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IOBC-WPRS Bulletin Vol. 92, 2013

 

IOBC-WPRS Bulletin Vol. 92, 2013

Working Group "Integrated Control in Oilseed Crops".
Proceedings of the meeting at FIAP, Paris (France), 29 September - 01 October, 2008.
Editors: Birger Koopmann, Samantha Cook, Neal Evans and Bernd Ulber.
ISBN 978-92-9067-271-5 [XIII + 218 pp.]

 

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European network for the durable exploitation of crop protection strategies (ENDURE)
Neal Evans, Colin H. Denholm, Ian Denholm and Lise Nistrup Jørgensen

Abstract: The overall objective of this Network of Excellence (acronym ENDURE) is to reshape European research and development on pesticide use in crops and establish Europe as a leader in the development and implementation of sustainable pest management strategies. ENDURE aims to create a coordinated structure that takes advantage of alternative technologies, build on advances and complementary expertise in agricultural sciences, ecology, behaviour, genetics, economics and social sciences, and connect researchers to other stakeholders in extension, industry, policy-making and society at large. This multi-disciplinary and cross-sector approach is designed to foster the development and implementation of strategies rationalising and reducing pesticide inputs as well as reducing the associated risks. The specific goals of ENDURE are to integrate research capacity and resources currently fragmented across Europe, to enhance the research-to-R&D innovation process by creating working relationships between researchers and practitioners in extension and farming, to engage with industry, policy-makers and civil society to help define the research agenda, and to pass on knowledge, know-how and resources through training, education, and dissemination.

3-6

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Utilization of a model to re-design integrated crop management for winter oilseed rape
Muriel Valantin-Morison, Stéphane Lemarié, Jean-Noel Aubertot, Gilles Grandeau Raymond Reau and Anne Lacroix

Abstract: Concerns about the adverse impacts of pesticides on the environment and their inevitable negative side-effects on non-target organisms have been growing since the 1960’s. As a consequence, regulatory bodies take into account the environmental effects of pesticide applications, leading to increased restrictions in their use or to their revocation or banning (van der Werf, 1996). For winter oilseed rape (Brassica napus L.) in France, herbicides, fungicides and insecticides constitute the largest component of variable operating costs: representing 20% of the gross margin. On the other hand, in order to avoid disease occurrence, weed infestation and pest attack, diverse elementary control methods (genetic, cultural, mechanical, chemical) can be used in integrated pest management strategies (Dhaliwal et al., 2004, El Titi et al., 1993). Since each technical operation is likely to modify the sanitary status of a crop, it is therefore possible to design cropping systems to minimize crop loss induced by pest population with a limited use of chemical control. Because of the complexity of the considered systems due to interactions between cultural practices, crop status, soil, climate and pest populations, modelling is a key tool to propose innovative cropping systems less vulnerable to pests. Several experiments (1994-2004) have been used to analyze and simulate (i) the effects of agricultural practices on the pests and their interaction with the crop and (ii) the yield losses induced by pests. A bio-economic model, named OMEGA sys, has been developed in order to represent the effects of crop management either on crop yield, weed biomass and stem cancer attacks. The first aim of this model is to help in building environmental friendly crop management systems. The inputs of the model are climatic variables and the combination of each element of crop management, while the outputs are potential, attainable yield, number of pesticide treatments and gross margin. An algorithm of gross margin optimization is combined to the agronomic model in order to rank the diverse combinations of crop practices. This paper makes a short description of the OMEGA sys, gives some results of assessments and illustrates the new integrated crop management strategies than can be obtained with such methodology in two agronomical contexts and with two weed/disease pressures. Depending of the economic scenario, the first crop management strategy selected by the OMEGA sys are characterized by no or few pesticides utilization. The best crop management systems selected are different between the different agronomic context (soil, preceding crop and weed pressure).

7-18

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Nitrogen fertilisation of winter oilseed rape: impact on insect pests, their parasitoids and plant diseases
Eve Veromann, Merje Toome, Maris Saarniit, Lea Narits and Anne Luik

Abstract: Nitrogen fertilisation is essential for maximized oilseed rape yields. However, very little is known about the impact of fertilisation on insect pests and diseases. We studied the impact of additional nitrogen on winter oilseed rape pod number, disease abundance and the oviposition activity of the insect pests Meligethes aeneus and Ceutorhynchus assimilis and their parasitoids. Insect sampling, pod counts and disease assessments were carried out on plots with seven different N-fertilizer levels (0, 60, 80, 100, 120, 140 and 160 kg/ha). Fertilisation increased significantly the number of pods and decreased the disease scores of the most severe plant disease Alternaria brassicae. There was no clear correlation between fertilisation and insect damage. The least preferred plants for M. aeneus were in plots with 140 kg/ha and with no additional nitrogen fertilisation. There was no significant difference between plots in the number of damaged pods caused by C. assimilis. The parasitation rate of M. aeneus was low whereas C. assimilis larvae were 100% parasitizised. This study showed that intermediate nitrogen fertilisation did not attract more insect pests but was favourable to parasitoids and might even reduce disease problems, such as dark pod spot.

19-29

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Orobanche ramosa on winter oilseed rape in France: risks and perspectives of control
Phillippe Simier, Christian Boulet, Delphine Pineault, Régine Delourme, Martine Leflon and Phillippe Delavault

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31

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Accessing slug risk and slug control in oilseed rape
Dinka Grubišić, Tanja Gotlin Čuljak and Siniša Jelovčan

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32

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The effect of seed treatment on growth and development of oilseed rape
Sinisa Jelovcan, Tanja Gotlin Culjak, Wolfgang Büchs and Dinka Grubisic

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33

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The potential of entomopathogenic fungi Beauveria bassiana (Bals.) Vuillemin and Metarhizium anisopliae (Metschinkoff) Sorokin to control Helicoverpa armigera (Hübner) on sunflower
Waqas Wakil, M. Usman Ghazanfar and Y. J. Kwon

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37

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The effect of fertilizers on the pests in oilseed rape
Tanja Gotlin Culjak, Sinisa Jelovcan, Wolfgang Büchs and Dinka Grubisic

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38

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Effect of nitrogen fertilization, cultivar and species on incidence of two major pests of winter oilseed rape (Brassica napus L.): the pollen beetle (Meligethes aeneus F.) and the stem weevil (Ceutorhynchus napi Gyl.)
Adrien Rusch and Muriel Valantin-Morison

Abstract: Pollen beetle and stem weevil are among the most important insect pests in winter oilseed rape crops (WOSR). Moreover recent monitoring programs have shown the important development of metabolic resistance to pyrethroïds resulting in inefficient insecticide treatments. A better comprehension of the relationships between crop management and pest damage has been investigated in order to adapt new control strategies. To understand the effects of crop management, we measured population dynamics and damage caused by both pollen beetles and stem weevils on a split plot testing three nitrogen supply levels and two cultivars as main factors. Plant species effects were investigated in an experimental trial of winter oilseed rape with turnip rape borders. A cultivar with high isothiocyanate concentrations was more attractive than a cultivar with low isothiocyanate concentrations. Crop attractiveness is function of nitrogen supply and its effect on different crop variables. Indeed, stem weevil selects its host plants at stem elongation and is affected by crop height, whereas pollen beetle is sensible to dry weight. Furthermore a major role of growth stage development on host selection was found: the more advanced stages were the more colonized. These effects have not been previously reported at field level. Our results confirmed a high attractiveness of the turnip rape due to growth stage. No effect of nitrogen supply and cultivar was reported on the number of damaged buds. However, clear effects of nitrogen on stem weevil damage were recorded. Nitrogen fertilization interacts with pollen beetle damage by compensation mechanisms principally acting on seed weight. Compensation capacities are determined by time and rates of nitrogen applications and by pest population dynamics. These results bring new challenges for crop management, particularly for organic crops, by trap crop strategies and adapted nitrogen applications.

39-44

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Phenologies and diel periodicities of within-crop flight by pests and parasitoids in winter oilseed rape in the UK
Andrew W. Ferguson, Ross Holdgate, Neil S. Mason, Suzanne J. Clark and Ingrid H. Williams

Abstract: Parasitoids are important natural enemies of insect pests of oilseed rape (Brassica napus) in Europe yet they are vulnerable to effects of insecticides. Temporal targeting of insecticide against the cabbage seed weevil (Ceutorhynchus obstrictus, syn. C. assimilis) reduces harm to its parasitoids and so benefits conservation biological control. The objective of this study was to establish whether the same principle could be used to protect parasitoids of other pests when insecticides are applied during bud or flowering stages for control of pollen beetle (Meligethes aeneus) or cabbage seed weevil. Yellow water traps in a crop of winter oilseed rape were used to record the phenology of these pests and of three species of tersilochine parasitoids, Phradis interstitialis and Tersilochus heterocerus (both larval parasitoids of pollen beetle) and Tersilochus obscurator (a larval parasitoid of cabbage stem weevil, Ceutorhynchus pallidactylus). The diel within-crop flight periodicities of the pollen beetle and two tersilochine species were established using Malaise traps with automated time-sorting heads and were analysed in relation to meteorological data. None of the parasitoids were active in the crop at bud stage and they would therefore not be at risk from insecticides applied at this recommended time for pollen beetle control. However, all three species were active in the crop at mid-flowering and therefore potentially at risk from insecticides applied for seed weevil control. Peak flight activity of the pollen beetle, T. obscurator and P. interstitialis was around midday and the pollen beetle and T. obscurator showed marked diel periodicity. Flight activity was positively correlated with solar energy and average air temperature and weakly negatively correlated with wind speed. Few insects were caught before 10.00 h. The difficulty of defining days when insecticide applications do not risk significant injury to parasitoids is discussed. It is suggested that parasitoids present in the crop might be less at risk from selective insecticides if applied a times of day when the insects are not flying and that this is worthy of further investigation.

45-54

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Mortality factors of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Coleoptera, Curculionidae) in Europe
Tim Haye and Ulli Kuhlmann

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57

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The effectiveness of parasitoids in controlling the population size of Ceutorhynchus assimilis (Payk.) (Coleoptera: Curculionidae; syn. C. obstrictus) in winter oilseed rape
Eve Veromann and Anne Luik

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58

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Influence of insecticide application on host finding of the cabbage stem weevil parasitoid Tersilochus obscurator (Hym.; Ichneumonidae)
Nadine Neumann, Stefan Schütz, Ulrike Eisenwiener and Bernd Ulber

Abstract: Host location of hymenopterous parasitoids is mainly based on olfactory cues emitted from the infested host plant or host larvae. In this study, we used behavioural bioassays to determine sub-lethal effects of insecticide residues on host finding of Tersilochus obscurator (Hym.; Ichneumonidae), a specialist parasitoid of the larvae of cabbage stem weevil, Ceutorhynchus pallidactylus (Mrsh.) that feeds within petioles and stems of oilseed rape. In Y-tube olfactometer experiments, T. obscurator females significantly preferred volatiles emitted from untreated leaves to volatiles emitted from leaves treated with the neonicotinoid insecticide thiacloprid, but not to volatiles emitted from leaves treated with the pyrethroid lambda-cyhalothrin. In dual-choice experiments females spent less time foraging on insecticide-treated leaves compared to untreated leaves or even avoided treated leaves. Further, on insecticide-treated leaves they performed less ovipositor probes than on untreated leaves. Thus, sub-lethal effects of insecticides may substantially reduce the level of parasitism of oilseed rape pests in the field.

59-61

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Effect on Ceutorhynchus pallidactylus abundance and damage of insecticide type and timing of treatment based on phenology of female imigration into oilseed rape crops
Marek Seidenglanz and Jana Poslušná

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62

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Using molecular methods to study pollen beetles: distribution and predation
Barbara Ekbom

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65

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Resistance of pollen beetle (Meligethes aeneus F.) to pyrethroids – results of a national monitoring in Luxembourg
Michael Eickermann, Philippe Delfosse, Jean-François Hausman and Lucien Hoffmann

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66

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First results of the monitoring of the resistant pollen beetles (Meligethes aeneus Fabricius 1775) occurrence in the Czech Republic
Marek Seidenglanz, Jana Poslušná, Jiří Rotrekl, Pavel Kolařík, Jiří Havel and Eva Hrudová

Abstract: Laboratory experiments were conducted to test effects of the active substances of two different pyrethroids on imagos of the pollen beetle (Meligethes aeneus Fabricius 1775) collected in various areas of the Czech Republic in 2008. The tested pyrethroids were: lambda-cyhalothrin as a specimen of the ester pyrethroids (type II) and etofenprox as a specimen of the other group of pyrethroids (type I, ether pyrethroids). An adult-vial-test (IRAC Susceptibility Test Method No. 11) was used.
The pyrethroids were applied in the glass tubes (internal surface area: 37.97 cm2). The lambda-cyhalothrin was applied as four doses: 0 μg cm-2 (acetone only); 0.003 μg cm-2 (4% of the European field application rate of 7.5 g a.i. ha-1); 0.015 μg cm-2 (20% rate); 0.075 μg cm-2 (100% rate). The etofenprox was also applied as four doses:
0 μg cm-2 (acetone only); 0.016 μg cm-2 (4% of the Czech field application rate of 40 g a.i. ha-1); 0.080 μg cm-2 (20% rate); 0.400 μg cm-2 (100% rate). The collected insects were exposed to the dried residues of the insecticides for up to 24 hours. The response of beetles were assigned into one of four categories in accordance to their reactions to the insecticidal residues after 1, 5 and after 24 hours from the beginning of the tests. The active imagos without any symptoms of insecticide affect were assigned to category 4, imagos with slight symptoms (retained ability to move the legs) were assigned to category 3, severely affected beetles (immobility, tremor) were assigned to category 2 and dead imagos were assigned to category 1.
Significant differences were found among the reactions of the pollen beetles originating from the compared localities to lambda-cyhalothrin applied at the 100% rate. The differences in the lambda-cyhalothrin effectiveness expressed in accordance to Abbott exceeded 50% among the different localities. Conversely, there were no significant differences between the reactions of the pollen beetles originating from the five compared localities to the etofenprox applied at the 100% rate. The differences in the etofenprox effectiveness expressed in accordance with Abbott (and in the pollen beetles mortalities) were minor between the compared localities. On the base of other analyses, it is also possible to conclude that the localities where the beetles showed significantly different reactions.

67-76

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Do insecticide resistant pollen beetles suffer a higher mortality during hibernation?
Thomas Thieme, Kai Gloyna and Uwe Drbal

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77

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Phenotypic search for promising entomopathogenic fungal isolates to control pollen beetles
Stefan Kuske, Christina Pilz and Ursula Kölliker-Ott

Abstract: Twenty five isolates of entomopathogenic fungi belonging to the species Beauveria bassiana (Balsamo) Vuillemin (21), B. brongniartii (Saccardo) Petch (2), Paecilomyces fumosoroseus (Wize) (1) and Metarhizium anisopliae Sorokin (1) were screened for virulence against pollen beetle Meligethes aeneus. Several of the selected B. bassiana isolates originated from naturally infected pollen beetles collected in Switzerland. For the laboratory bioassays adult pollen beetles were dipped into a conidial suspension of 1 x 107 spores per ml (0,05% Tween 80) and incubated at 22 °C, 70% rh, L:D 16:8. Infection rates were recorded after 15 days. Seven isolates of B. bassiana as well as the P. fumosoroseus isolate achieved infection rates of ≥ 67%. Twelve isolates caused intermediate infection rates of 34-66%, whereas five B. bassiana isolates showed infection rates of less than 33%.

79-81

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Effect of tillage system and larval parasitism on pollen beetle (Meligethes spp.) populations
Bernd Ulber and Claudia Schierbaum-Schickler

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83

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Role of architectural plasticity in the response of oilseed rape to flower pruning, simulating damage by pollen beetles (Meligethes aeneus)
Amélie Pinet, Alexandra Jullien, Jean-Michelle Allirand and Bertrand Ney

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84

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Effect of sowing date on health status of open pollinated, composite hybrid and restored hybrid cultivars of winter oilseed rape (Brassica napus L.)
Dariusz Panka, Czeslaw Sadowski and Leszek Lenc

Abstract: The aim of the study was to evaluate the effect of sowing date on the growth and development of the open pollinated (‘Contact’), composite hybrid (‘Kaszub’) and restored hybrid (‘Kronos’) cultivars of winter oilseed rape. Higher degree of blackleg (Leptosphaeria maculans, L. biglobosa) and black spot (Alternaria spp.) symptoms were observed during the three years of investigations. Trace symptoms of infection with Erysiphe cruciferarum, Sclerotinia sclerotiorum and Botrytis cinerea were also noted. The occurrence of blackleg on winter oilseed rape was influenced by both experimental factors investigated. Significantly lower levels of infection of Leptosphaeria spp. were noted in optimal and late sown crops. Significantly, in each year of research, the cultivar with lowest levels of blackleg was ‘Kaszub’. ‘Kronos’ the restored hybrid cultivar was significantly less susceptible to infection and the cultivar with the highest levels of blackleg was ‘Contact’, the open pollinated winter oilseed rape cultivar. There was no effect of the studied factors on black spot occurrence on any of the cultivars.

87-91

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Phenotypic distortions of winter rapeseed in successive generations after primary infection with phytoplasmas
Michał Starzycki, Elżbieta Starzycka and Jan Pszczoła

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92

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Pathogenic mycobiota of rape in Belarus
Valiantsina Aheichyk

Abstract: In the article the specific composition of winter and spring rape fungal diseases in Belarus was presented. 16 fungal species: Alternaria brassicae Sacc, A. brassicicola Wilts, A. alternata (Fr.) Keissler; Sclerotinia sclerotiorum (Lib.) de Bary; Sclerotinia trifoliorum Eriksson; Fusarium oxysporum f. sp. brassicae (Schlecht.) Snyd. et Hans.; Fusarium avenaceum (Fr.) Sacc.; Fusarium nivale (Fr.); Typhula incarnata Jasch. ex Fr.; Erysiphe cruciferarum Oxiz. et Junell; Phoma lingam (Tode) Desm.; Cylindrosporium concentricum Grev.; Botrytis cinerea (Fr.); Olpidium brassicae (Wor.) Dang; Pythium spp. were revealed and identified.
The symptomatology and forms of disease manifestation were described. Their spread and harmfulness was determined. The most economically important oilseed rape diseases in Belarus were identified as Alternaria blight, Sclerotinia stem rot, Fusarium wilt and gray mould.

93-95

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First occurrence of ring spot (Mycosphaerella brassicicola) in France
Annette Penaud, Jean-Pierre Palleau, Pascal Fauvin and Franck Duroueix

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96

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Potential impact of a changing climate on Phoma stem canker and light leaf spot of oilseed rape in the UK
Neal Evans, Bruce D. L. Fitt, Peter Gladders, Yong-Ju Huang and Jon S. West

Abstract: Phoma stem canker (Leptosphaeria maculans) and light leaf spot (Pyrenopeziza brassicae) are the two most serious diseases of winter oilseed rape in the UK. Despite expenditure of more than £20M on fungicides each growing season, these two major diseases account for more than £120M of losses (at a price of £225 t-1 ). The distribution of each disease is affected by climate, with Phoma stem canker most severe in the warmer, drier south and east of the UK and light leaf spot most severe in the wetter, cooler west and north with epidemics being particularly severe in Scotland. Little work has been done to predict the impacts of climate change on plant disease epidemics. To investigate possible impacts, a weather-based disease forecasting model for Phoma stem canker was combined with a climate change model predicting UK temperature and rainfall under high and low CO2 emissions for the 2020s and 2050s. Multi-site data collected over a 15-year period from across the UK were used to develop and validate the model to forecast the severity of epidemics on oilseed rape. The model predicted that Phoma stem canker epidemics will increase in severity and the range of the disease will spread northwards into Scotland by the 2020s. However, using the same climate change scenarios, a weather-based light leaf spot forecast model predicted that light leaf spot will become less serious throughout the UK, especially in southern England.
Crop protection and resistance to these two major UK pathogens make important contributions to climate change mitigation, since low-yielding diseased crops use more nitrogen fertilizer per ton of grain and require more crop-area to achieve the same national yield of oilseed rape. This work suggests that predictions of impacts of climate change on other plant diseases are needed to guide policy and practice in adapting to impacts of climate change on food security, environment and wildlife.

97-103

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Detecting airborne inoculum to forecast oilseed rape diseases
Jon S. West, Simon D. Atkins, Alastair McCartney, Neal Evans and Bruce D. L. Fitt

Abstract: Many fungal diseases of oilseed rape are caused by air-dispersed spores. The timing of spore release changes each season due to the weather because the maturation and release of spores is usually affected by moisture (rain, dew and relative humidity) and temperature. Most airborne spores are dispersed only short distances from a source but many others still travel long distances, although spore concentrations and viability in air reduces over time. Spore deposition results in individual disease foci when occurrence of viable inoculum and infection conditions are rare; as a gradient in a crop when a large number of spores are produced from a nearby source; or as a uniform infection when there is a large but distant source or multiple local sources of inoculum. Epidemics of common monocyclic diseases of widespread crops, such as Phoma stem canker and Sclerotinia stem rot of oilseed rape are usually initiated by airborne spores produced either a long distance from the crop or from multiple sites throughout a region. Therefore it should be possible to predict such epidemics regionally using suitably located spore samplers in order to enhance integrated disease control methods. Appropriate DNA-based diagnostic methods can be integrated with many different types of air samplers and are now providing new information about species that previously could not be identified accurately by visual microscopy methods. For example, a new diagnostic for Sclerotinia sclerotiorum (Rogers et al., 2008) has shown potential for warning of the presence of airborne inoculum. Furthermore, where reliable climate-based disease forecasts have been developed (e.g for Leptosphaeria maculans), air sampling integrated with DNA-based diagnostics can also provide useful information at the sub-species level, to monitor populations for traits such as the development of fungicide resistance (in a similar way to that found with strobilurin resistance in Mycosphaerella graminicola (Fraaije et al., 2005) or changes to the pathogen race-structure in response to deployment of resistant cultivars. The optimal location of air samplers depends on how widespread the host crop is and how common the pathogen is, since air samples, particularly at ground level are heavily weighted in favour of spore types produced nearby. Further work is required to investigate the spatial variability in spore numbers in air at different sites; how changes in numbers of airborne spores at particular heights above or distances away from crops are related to subsequent regional disease severity; and to develop methods to analyse samples and disseminate results rapidly.

105-109

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Impact of cabbage root fly, Delia radicum, on infections of oilseed rape by Verticillium longisporum and Phoma lingam
Harald Keunecke, Bernd Ulber and Andreas von Tiedemann

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110

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Biocontrol of Sclerotinia sclerotiorum and Verticillium longisporum by the mycoparasite Microsphaeropsis ochracea
Martin Stadler, Haiko Brandes, Birger Koopmann and Andreas von Tiedemann

Abstract: Microsphaeropsis ochracea is a newly discovered mycoparasitic species of Coelomycetes that was first isolated in the 1990s from dead apple leaves originating from Canadian apple orchards (Bernier et al., 1996). By using M. ochracea in vitro and field experiments, it is possible to control Botrytis squamosa, Rhizoctonia solani and Venturia inaequalis (Carisse et al., 2000; 2001; 2006).
The antagonistic effect of M. ochracea against the oilseed rape pathogens Sclerotinia sclerotiorum and Verticillium longisporum was investigated in laboratory and field experiments. In laboratory investigations we showed that the germination rates of sclerotia and microsclerotia were reduced by M. ochracea treatments. Decrease of germination strongly depended on M. ochracea inoculum density, the incubation temperature and the duration of incubation. In order to check the effect of M. ochracea on the two oilseed rape pathogens under field conditions we designed two long-term field experiments under an oilseed rape monoculture and an oilseed rape – winter wheat rotation. M. ochracea was applied as a formulated product (2,5 x 109 spores/g) in autumn before sowing and in spring before the start of stem extension at application rates of 1 kg/ha and 2 kg/ha.
The results indicated lower infestations of rape plants with S. sclerotiorum in M. ochracea treated plots than in untreated plots.

113-118

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The influence of Trichoderma species on Leptosphaeria maculans and L. biglobosa growth on agar media and in oilseed rape plants
Adam Dawidziuk, Delfina Popiel and Małgorzata Jędryczka

Abstract: The ascomycetous fungi Leptosphaeria maculans and L. biglobosa cause stem canker of crucifers – one of the most damaging diseases of oilseed rape in Poland and worldwide. The pathogens are responsible for major yield losses, which can be economically significant especially in the areas of intensive rapeseed cultivation in Europe, Australia and Canada. The pathogens are observed every year, with a higher proportion of L. maculans in West Europe and predominance of L. biglobosa in Central and East Europe. The disease is controlled with chemical sprays applied mostly in autumn. At many locations and years one autumn spray is insufficient to fully control the disease. Recently, great efforts are undertaken to study the possibility of biological control using antagonistic and hyperparasitic fungal species. It is postulated to use their potential to combat plant pathogens and use these organisms in integrated pest management technologies to reduce the amount of pesticides introduced to environment.
The aim of this work was to examine possibilities of biological control of L. maculans and L. biglobosa using hyperparasites from the genus Trichoderma obtained from oilseed rape and yellow lupine plants as well as from soil. Tested isolates belonged to T. atroviride, T. hamatum, T. harzianum, T. koningii and T. longibrachiatum. The experiments were performed under laboratory conditions using dual cultures as well as under glasshouse conditions using oilseed rape plants.
Trichoderma isolates caused significant decrease of growth rate, especially of L. biglobosa. On the other hand L. maculans showed antibiosis activity and caused decreased growth rate of T. longibrachiatum. The species of Trichoderma differed in their hyperparasitic effects towards Leptosphaeria spp. The highest decrease of Leptosphaeria spp. growth rate was caused by T. atroviride. Covering of cotyledons with Trichoderma spores was proved to serve as protective treatment against Leptosphaeria species. The influence of isolates from oilseed rape was significantly greater than the one originating from lupine.

119-126

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SIPPOM-WOSR, Simulator for Integrated Pathogen POpulation Management: a tool to help design and evaluate sustainable strategies to control Phoma stem canker on winter oilseed rape at the regional scale
Elise Lô-Pelzer, Marie Boillot, Jean-Noel Aubertot, Lydia Bousset, Marie-Hélène Jeuffroy and XavierPinochet

Abstract: Phoma stem canker, also known as blackleg, is a major disease of oilseed rape. Among the different means to control the disease – chemical treatments, agronomic practices and plant genetic resistances – the use of resistant cultivars is the most efficient. Winter oilseed rape cultivars have two types of resistance to Phoma stem canker, either specific or quantitative. New specific resistances are extremely efficient but may lack durability. Combining genetic, cultural and chemical control methods at the multiple-years and regional scales could help contain Phoma stem canker and preserve the efficiency of specific resistances, while ensuring economic profit for farmers and satisfying the environmental and toxicological exigencies of Integrated Crop Management. Given the considered scales and the number of technical operations that have to be taken into account, it is highly difficult to test disease management strategies using traditional field experiments. A model has been developed to evaluate the agronomic, economic and environmental performances of spatially distributed cropping systems: SIPPOM-WOSR, a Simulator for Integrated Pathogen Population Management, for Winter OilSeed Rape. SIPPOM consists of 5 sub-models simulating i) primary inoculum production, ii) ascospore dispersal, iii) crop growth and attainable yield, iv) dynamics of pathogen population genetic structure, and v) infection and relative yield loss. The output variables are disease severity indices and the associated yield losses, actual yields, gross margins, energetic costs of cultural practices and Treatment Frequency Indices. It also calculates the genetic structure of pathogen populations depending on four evolutionary forces or genetic mechanisms: migration, selection, recombination, and the allele effect. A sensitivity analysis has been carried out to study the sensitivity of the sub-models to parameter variations. It showed that SIPPOM can be confidently used to rank contrasted integrated control strategies. The evaluation of each sub-model revealed correct predictive quality. A comparison between simulated and observed data during the loss of efficacy period – 1994 to 2000 – of the Rlm1 specific resistance gene in the centre of France was satisfactory. Nevertheless, the results underlined the interest of introducing virulence costs in SIPPOM. Further simulations were carried out on the 2004-2008 period to assess the behaviour of SIPPOM for realistic field spatial distributions and cropping systems. Results showed that the disease index calculation should be adjusted to improve SIPPOM’s predictive quality. After improvements, strategies minimising the severity of Phoma stem canker and the risk of specific resistance loss of efficacy will be simulated.

129-134

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The prediction of Leptosphaeria maculansL. biglobosa pseudothecial maturation in Poland
Adam Dawidziuk, Jean-Noel Aubertot, Joanna Kazmarek and Małgorzata Jędryczka

Abstract: The fungal pathogens Leptosphaeria maculans (Desm.) Ces. et de Not. and L. biglobosa Shoemaker & Brun are responsible for Phoma stem canker – the disease is regarded as the most damaging to oilseed rape (Brassica napus L.) worldwide. In Europe, rapeseed plants are mostly infected in the autumn by ascospores produced in pseudothecia. These fruiting bodies of the perfect stage are formed on dead stems of oilseed rape plants infected in a previous growing season. It was proved that fungicide treatments against these pathogens are more effective when applied during the period of mass ascospore release, which occurs after a rain event following a full pseudothecial maturation. The prediction of the rate of L. maculans and L. biglobosa fruiting body maturation is therefore an important information for the optimisation of agrotechnical and chemical practices in cultivation of oilseed rape. The prediction of L. maculans and L. biglobosa pseudothecial maturation in Poland was based on a 9 year dataset (1998-2006), comprising biological observations of fungal development and two basic weather data: mean daily temperature and rainfall, beginning at harvest time of the previous cropping season of oilseed rape. The study concerned 100 site-years with one experiment site per year between 1998 and 2003 and the average of 35.5 sites per year in the later period. From 1998 to 2006 weather data were collected at experiment locations. Since 2006 the average distance from data collection site to a weather station was 13.3 km. The prediction model for pseudothecia maturation hypothesises that the probability of pseudothecial maturation follows a Gaussian distribution, as a function of the number of cumulated days favourable for maturation. The parameterisation of the model led to the following values: minimum daily temperature = 6.0 °C; maximum daily temperature: 29.6 °C; minimum cumulated rainfall over a 12-day period = 4.0 mm and standard deviation of the number of days favourable required for pseudothecial maturation σFD =1.9 days. The efficiency of the model was greater than 0.77, which suggests that the model can be used in a decision support system.

135-141

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PCR-detection of fungal pathogens in winter oilseed rape and their survey in Czech Republic
Jana Mazakova, Miloslav Zouhar, Eva Plachka and Pavel Rysanek

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143

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Genetic determinism of quantitative resistance to Leptosphaeria maculans in WOSR
Christophe Jestin, Maryse Lode, Patrick Vallee, Claude Domin, Cyril Falentin, Raymonde1 Horvais, Solène Coedel, Maria J. Manzanares-Dauleux and Régine Delourme

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144

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Resistance durability of oilseed rape to blackleg assessed in multi-year field experiments
Hortense Brun, Anne-Laure Besnard, Magalie Ermel, Frédérique Eber, Xavier Pinochet, Anne-Marie Chèvre and Michel Renard

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145

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Are varietal asociations of Brassica napus a way to manage efficiently specific resistance genes to Leptosphaeria maculans?
Anne-Marie Chèvre, Frédérique Eber, Patrick Vallée, Jean-Claude Letanneur, Claude Domin, Lydia Bousset, Hortense Brun and Régine Delourme

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146

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Are leaf symptoms a way to check an increase of virulent populations on Rlm7 hybrids?
Xavier Pinochet, Marie Hélène Balesdent, Emmanuelle Pic, Hortense Brun and Julien Carpezat

Abstract: New genotypes of oilseed rape were recently introduced commercially in France. Their excellent resistance to blackleg (Leptosphaeria maculans) is mainly due to a new major resistance gene, Rlm7. Such varieties are potentially exposed to a resistance breakdown. The main objective of extension bodies is to promote the durable management of resistance and try to anticipate any possible breakdown. This objective necessitates being able to detect as early as possible the first step of the pathogen population switch towards virulence. Two ideas were developed for such an aim. Firstly, a comparison between leaf symptom density on cultivars having or not having the targeted specific resistance may be used as an indirect indicator of the increase of virulent isolates in the population. The second way was to directly check virulence profiles of the pathogen population. These two methods have been tested since autumn 2004 in the central region of France at fields located between Issoudun and St Florent sur Cher. The first approach appeared to work during the first two experimental years. Nevertheless, epidemics were too low during the last two years to allow us to make a clear conclusion. Virulence profiles were surveyed in this region and also in experimental fields in Versailles, Grignon and Rennes, from isolates sampled from leaf symptoms. The survey showed that AvrLm7 (avirulent) spores were able to produce leaf symptoms on Rlm7 varieties. However the leaf lesions were often smaller than those due to virulent isolates, with a huge variability of leaf symptom morphology, even on the same genotype, in the same field, under the same climate. Only a low number of isolates from Rlm7-leaf symptoms were identified asavrLm7 (virulent). These results underline the risk of overestimation of virulence allele frequencies based on foliar symptoms, the need for pedagogic documents and teaching sessions to help experimenter’s and local advisors to detect the beginning of resistance breakdown in a bio-vigilant approach, and the difficulties of doing such a survey with limited costs and limited sampling.

147-154

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Occurrence of different Phoma lingam pathotypes on oilseed rape cultivars with different resistance gene background
Siv Ahlers, Andreas von Tiedemann and Birger Koopmann

Abstract: In the frame of a field study related to the artificial improvement of Phoma disease pressure, we monitored the disease incidence and severity of Phoma lingam on a small set of cultivars at a location close to Göttingen, central Germany. Visual assessments were performed on leaves, stems and the root collar. Furthermore, isolations were taken from diseased tissues. Isolates were differentiated into pathotypes by the use of the cotyledon test using the differential set Lirabon, Quinta, Glacier, Jet Neuf, Doublol (all of them rlm7) and Caiman (Rlm7).
High disease incidences but moderate disease severities were recorded. Inoculated variants (conidia spraying, stubble deposition) showed no significant differences to controls. Control of Phoma stem canker by intense spraying of ERIA (ai: Difenoconazol, intervals of about 3 weeks) was always very effective and highly significant in all cultivars. Diseases severities displayed the superior field resistance of the Rlm7 cultivar Caiman compared to the other rlm7-cultivars tested.
Phoma isolations were performed from cultivars Caiman and Oase. A number of 279 single pycnidiospore and hyphal tip isolates were checked in a first screen on cotyledons of cv. Lirabon to differentiate L. maculans (virulent on cv. Lirabon) and L. biglobosa (avirulent on cv. Lirabon). About 52 % of isolates were assigned to L. maculans. Significantly more L. maculans isolates originated from cv. Oase. L. biglobosa was predominant on cv. Caiman (about 96%). Race differentiation showed that diversity of Phoma-pathotypes was higher on cv. Oase than Caiman. Among the isolates originated from cv. Oase there were 9 avr7-isolates (3.3%) showing the presence of avr7 isolates in central Germany without a history of cultivating Rlm7 varieties.

155-161

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Avirulence genes of Leptosphaeria maculans: diversity of mechanisms to become virulent and perspectives
Marie-Hélène Balesdent, Isabelle Fudal, Guillaume Daverdin, Francis Parlange, Lilian Gout and Thierry Rouxel

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162

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Characterization of specific resistances to Leptosphaeria maculans in recent winter oilseed rape (Brassica napus L.) commercial varieties
Marie-Hélène Balesdent and Xavier Pinochet

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163

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A duplex PCR to follow the frequencies of avirulence 1 and 4 alleles in field populations of Leptosphaeria maculans
Julien Carpezat, Marie Boillot, Xavier Pinochet and Emmanuelle Pic

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164

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Elicitors of Leptosphaeria maculans inducing resistance to blackleg in oilseed rape
Lenka Burketová, Vladimír Šašek, Lucie Lorková, Phuong Dinh Kim and Olga Valentová

Abstract: Compounds produced by L. maculans into various cultivation media were tested for their ability to induce defence gene expression by means of RT-qPCR and SAR by inoculation test. After removing toxins and other low molecular metabolites by dialysis, the medium was concentrated and subsequently subjected to fractionation by ionex chromatography. Separated fractions inducing PR1 expression were digested by trypsin. Tryptic hydrolysates lost their PR1-inducing activity, which indicates a protein nature of the efficient elicitors.

165-169

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Detection and quantification of airborne ascospores of Sclerotinia sclerotiorum by quantitative-PCR
Sarah L. Atkins, Simon D. Atkins, Akinwunmi O. Latunde-Dada, Jenna F. Stonard and Jon S. West

Abstract: A new SYBR-green quantitative PCR (qPCR) method was developed to quantify airborne inoculum of Sclerotinia sclerotiorum. This was tested on DNA extracted from spores deposited onto wax-coated plastic tapes, such as those used in Burkard (Hirst-type) spore traps and rotating-arm traps. A linear relationship between ascospore numbers and S. sclerotiorum DNA indicated a mean of 0.35 pg DNA per spore. The method could detect DNA representing as few as 2 ascospores. The technique was insensitive to DNA of the host plant, Brassica napus, and other plant pathogens, including S. minor, S. trifoliorum, Botrytis cinerea, Leptosphaeria maculans and Pyrenopeziza brassicae, and common airborne fungal genera such as Cladosporium and Penicillium. Specific quantification of S. sclerotiorum was achieved in the qPCR method by including a heating step to 79 °C to melt off any exogenous products such as primer dimers that would otherwise falsely contribute to the calculation of target DNA present. This step also eliminated products amplified from any DNA of B. cinerea, if present in the sample. The feasibility of using the method in disease forecasting schemes was tested using archived DNA from air samplers that operated at Rothamsted in April-May in three different seasons, which had contrasting Sclerotinia stem rot (SSR) epidemics; 2007 had a severe SSR epidemic in England and high numbers of airborne ascospores were trapped at Rothamsted; while both 2003 and 2004 had a very low incidence of SSR in England and low numbers of airborne ascospores trapped at Rothamsted. The severe SSR season of 2007 occurred throughout a large part of northern Europe and was not predicted in the UK by climate-based disease-forecasts. This study showed that there was no relationship between rainfall and numbers of airborne ascospores of S. sclerotiorum present at Rothamsted during the period of infection in the severe SSR season (2007). In addition to the example application tested in this study, the qPCR method reported here has potential to evaluate the presence and quantity of S. sclerotiorum in a wider range of environmental samples such as soil, seed or plant tissues such as petals or stems. In the case of airborne inoculum, further research is required to develop methods to rapidly apply the S. sclerotiorum-specific qPCR to air samples and to confirm that airborne inoculum is a reliable indicator of SSR risk by testing over a wider geographical range and number of growing seasons.

173-178

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Economic gains and Integrated Pest Management: An application to the Sclerotinia and the Canola crop
Stéphan Marette, Antoine Messéan, Annette Penaud, Xavier Pinochet and Laurent Ruck

Abstract: Agronomic experimental data are used for simulating some economic implications linked to an integrated pest management applied to Sclerotinia stem rot in France. This integrated pest management is a diagnostic test allowing farmers to reduce their fungicide application for canola. Profit estimations for farmers are used for determining whether or not farmers would adopt this integrated pest management. Before 2007, simulations show that the use of a Sclerotinia diagnostic test provides economic gains for farmers slightly lower than the common used practice of preventive spraying of fungicides. However, the canola price increased in 2007 makes the diagnostic test less attractive for farmers compared to the systematic fungicide application. Various political scenarios including a test subsidy or an insurance program linked to the diagnostic test are examined. We show that both instruments would lead to the use of the diagnostic test, even if, for the regulator, the test subsidy is less costly than the insurance program linked to the diagnostic test.

179-190

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Use of infection criteria from SkleroPro to identify infection events for Sclerotinia stem rot in England, 1991-2007
Peter Gladders, Julie A. Smith and Denise Ginsburg

Abstract: Stem rot (Sclerotinia sclerotiorum) has increased in importance in England recently, but risk assessment and decisions on fungicide use remain difficult for individual crops. Stem rot levels in winter oilseed rape in 2007 were the highest yet recorded and the most severe since 1991. This prompted an investigation of the factors affecting the development of the 2007 epidemic. Petal tests indicated that inoculum was present despite very low rainfall in the spring. Hourly weather data for the flowering periods in 2006 (a ‘non-epidemic’ year) and 2007 were collated from a range of metereological stations to represent the main areas of production. The number of periods during flowering that met the infection criteria used in SkleroPro (minimum of 23 h with relative humidity > 80% and temperature > 7 °C) were identified. Further comparisons of infection events were made between ADAS Rosemaund, Hereford (west) and ADAS Boxworth, Cambridge (east) for the years 1991-2007. The SkleroPro infection criteria were useful for identification of infection events and interpretation of fungicide experiments where sclerotinia inoculum was present. At ADAS Boxworth where little sclerotina developed in most years, inoculum was considered to be limiting. The development of more effective guidance for stem rot management will require quantification of inoculum and prediction of infection events.

191-198

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Evaluation of a decision making tool for controlling Sclerotinia stem rot in WOSR
Annette Penaud, Dominique Wagner, David Makowski and Laurent Ruck

Abstract: Sclerotinia stem rot is a major disease of oilseed rape in France. Severe yield losses usually occur two to three times per decade. For controlling the disease by spraying a fungicide only when it is needed CETIOM has improved and evaluated a diagnostic test based on a measured proportion of oilseed rape flowers infected by Sclerotinia sclerotiorum. The score of this test is used as a risk indicator. Receiver operating characteristic (ROC) curves are used to determine a decision threshold according to the sensitivity and specificity values. The threshold of 30% infected flowers generally leads to correct decisions except when disease pressure was too high, as in 2007.

199-204

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Monitoring the sensitivity of Sclerotinia sclerotiorum to fungicides
Annette Penaud, Annie Micoud, Jaques Moinard, Florent Remuson, Anne-Sophie Walker and Pierre Leroux

Abstract: Sclerotinia sclerotiorum isolates from oilseed rape are monitored every year for fungicide resistance. In the past, the use of carbendazim was very popular and led to a widespread resistance among S. sclerotiorum populations, especially in the oilseed rape cropping areas. Regarding dicarboximides (eg iprodione, vinclozoline or procymidone), very few resistant isolates have been detected in several French regions, not affecting field efficacy. These fungicides are no longer registered in France. For two years, new fungicides belonging to carboxamides and the DMI families have been registered to control this disease. Thus, determining S. sclerotiorum baseline sensitivity to these new compounds was necessary to manage sustainable use. A method based on mycelial growth on synthetic agar medium amended with a concentration of 2 mg/l was developed for boscalid, prothioconazole and metconazole. The methods allowed us to determine the sensitivity to boscalid of around 1400 field isolates; no resistance to boscalid was detected in 2007. The method was less reliable for DMI compounds.

205-209

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Fungicide application timing and control of Sclerotinia stem rot in England in 2007 and 2008
Faye Ritchie, Peter Gladders, Julie A. Smith and Steve Waterhouse

Abstract: Stem rot (Sclerotinia sclerotiorum) on winter oilseed rape has caused significant yield losses in the UK in 2007 and 2008. Industry-funded trials in the West Midlands investigated the effect of fungicides on stem rot control in 2007 and 2008. These trials demonstrated that the onset of infection and fungicide application timing to be significant factors in stem rot control in oilseed rape. In 2007, initial infection occurred in late April/early May whereas infection occurred in mid to late May in 2008. Fungicides applied in late April gave good early control of the epidemic in 2007. In contrast, in 2008, fungicides applied in late April did not control the epidemic as effectively as those applied in early May due to the later onset of the epidemic. In both years, the control of stem rot infection declined as the season progressed following a single mid-flower fungicide application. Strong fungicide protection persisted for about three weeks. The significance of these results on Sclerotinia control is discussed.

211-218

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