important antimicrobial activity, especially when using ethanol as extracting solvent.

An Experiment on the Behavioural, Morphometric, and Histopathological Effects of Paraquat Dichloride on Nile Tilapia Fingerlings

Integrated rice-fish farming has several ecological benefits, which include providing biological control of pests and weeds, and increasing rice yield from the additional nutrients derived from fish faecal matter. Unfortunately, the success of this venture is uncertain due to factors such as limited water availability for irrigation and the contamination of freshwater sources by pesticides like paraquat dichloride, which can cause chronic or acute toxicity of fishes.

Biological control of weeds: A review

Weeds are one of the main constraints to agriculture and cause 10-80% crop yield loss besides reducing product quality and leading to health and environmental hazards. Traditionally, weed control in India has been largely dependent on manual weeding. However, increased labour scarcity and costs are encouraging farmers to adopt labour and cost saving options. In comparison to various weed management strategies, biological control offers an innovative approach to address this problem. Biological management of weeds includes the use of living organisms to decrease the effect of weeds to keep at or below desirable level without significantly disturbing the crop plants. It includes use of insects, pathogens, nematodes, parasitic plants and competition plants affecting the adoption of weed biological control and the challenges to promote them are being studied in this article.

Field application of allelopathic bacteria to control invasion of little seed canary grass in wheat.

Development of successful biological weed control can help to resolve various environmental challenges created by the chemical and mechanical weed control. The current study is aimed at investigating the potential of allelopathic bacteria (hereinafter as AB) for biological weed control in wheat rather than the traditional areas of plant allelopathy, phyto-pathology, and insect biocontrol agents. Eleven strains of AB were obtained that were inhibitory to little seed canary grass of which 5 also inhibited wheat in our previous studies. The remaining strains indicated the potential for biological control of this weed in wheat. Five efficient strains were selected for this purpose to conduct pot and field trials. Seeds of little seed canary grass were sown together in potted soils with wheat seeds inoculated with AB strains. A subsequent field trial was conducted at a site selected based on chronic infestations of canary grass. Seeds of the weed and inoculated wheat were co-seeded directly in field soil. For inoculation, these strains were formulated in sterilized peat and applied to seeds. In pot trials, the invasion of little seed canary grass in wheat reduced wheat grain yield up to 59.9%. Four strains suppressed the weed which resulted in recovery wheat grain yield losses from 20.1 to 66.9%. The field trial showed that the invasion of little seed canary grass reduced wheat grain yields up to 53.9%. Four strains suppressed the weed which resulted into recovery of grain wheat grain yield losses 34.3 to 64.3%. These findings were consistent with improvement of other agronomic, physiological, and chemical parameters of the crop where the four strains of AB (L9, T42, 7O0, and O010) were applied.

Field Performance of Allelopathic Bacteria for Biological Weed Control in Wheat: Innovative, Sustainable and Eco-Friendly Approach for Enhanced Crop Production

Application of allelopathic bacteria (AB) for weed suppression may be helpful to solve various environmental challenges posed by conventional weed control techniques. In our earlier studies, around 400 strains of rhizobacteria of five weeds and wheat were isolated, screened for production of phytotoxic substances, and tested for phytotoxic activity on wild oat and little seed canary grass, and possible effects on wheat under laboratory conditions. We obtained 13 strains inhibitory to wild oat (Avena fatua L.) and 11 to little seed canary grass (Phalaris minor Retz.). Five of these (13 and 11) strains also suppressed wheat (Triticum aestivum L.) while others either stimulated or remained ineffective on wheat in separate bioassays. The success of any weed biocontrol technique, however, depends on its response under field conditions. Therefore, the present study was conducted to investigate biological weed control of the five most efficient strains of AB under natural conditions in pot and field trials. Wheat was artificially invaded with wild oat in the pot trial through seeding. Wheat of the field trial was artificially invaded with wild oat and little seed canary through seeding. The selected strains belonged to pseudomonads (Pseudomonas putida, P. fluorescence, P. aeruginosa, and P. alcaligenes) and their inocula were prepared using sterilized peat. The inoculated seeds of wild oat and wheat were sown together in a pot trial. The inoculated seeds of wild oat, little seed canary grass, and wheat were sown together in the field experiment. The field was selected based on chronic infestation of these weeds. However, weed invasion was ensured by adding seeds of weeds (inoculated with the respective strains of AB, according to treatment plan). A severe invasion of wild oat was observed in the pot trial, which reduced the grain yield of infested wheat up to 60.8%. The effectiveness of applied strains controlled 22.0–76.3% loss of grain yield of infested wheat. Weed invasion in the field trial reduced the grain yield of the crop up to 56.3% and effectiveness of the applied strains controlled 29.0–60.7% loss of grain yield of infested wheat. The study of other agronomic, physiological, and chemical parameters of the crop and weeds supported these findings. Harnessing the potential of these strains exhibited in our studies may be helpful to introduce an innovative, sustainable, and eco-friendly weed control technique for production of wheat.