Role Of Weeds Research Articles

Enhancing Rice Yield in Paddy Fields Through Beneficial Organisms

In recent years, the global food-insecure population has increase. To improve food production while safeguarding the environment, ecological intensification techniques have become crucial. Considering rice's significance in feeding half the world, here we focused on the role of weeds, birds, and dragonflies, organisms that naturally occur in crop fields, in a paddy field in Brazil. We observed no significant differences in rice production between areas with or without a second weeding. However, access restriction experiments revealed that the presence of birds and dragonflies led to a remarkable 37% increase in rice yield, equivalent to approximately 71.6 additional bags per hectare. Results reinforce that promoting biodiversity-friendly practices in agriculture is essential for sustainable farming and aligns with global biodiversity initiatives, including COP 15, the 43rd Conference of FAO, and the Sustainable Rice Platform's Standard for Sustainable Rice Cultivation. Emphasizing these practices will not only enhance food production but also contribute to a healthier environment for generations to come.

The role of weeds as a source of beneficial microorganisms

The role of weeds as a source of beneficial microorganisms

In-depth study of tomato and weed viromes reveals undiscovered plant virus diversity in an agroecosystem

BackgroundIn agroecosystems, viruses are well known to influence crop health and some cause phytosanitary and economic problems, but their diversity in non-crop plants and role outside the disease perspective is less known. Extensive virome explorations that include both crop and diverse weed plants are therefore needed to better understand roles of viruses in agroecosystems. Such unbiased exploration is available through viromics, which could generate biological and ecological insights from immense high-throughput sequencing (HTS) data.ResultsHere, we implemented HTS-based viromics to explore viral diversity in tomatoes and weeds in farming areas at a nation-wide scale. We detected 125 viruses, including 79 novel species, wherein 65 were found exclusively in weeds. This spanned 21 higher-level plant virus taxa dominated by Potyviridae, Rhabdoviridae, and Tombusviridae, and four non-plant virus families. We detected viruses of non-plant hosts and viroid-like sequences and demonstrated infectivity of a novel tobamovirus in plants of Solanaceae family. Diversities of predominant tomato viruses were variable, in some cases, comparable to that of global isolates of the same species. We phylogenetically classified novel viruses and showed links between a subgroup of phylogenetically related rhabdoviruses to their taxonomically related host plants. Ten classified viruses detected in tomatoes were also detected in weeds, which might indicate possible role of weeds as their reservoirs and that these viruses could be exchanged between the two compartments.ConclusionsWe showed that even in relatively well studied agroecosystems, such as tomato farms, a large part of very diverse plant viromes can still be unknown and is mostly present in understudied non-crop plants. The overlapping presence of viruses in tomatoes and weeds implicate possible presence of virus reservoir and possible exchange between the weed and crop compartments, which may influence weed management decisions. The observed variability and widespread presence of predominant tomato viruses and the infectivity of a novel tobamovirus in solanaceous plants, provided foundation for further investigation of virus disease dynamics and their effect on tomato health. The extensive insights we generated from such in-depth agroecosystem virome exploration will be valuable in anticipating possible emergences of plant virus diseases and would serve as baseline for further post-discovery characterization studies.5s1csuTeBEFLkorHCziRqaVideo

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.

THE FORMATION OF THE BOTANICAL COMPOSITION OF WINTER RYE CROPS DEPENDS ON THE INFLUENCE OF DIFFERENT PREDECESSORS

The article highlights the influence of different predecessors on the cultivation of winter rye. The expediency of cultivation is proved and the importance and features of this crop as a food and fodder crop are indicated. The role of weeds and their impact on winter rye crops is also outlined. Winter rye belongs to high-yielding cereals. Advanced farms harvest 40-50 c/ha and more of grain. The experience of these farms is highlighted in the analysis of scientific literature sources, which indicates the presence of reserves for increasing the yield of rye in Ukraine. It is grown mainly for grain, as well as for green fodder (often in mixtures with winter vetch, winter rape). Rye bread has high nutritional and taste qualities due to its high content of proteins, vitamins (A, B, E) and high energy value. Rye grain is of great importance as a concentrated feed for farm animals. Rye flour is used for feeding pigs, and bran - for cattle. In a mixture with winter vetch and winter rape, rye in spring gives the earliest green fodder for animals. It is noted that weeds are most often present in crops of field crops from the groups of rhizome perennial weeds and root-sprouting weeds. Quite often there are pink thistle (Crisium arvense L.), field bindweed (Convolulus arvensis L.), creeping wheatgrass (Elytriga repens L.), horsetail (Equisetum arvense L.), creeping bitterweed (Acroptilon repens L.) and others. Among the most aggressive species are representatives of winter and biennial dicotyledonous wintering weeds. The most commonly found in winter rye crops are the following representatives: wild poppy (Papaver rhoeas L.), wild violet (Viola arvensis.), odorless chamomile (Matricaria perforate), wild poppy (Papaver rhoeas L.), common bindweed (Capsella bursa-pastoris), Sophia's curlyleaf (Descurainia sophia L. ), clinging feverfew (Galium aparine.), field axes (Consolida regalis S.), Sophia's curlyleaf (Descurainia sophia L.), medium starwort (Stellaria media), white pupal (Melandrium album), Sophia's descurainia (Descurainia Sophia), field thalassa (Thlaspi arvense). It was found that the correct selection of the predecessor for the cereal crop of winter rye will be able to satisfy high grain productivity, which will allow maintaining the agrophytocenosis in proper condition in relation to the negative impact of weed infestation and will help to reduce the overall number and species composition of segetal vegetation in winter rye crops.

Effects of Various Agroecosystem Landscape on Arthropod Diversity: A Study Case in Kemiri Village, Jember, Indonesia

Agroecosystem landscapes have been studied extensively and it is known that there is a relationship between the spatial structure and the ecological processes. The composition of arthropods in the agroecosystem shows population differences that are closely related to the location. This study aims to isolate and analyze the interactions of arthropods and landscape structures and features of different agroecosystems landscapes in Kemiri, Jember, Indonesia. The plot method (20x20 m and 1x1 m dimension) was carried out to observe seedling, sapling, and tree (seedling h = 0-1.5 m, sapling h ≥ 1.5 m, tree D > 20 cm). The trees' species name, distance, number, and DBH were collected. Arthropods were sampled using PFT and SN methods. A vial (d=5 cm) was used for PFT, and SN was applied at a distance of 1x10 meters with 3 repetitions. Plants with the role of weeds in monoculture dominate (TA=45). Drosophilidae is the most recorded family in monoculture. Polyculture and agroforestry systems increased the diversity of arthropods in the vegetation, and Formicidae predominated by PFT (TA=28% and 81%, respectively). PCA shows the role of detrivores is mostly found in agroforestry, and herbivores dominate the monoculture. CCA shows that detrivore association in agroforestry is influenced by humidity, and herbivores are particularly interested in monoculture systems that provide high light, temperature, and wind intensity. Keywords: Agroforestry, Arthropods, Effects, Monoculture, Polyculture

Biochemical Diversity, Pathogenicity and Phylogenetic Analysis of Pseudomonas viridiflava from Bean and Weeds in Northern Spain.

Pseudomonas viridiflava was originally reported as a bean pathogen, and subsequently as a wide-host range pathogen affecting numerous plants species. In addition, several authors have reported the epiphytic presence of this bacterium in “non-host plants”, which may act as reservoir of P. viridiflava and source of inoculum for crops. A new biotype of this bacterium, showing an atypical LOPAT profile, was found in Asturias, a Northern region of Spain, causing significant damage in beans, kiwifruit, lettuce, and Hebe. In order to investigate the involvement of weeds in bean disease, samples were collected from beans and weeds growing in the same fields. A total of 48 isolates of P. viridiflava were obtained, 39 from weeds and 9 from beans. 48% and 52% of them showed typical (L− O− P+ A− T+) and atypical (L+ O− P v A− T+) LOPAT profiles, and they displayed high biochemical diversity. Regarding virulence factors, the T-PAI and S-PAI pathogenicity islands were found in 29% and 70.8% of the isolates, 81.2% displayed pectinolytic activity on potato slices, and 59% of the weed isolates produced symptoms after inoculation on bean pods. A phylogenetic tree based on concatenated rpoD, gyrB, and gltA sequences separated the strains carrying S-PAI and T-PAI into different clusters, both containing isolates from beans and weeds, and pathogenic as well as non-pathogenic strains. Closely related strains were found in the two hosts, and more than half of the weed isolates proved to be pathogenic in beans. This is consistent with the role of weeds as a reservoir and source of inoculum for bean infection. Detection of P. viridiflava in weeds throughout the year further supports these roles.

Weedy Hosts of the Diaprepes Root Weevil in Florida Sugarcane

This publication provides an overview of Diaprepes root weevil and the role of weeds in providing harborage for the insect. Written by D. Calvin Odero and Ron Cherry, and published by the UF/IFAS Agronomy Department, July 2021.

Do Weeds Hinder the Establishment of Native Plants on a Reclaimed North American Boreal Mine Site?

The majority of plant diversity in the boreal forest of northern Alberta, Canada is comprised of native understory plant species that are continuously facing competition from other species, including both undesirable native and weedy species. In oil sands mine reclamation, cover soils rich in organic matter are used to cap overburden materials. The aim of this study is to understand the role of weeds on different reclamation cover soils (forest floor-mineral mix and peat-mineral mix) and determine if they hinder the establishment of the native plant community. This study was conducted four growing seasons after site establishment in June 2019. At that time, both soil types had approximately 45% total cover, had 21 species per plot, and were composed of mainly native vegetation. Competition from non-native forbs (11% average cover, mainly Sonchus arvensis and Melilotus alba) did not seem to impact the development of the native vegetation community on either soil type given the high cover and richness of native forbs. However, native graminoids (predominantly Calamagrostis canadensis) were associated with reduced native forb cover and richness at graminoid cover greater than 17%. Overall, non-native forbs appeared to have little impact on the native forb community on either soil type while native graminoids had a negative influence. We suggest that the classification of what is considered an undesirable weedy species should be evaluated in the context of ecosystem management goals rather than simply the presence of non-native species.

Phenotypic and genotypic analysis of Pseudomonas syringae recovered from symptomatic beans and associated weeds in Northern Spain

Thirty isolates of Pseudomonas syringae other than pathovar (pv.) phaseolicola, recovered from beans (18) and weeds (12) in a Northern Spanish region, were studied by a polyphasic approach, including phenotypic tests, detection of levansucrase and toxin (syringomycin and syringopeptin) genes, typing by RAPD (Random Amplified Polymorphic DNA) and PFGE (Pulsed-Field Gel Electrophoresis). The isolates were phenotypically heterogeneous, and both RAPD and PFGE, probed to be highly discriminative, as they were almost able to differentiate at the level of isolate. Phylogenetic analysis based on conserved genes of the core genome (rpoD, gltA and gyrB) distributed the isolates in three different clades (2A, 2B and 2C) belonging to phylogroup 2 of the P. syringae complex. According to toxin production, 18 of them, within clade 2B, were assigned to P. syringae pv. syringae and five of these caused symptoms after experimental inoculation on bean pods. Four of the five pathogenic isolates were obtained from weeds, supporting the role of weeds associated with bean crops, particularly Cyperus rotundus, Malva sylvestris, and Polygonum lapathifolium, as a reservoir of the pathogen. In conclusion, results of this study suggest that apart from P. syringae pv. phaseolicola, P. syringae isolates circulating in our region are mostly epiphytes, and support the role of weeds associated with bean crops as reservoir of pathogenic strains of P. syringae pv. syringae.

Modelling weed management strategies to control erosion in rubber plantations

The role of weeds in soil conservation in agroforestry systems has been largely ignored. We used the Land Use Change Impact Assessment (LUCIA) model to simulate the effects of weed management on erosion in rubber plantations (Hevea brasiliensis Muell. Arg). In order to quantify the impact of a dynamic, spatially explicit multi-layer plantation structure on erosion processes in agroforestry systems, we updated LUCIA's erosion module. Its new version simulates soil detachment due to rainfall and runoff, considering the separate effects of the tree canopy and surface cover on soil erosion. The updated LUCIA model was calibrated and validated based on an established rubber plantation experiment in Xishuangbanna, Southwest China, to evaluate the impact of different weeding strategies on soil loss. The model successfully represented the impact of the dynamic multi-layer structure on erosion and was able to predict well the effects of weed management on soil loss and runoff at the test site over 1 year, with a modelling efficiency (EF) of 0.5–0.96 and R2 of 0.64–0.92. Subsequently, we validated the ability of the model to simulate surface cover changes under rubber plantations of different age (up to 40 years). Simulation outputs for 4-, 12- and 18-year-old rubber plantations revealed satisfying to good results. However, the predicted change in surface cover for old rubber plantations (25- and 36-year) failed to meet the field trends. The model predicted the greatest erosion in the year when the rubber canopy started to close. During this period, weed growth was limited by light, while litter input from rubber was insufficient to provide good soil cover. Four weeding strategies (“clean-weeding”, “twice-weeding”, “once-weeding” and “no-weeding”) were designed for scenario simulations. Based on the results of 20-year runs, we concluded that “once-weeding” and “no-weeding” both efficiently minimized soil loss during one rotation length. A high degree of surface and weed cover (over 95% and 60%) under “no-weeding” makes this management strategy with dense undergrowth hardly acceptable by local farmers due to reduced tree accessibility for tapping and increased potential danger through poisonous caterpillars. “Once-weeding”, on the other hand, controlled overgrowth of understory vegetation by keeping weed cover below 50%. We therefore suggest “once-weeding” as an improved herbicide management strategy in rubber plantations, to meet ecological system service maintenance and to facilitate adoption in practice.

Evaluation of Weeds as Virus Reservoirs in Watermelon Crops

ABSTRACT: Watermelon is one of the most important vegetable crops in Brazil, which is grouped among the greatest producers worldwide. Viruses stand out among the most damaging disease agents, which can drastically reduce fruit production. In this context, weeds present in the field can also interfere in crop production, acting as reservoirs for viruses. Thus, this study aimed to investigate virus occurrence in weeds at the main watermelon-growing regions in the State of Tocantins. Viruses identification (e.g. potyviruses: Watermelon mosaic virus - WMV; Papaya ring spot virus - type watermelon -PRSV-W; Zucchini yellow mosaic virus- ZYMV; the cucumovirus Cucumber mosaic virus - CMV, and the orthotospovirus Zucchini lethal chlorosis virus - ZLCV) infecting weeds was performed by serology and confirmed by RT-PCR tests. Serological and molecular test results indicate that Amaranthus spinosus, Nicandra physaloides, Physalis angulata and Heliotropium indicum were infected by at least one virus species. The highest infection rate was represented by ZYMV (52.7%), followed by PRSV-W (22.2%); CMV, WMV, and ZLCV that showed the same infection rate (8.3%) each. Plants of P. angulata were infected by all five viruses, singly or in mixed infection, and represented 50% of the total number of infected samples. The highest virus infection rates, 50% and 44.4%, occurred in weeds collected at Lagoa da Confusão and Formoso do Araguaia, respectively. The results on occurrence and distribution of viruses infecting weeds in watermelon commercial plantations in the State of Tocantins provide important information about the role of weeds as virus reservoirs contribute to the knowledge of the epidemiology of these diseases, and enable a proper weed management aiming at reducing the secondary spreading control of viruses by insect vectors.

Pest categorisation of Xanthomonas oryzae pathovars oryzae and oryzicola.

The EFSA Panel on Plant Health performed a pest categorisation for Xanthomonas oryzae pathovars oryzae (Xoo) and oryzicola (Xoc), the causal agents of the bacterial blight and the bacterial leaf streak of rice, respectively. These pathovars are widely distributed in Asia, Africa and Australia. Xoo is also reported in some states of the USA and in some other countries of America. The identity of both pathovars is well established and efficient identification methods are available. The major host is cultivated rice (Oryza sativa), but different Oryza spp. as well as Poaceae weeds are reported as alternative hosts, with some uncertainty concerning the actual host range. Both pathovars are seed associated, despite the fact that seed transmission is still controversial for Xoo. Both pathovars are already regulated in Directives 2000/29/EC, on harmful organisms for plants, and 66/402/EEC, on the marketing of cereal seeds. The main pathway for entry is seed. Should these pathovars enter into EU, they may establish and spread, and they may have an impact on the rice crops, with uncertainties. The knowledge gaps identified are (1) the quantity of EU importation of rice seeds, (2) the risk of introduction through unprocessed rice for consumption, (3) the suitability of the EU growing climate conditions for the bacteria to establish and spread, (4) role of seed transmission (Xoo), (5) the role of weeds in the epidemiology and especially in seed transmission and dispersal, (6) host range of weeds. As none of the pathovars is known to occur in the EU, they do not meet one of the criteria for being considered as Union regulated non‐quarantine pests. Nevertheless, both pathovars meet the criteria assessed by EFSA for consideration as Union quarantine pest.

The role of weeds in the epidemiology of pospiviroids

SummaryMany weeds that are closely associated with horticultural activities are known as natural reservoirs of plant viruses. However, whether these weeds can also serve as hosts of pospiviroids is not well known. Pospiviroids are naked, non‐coding RNA pathogens that cause severe economic damage in many solanaceous crops. In this study, we examined the overall risk of pospiviroid spreading from weeds to economically important crops, by combining the results from previous inoculation studies with new results coming from a survey, a contact experiment and an inoculation experiment. A survey of commercial ornamental glasshouses revealed that ornamental plants mainly belonging to the Solanaceae harbour pospiviroids, in contrast to weed species sampled in the same places. No new weed hosts could be identified after testing weeds that grew in contact with Tomato apical stunt viroid (TASVd)‐infected plants of tomato (Solanum lycopersicum) and jasmine nightshade (Solanum jasminoides) in an experimental glasshouse. Finally, in mechanical inoculation experiments with TASVd, none of the six tested weed species were determined to be a host at 6 weeks after inoculation. Commonly occurring weed species therefore do not appear to play a significant role as reservoir hosts for pospiviroids. This does not rule out other potential weed hosts that have not yet been tested. Inoculation studies should include rigorous experimental protocols with a sufficient number of replicated as well as adequate positive controls. The information gained through this study may prove useful in future risk assessments for the pospiviroid group.

Preceding crop and weed management history affect denitrification and denitrifier community structure throughout the development of durum wheat

Aside from negative impacts on crop yield, the role of weeds in agricultural systems, particularly with respect to below ground function, is not well understood. In this study, we utilised a mesocosm approach with soils collected from a long-term rotation study to compare legacy effects of previous flax (Linum usitatissimum L.) or canola (Brassica napus L.) and different levels of weediness established over a decade by different herbicide use patterns. Despite few significant differences in initial soil chemical properties, the impact of level of weediness superseded that of the preceding crop and altered the growth of durum wheat (Triticum durum L.) during early development and the temporal dynamics of denitrification and the nirK denitrifier communities. The impact of the presence of durum plants in the mesocosm experiment was relatively small, however, the presence of durum plants did modify the legacy effects of preceding crop and weediness on the denitrifier community. Differences in denitrifier community structure were due to differential presence/absence and differential abundance of multiple T-RFs. To our knowledge, this is the first study to investigate the effects of long-term weed management strategies on denitrification. Our results indicate that weediness contributes to priming effects and unexplained variation associated with these soil processes and that weed management history should be taken into consideration when determining soil function and soil microbial community dynamics in agricultural systems.

Densities of Eggs and Nymphs and Percent Parasitism of Bemisia tabaci (Hemiptera: Aleyrodidae) on Common Weeds in West Central Florida.

The density of eggs and nymphs of Bemisia tabaci (Gennadius) biotype B and the percent parasitism of the nymphs were measured from specimens collected on nine species of weeds, commonly found in west central Florida during the spring and summer of 2012 and 2013. The weeds were direct seeded in 2012 and grown as transplants in 2013 for Randomized Complete Block design experiments. The leaf area of each whole-plant sample was measured and the B. tabaci density parameters were converted to numbers per 100 cm2. In June and July, 2013, whole-plant samples became too large to examine entirely, thus a representative portion of a plant totaling about 1000 cm2 was sampled. Egg and nymph densities and percent parasitism varied greatly among weed species, and were higher overall in 2012 than in 2013. The highest densities of eggs and nymphs were measured on Abutilon theophrasti, Cassia obtusifolia and Emilia fosbergii each year. Lower densities of immature B. tabaci were measured on most dates for Amaranthus retroflexus, Bidens alba, Ipomoea lacunosa, Sesbania exaltata and Sida acuta. Nymph to egg ratios of 1:4 were observed on A. theophrasti and S. exaltata in 2012, while less than one nymph per ten eggs was observed overall on A. retroflexus, E. fosbergii and I. lacunosa. In 2012, parasitism rates of 32.3% were measured for B. alba, 23.4% for C. obtusifolia and 17.5% for S. acuta. Of the 206 parasitoids reared out over two seasons, 96.6% were Encarsia spp. and the remainder Eretmocerus spp. The role of weeds in managing B. tabaci is discussed.

Reinforcement learning-based design of sampling policies under cost constraints in Markov random fields: Application to weed map reconstruction

Weeds are responsible for yield losses in arable fields, whereas the role of weeds in agro-ecosystem food webs and in providing ecological services has been well established. Innovative weed management policies have to be designed to handle this trade-off between production and regulation services. As a consequence, there has been a growing interest in the study of the spatial distribution of weeds in crops, as a prerequisite to management. Such studies are usually based on maps of weed species. The issues involved in building probabilistic models of spatial processes as well as plausible maps of the process on the basis of models and observed data are frequently encountered and important. As important is the question of designing optimal sampling policies that make it possible to build maps of high probability when the model is known. This optimization problem is more complex to solve than the pure reconstruction problem and cannot generally be solved exactly. A generic approach to spatial sampling for optimizing map construction, based on Markov Random Fields (MRF), is provided and applied to the problem of weed sampling for mapping. MRF offer a powerful representation for reasoning on large sets of random variables in interaction. In the field of spatial statistics, the design of sampling policies has been largely studied in the case of continuous variables, using tools from the geostatistics domain. In the MRF case with finite state space variables, some heuristics have been proposed for the design problem but no universally accepted solution exists, particularly when considering adaptive policies as opposed to static ones. The problem of designing an adaptive sampling policy in an MRF can be formalized as an optimization problem. By combining tools from the fields of Artificial Intelligence (AI) and Computational Statistics, an original algorithm is then proposed for approximate resolution. This generic procedure, referred to as Least-Squares Dynamic Programming (LSDP), combines an approximation of the value of a sampling policy based on a linear regression, the construction of a batch of MRF realizations and a backwards induction algorithm. Based on an empirical comparison of the performance of LSDP with existing one-step-look-ahead sampling heuristics and solutions provided by classical AI algorithms, the following conclusions can be derived: (i) a naïve heuristic consisting of sampling sites where marginals are the most uncertain is already an efficient sampling approach; (ii) LSDP outperforms all the classical approaches we have tested; and (iii) LSDP outperforms the naïve heuristic approach in cases where sampling costs are not uniform over the set of variables or where sampling actions are constrained.

Does Integrated Weed Management affect the risk of crop diseases? A simulation case study with blackgrass weed and take-all disease

Integrated Weed Management (IWM) is necessary to reduce environmental damages by herbicides. The modifications required for IWM in cropping systems can result in unexpected side-effects, e.g. an increased risk of bioagressors other than weeds, either because the new cropping systems favour these bioagressors or because they favour weeds that are potential bioagressor hosts, thus increasing the contagion risk for crops. To evaluate these risks, the present case study worked with two model pests, a grass-weed species (blackgrass, Alopecurus myosuroides Huds.) and a soil-borne cereal pathogen (Gaeummanomyces graminis (Sacc.) von Arx et Olivier var. tritici Walker, responsible for take-all disease) which strongly interact and depend on cropping systems. For each pest, a model quantifying the effects of cropping systems in interaction with pedoclimatic conditions on pest dynamics was chosen from literature (AlomySys for weed dynamics, TakeAllSys for disease incidence) and linked with a new interaction model predicting the effect of one bioagressor on the other. A simulation study was then carried out, testing a herbicide-intensive reference system identified in farm surveys and a series of IWM systems combining several modifications (e.g. mouldboard ploughing, mechanical weeding, delayed sowing) to compensate for herbicide reductions. Each scenario was simulated over 27 years and repeated 20 times, with randomly chosen weather series from two different pedoclimates. The best IWM systems were more efficient than the herbicide-intensive reference system to control the grass weed. In the case of weed-free simulations, none of the IWM systems increased disease incidence, and the best systems even slightly reduced it. Integrating the reduction in weed seed production due to the disease in the simulations did not significantly change the simulation outcome, irrespective of the tested cropping system. Conversely, when the role of weed in disease transmission was taken into account, disease incidence in cereals crops considerably increased, particularly when past non-host crops in the rotation were infested by the weed. Nevertheless, the best IWM systems presented negligible weed-induced disease increase. The present results can be extrapolated to similar pest types (e.g. with propagules surviving in soil and negligible dispersal between fields). The modelling and simulation approach were easily feasible thanks to the availability of consistent models of cropping system effects on the two pests and experimental data on their interaction.

Responses of the specialist biological control agent, Aleochara bilineata, to vegetational diversity in canola agroecosystems

Plant biodiversity is known to affect insect populations, both herbivores and their natural enemies, and as a consequence, habitat management through increased plant species composition and abundance can be exploited for sustainable pest management. In agroecosystems where crop monocultures are the routine production practice, plant biodiversity can be increased by maintaining small populations of weeds, with potential beneficial effects arising from concomitant increases in the abundance of predator and parasitoid populations. We manipulated weed populations in both species of canola, Brassica rapa L. and Brassica napus L., to investigate responses of adults of Aleochara bilineata Gyllenhal (Coleoptera: Staphylinidae), an important natural enemy of root maggots ( Delia spp., Diptera: Anthomyiidae). Larval root maggots feed on canola taproots, disrupting the flow of water and nutrients within the plants, causing substantial yield reductions. Aleochara bilineata is a predator–parasitoid that attacks all root maggot pre-imaginal life stages. Activity density of A. bilineata increased as monocotyledonous weed biomass declined. Significant preferences between canola species were observed, with A. bilineata associated most frequently with B. rapa compared with B. napus. Our research suggests that improved management of root maggot infestations in canola through enhancement of populations of the A. bilineata predator–parasitoid could be accomplished by reducing weed infestations; however, such recommendations should consider other predators in the system and the role of weeds in reducing root maggot oviposition and damage.

Crop and pasture response to climate change.

We review recent research of importance to understanding crop and pasture plant species response to climate change. Topics include plant response to elevated CO(2) concentration, interactions with climate change variables and air pollutants, impacts of increased climate variability and frequency of extreme events, the role of weeds and pests, disease and animal health, issues in biodiversity, and vulnerability of soil carbon pools. We critically analyze the links between fundamental knowledge at the plant and plot level and the additional socio-economic variables that determine actual production and trade of food at regional to global scales. We conclude by making recommendations for current and future research needs, with a focus on continued and improved integration of experimental and modeling efforts.