Do root-emitted volatile organic compounds attract wireworms?

in Communications in Agricultural and Applied Biological Sciences (in press)

Wireworms are the soil dwelling larvae of click beetles (Coleoptera: Elateridae). Their importance as crop pests increases since the efficient chemical means to control them cannot be considered anymore ... [more ▼]

Wireworms are the soil dwelling larvae of click beetles (Coleoptera: Elateridae). Their importance as crop pests increases since the efficient chemical means to control them cannot be considered anymore. Therefore, many integrated pest management strategies have been investigated in the past few years. Most of them rely on the understanding of the ecology of the click beetles during their whole life cycle. We focus our work on the chemical ecology of wireworms, more precisely on the root-emitted volatile organic compounds (VOCs) that might intervene in the food-searching process of the larvae by helping them to find a suitable host-plant or by acting as key factors in the belowground defence mechanism of the plant. Here, we present our first results of dual-choice orientation tests in olfactometric pipes. Wireworms (Agriotes sordidus Illiger) were submitted individually to a variety of olfactory baits ranging from entire barley roots (Hordeum vulgare L. var. Quench) to isolated VOCs identified as part of the emitting profile. The latter was described thanks to HS-SPME samplings and GC-MS analysis, for roots grown in the exact same conditions as for the olfactometric experimentations with entire roots. Most of the experimentations gave significant results. When confronted to volatiles emitted by entire roots, wireworms significantly orientated towards the bait (χ²-goodness-of-fit test, χ²=8, P-value=0.005). This result allowed us to follow up with the same device and to progressively vary the nature of the baits. Our protocol should be used for other plant-wireworm species combinations. Our results should be taken into account in varietal selection, in crop rotation, or in trapping systems aiming at the reduction of the populations of wireworms. [less ▲]

Long term measurements of volatile organic compounds exchanges above a maize field at Lonzee (Belgium)

in Communications in Agricultural and Applied Biological Sciences (2013, February), 78(1), 127-132

VOC (volatile organic compounds) include a wide set of molecules which are mostly emitted by the plants. Atmospheric scientists are strongly interested in these compounds because of their important role ... [more ▼]

VOC (volatile organic compounds) include a wide set of molecules which are mostly emitted by the plants. Atmospheric scientists are strongly interested in these compounds because of their important role in the atmospheric chemistry and their final impact on air pollution and climate change. Evaluation of current and future VOC emissions is thus necessary and requires a comprehensive understanding of VOC production and exchange dynamics under a wide panel of climatic conditions and ecosystems. Forest and non pastured grasslands have been largely studied for the last decade. However, knowledge about VOC fluxes from croplands remains scarce. Our study focuses on the VOC exchanges between a maize field and the atmosphere. It is incorporated in a wider project that aims to study VOC fluxes from two croplands (maize and winter wheat) and a pastured grassland. VOC fluxes have been measured on a maize field during the whole growing season using a micrometeorological method (eddy covariance). While first results show half-hourly bidirectionnal exchanges among all the preselected compounds, in average methanol stands for the greatest emitted VOC, followed by green leaf volatiles, and acetic acid is the greatest taken up VOC. Small isoprene and monoterpenes fluxes are also observed. A diurnal pattern is found for all those VOC, with greater emission/uptake during the day, suggesting a flux dependence on environmental parameters. These environmental controls will be further investigated [less ▲]

Development of an experimental device allowing plant-plant interaction studies and in situ dynamic trapping of volatile organic compounds emitted by barley (Hordeum distichon L.) roots

in Communications in Agricultural and Applied Biological Sciences (2013, February), 78(1), 97-102

In response to wounding or herbivore attack, leaves and roots of higher plants release volatile organic compounds (VOCs). To date, VOCs analysis and plant−plant interaction studies have been mainly ... [more ▼]

In response to wounding or herbivore attack, leaves and roots of higher plants release volatile organic compounds (VOCs). To date, VOCs analysis and plant−plant interaction studies have been mainly performed on aboveground plant tissues, leaving the roles played by root VOCs in plant−plant interaction unexplored. In this context, this project aims at setting up an original experimental device allowing both dynamic trapping of VOCs emitted by mechanically damaged H. distichon roots and the study of the roles played by root VOCs in intra and interspecific plant−plant interactions. The experimental device consists of Barley seedlings cultivated in closed PTFE reactors filled with wet sand. Before being analysed by gas chromatography−mass spectrometry, root VOCs are trapped via a dynamic system on Tenax cartridges using a charcoal-filtered and humidified air. Preliminary results show that 7 day-old wounded Barley roots emit C9 fatty acid derivatives (E-non-2-enal and nona-2,6-dienal) as major compounds, contrasting with aboveground plant tissues that mainly emit C6 alcohols, aldehydes, and their derivative esters. For plant−plant interaction studies, receiver plants are exposed to an airflow enriched with VOCs from root damaged Barley plants of the same age. [less ▲]

New insights on the role of root radial hydraulic conductivity in the overall water uptake process

in Communications in Agricultural and Applied Biological Sciences (2012), 77(1), 117--122

Study of the factors involved in the aggregation of Harmonia axyridis Pallas (Coleoptera : Coccinellidae)

in Communications in Agricultural and Applied Biological Sciences (2012), 77(1), 101-104

The aggregative behaviour of the multicoloured Asian ladybeetle, Harmonia axyridis Pallas, during winters, is still misunderstood. Our study was focused on the chemical and physical factors involved in ... [more ▼]

The aggregative behaviour of the multicoloured Asian ladybeetle, Harmonia axyridis Pallas, during winters, is still misunderstood. Our study was focused on the chemical and physical factors involved in the selection of its aggregation sites. Chemical and behavioural analyses highlighted that long-chain hydrocarbons lead congeners towards aggregations and ensure the cohesion of the cluster. On the other hand, we investigated the influence of (1) the density of individuals and (2) the quality of available shelters on H. axyridis decision to settle and aggregate under shelters. A binary choice experiment conducted in laboratory highlighted a permanent aggregative behaviour of H. axyridis, even during non-wintering conditions, and the existence of social interactions between individuals. [less ▲]

Dynamics of black-grass populations depending on the sowing time of winter wheat

in Communications in Agricultural and Applied Biological Sciences (2011, May 24), 76(3), 485-490

Currently, economic, agronomic and environmental concerns, lead to reduce use of herbicides. This reduction can be help by cultural measures like delay of the sowing date. Four sowing dates of winter ... [more ▼]

Currently, economic, agronomic and environmental concerns, lead to reduce use of herbicides. This reduction can be help by cultural measures like delay of the sowing date. Four sowing dates of winter wheat from 15th of October to 26th of November were tested. Dynamic of black-grass populations and their reproduction rate were assessed as well as dynamic of winter wheat for each date. Delay of sowing could significantly reduce reproduction rate of blac-grass. It was shwn that the emergence rate (pl/m²), but also number of ears per plant and number of seeds per ear of black-grass decreased significantly with the sowing date. This reproduction of seeds productioin already is from sixty per cent of a delay of two weeks sowing. [less ▲]

Detection of accase target-site resistant Alopecurus myosuroides huds (black-grass) in Belgian populations

in Communications in Agricultural and Applied Biological Sciences (2009, May 19)

Black-grass is a common grass weed, widely spread in Northern Europe and also in Belgium. For ages, it has been an increasing problem in industrial crops, especially winter cereals. The first case of ... [more ▼]

Black-grass is a common grass weed, widely spread in Northern Europe and also in Belgium. For ages, it has been an increasing problem in industrial crops, especially winter cereals. The first case of resistance in Belgium was reported in 1996 by Robert Bulcke (Eelen et al., 1996). Yet the resistance mechanism was not specified. Since then, no more information was published about the evolution Belgium, while research continued in the United Kingdom and in France. Moreover, during the last decade, progress in molecular biology allowed to highlight the mechanism of target-site resistance. A simple PCR method allows to detect the mutation conferring resistance to herbicide. After two years of resistance monitoring in Belgium, mostly in the Walloon part, some populations have been clearly identified as highly resistant to ACCase inhibitor. These populations have been tested by molecular biology so as to detect the single nucleotide polymorphism (SNP) involved in this case. The method employed was the Polymerase Chain Reaction Allele Specific Assays (PASA: Délye, 2002a) for the mutation Ile-1781-Leu that confers a target-site resistance to ACCase inhibitors. Those analyses were performed on plant material issued from bioassays, either in glasshouses or in Petri dishes. Leaves have been collected from plants which survived a fenoxaprop-P treatment applied in a glasshouse single dose assay. Seedlings from resistant populations grown in Petri dishes containing either fenoxaprop-P or cycloxydim provided the second type of sample. Ile1781 mutants were discovered within three populations. Each mutant plant was heterozygote. Five of those samples have been sequenced to confirm PASA results and everyone was matching. Moreover, they were all issued from Petri dishes containing cycloxydim, known to be unaffected by enhanced metabolism, confirming that theses populations are indeed target-site resistant. [less ▲]

Risks assessment of water pollution by pesticides at local scale (Pesteaux Project): study of polluting pressure

in Communications in Agricultural and Applied Biological Sciences (2009), 74(1), 165-170

Pollution of water resources (surface waters and ground waters) by pesticide uses is one of the key point of the European policy with the imptementation of the Water Frame Work Directive (2000/60/EC) and ... [more ▼]

Pollution of water resources (surface waters and ground waters) by pesticide uses is one of the key point of the European policy with the imptementation of the Water Frame Work Directive (2000/60/EC) and the thematic Strategy on the Sustainable use of pesticides. According to this Legislation, the Member States must initiale measures to limit environmental and toxicologieal effects caused by pesticide uses. The Agricultural Research Centre of Wallonia (CRA-W) emphasized the need of a toot for spatial risk analysis and develops it within the framework of PESTEAUX project. The originality of the approach proposed by the CRA-W is to generate maps to identify the risk of pollution at locale scale (agricultural parcel). The risk will be assessed according to the study of different factors, grouped under 3 data's tayers: polluting pressure, vulnerability of the physical environment (soil) and meteorological data. This approach is directly based on the risk's definition which takes into account the polluting pressure, linked te the human activities, and the vulnerabitity of the soil, defined by factors of physical environment which characterize the water flow in the parcel. Moreover, meteorological data influence the intensity and likelihoad flow of water, and indirectly pesticide by leaching or runoff. The PESTEAUX's approach to study the pollution is based on the model "source-vector-target". The source is the polluting pressure, in other words, the pesticides which could reach the targets. The main vector is the water which vehicles the pesticide on and trough the soil until the target which are the surface waters or ground waters. ln this paper we introduce the factors contributing to the polluting pressure. These factors are linking to the human activities and more precisely, to the pesticide uses. The factors considered have an influence on pesticide's transport by water (in its solid state or in dissolved state by leaching, run-off, or erosion) but also on a set of process controlling pesticide behavior in the environment such as degradation, sorption, .... [less ▲]

Investigation of carbohydrate binding property of a fungal lectin from Xerocomus chrysenteron and potential use on Myzus persicae aphid.

in Communications in Agricultural and Applied Biological Sciences (2008), 73(3), 629-38

In recent years encoding insecticidal Lectins have been suggested as one of the promising methods against insect pests and have been engineered successfully into a variety of crops including wheat, rice ... [more ▼]

In recent years encoding insecticidal Lectins have been suggested as one of the promising methods against insect pests and have been engineered successfully into a variety of crops including wheat, rice, tobacco and potatoes. Xerocomus chrysenteron Lectin (XCL) has a high hemagglutinating activity and results obtained from sugar specificity assay showed to have specific affinity to Galactose and N-Acetylgalactosamine (GalNAc). In previous studies, XCL was shown to have negative effects on some insect pests, including aphids. In the present study, the effects of different carbohydrates including D-glucose, D-mannose, D-galactose and GalNAc, associated with 0.1% XCL (w/v) in artificial diet was investigated to assess the evolution of the lectin toxicity toward Myzus persicae aphid during 7 days. M. persicae, a polyphagous aphid, showed no significant differences of mortality when fed with the XCL lectin associated with Glucose and Mannose or fed on XCL diet only. At the opposite, the mortality rates related to artificial diet supplemented with Galactose or GalNAc and XCL were significantly reduced. There was then a significant mortality difference between M. persicae fed on an artificial diet incorporated specific carbohydrate binding Lectin with those fed with lectin only. The potential use of this particular fungal Lectin (XCL) with more specific carbohydrate binding will be discussed in relation to the development of bio-insecticide and integrated pest management. [less ▲]

How does the age of hoverfly females affect their reproduction?

in Communications in Agricultural and Applied Biological Sciences (2007), 72(3),