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IOBC-WPRS Bulletin Vol. 107, 2014


IOBC-WPRS Bulletin Vol. 107, 2014

Working Group "Integrated protection in Field Vegetables".
Proceedings of the meetings at Bäckaskogs slot (Sweden), 25 - 28 September, 2011 and
Bergerac (France), 23 - 25 September, 2013.
Edited by Richard Meadow.
ISBN 978-92-9067-288-3 [III + 217 pp.]


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Suitability of three different Brassicas as trap crops against flea beetles (Phyllotreta spp.) and cabbage stink bugs (Eurydema spp.) on white cabbage
Tanja Bohinc, Stanislav Trdan

Abstract: Numerous studies have examined the responses of pests to different cole crops. In this paper we would like to present results of a 2-year study (2009-2010) and its usefulness in sustainable agriculture. We evaluated the impact of three trap crops (oil radish, oil rape, and white mustard) as a protection method against cabbage stink bugs (Eurydema spp.) and flea beetles (Phyllotreta spp.) attack on two hybrids of white cabbage. The experiment was designed as randomized complete block with four treatments, each replicated 4 times. We can conclude that oil rape was the most efficient trap crop concerning damage caused by cabbage stink bugs. In 2010, we evaluated oil radish as the most susceptible to flea beetles, while they did not display specific preference to any of trap crops tested in 2009. Our research confirms the theory that the amount of glucosinolates varies among different plant species and also among different plant organs.


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Suitability of ‘old’ and ‘new’ cultivars of Brussels sprout as host plants for pest insects
Rosemary Collier, Huseyin Biyikoglu

Abstract: Six cultivars (two F1 hybrids, two open-pollinated and two landrace) of Brussels Sprout were grown in pots in four different types of compost containing different levels of fertilisers. The plants were infested with known numbers of the immature stages of pest insects in three separate experiments (Brevicoryne brassicae, Plutella xylostella, Delia radicum respectively) to determine their suitability as host plants. The results indicated that the landrace cultivars were the least suitable hosts for Brevicoryne brassicae and Delia radicum but fertiliser treatment appeared to have little effect on these species. In contrast, numbers of Plutella xylostella were associated with fertiliser treatment but there was no differential effect of cultivar. Most Plutella xylostella were recovered from plants grown in the compost with no added fertiliser. There were no statistically-significant cultivar x fertiliser interactions.


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Influence of companion plant architecture on oviposition by female cabbage root flies (Delia radicum)
on cauliflower host plants

Rosemary Collier, Marian Elliott

Abstract: Many researchers have shown that the numbers of pest insects found on cruciferous and other crop plants are reduced considerably when they are grown with other plant species. The aim of a recent project at University of Warwick was to use companion plants instead of insecticides for controlling the cabbage root fly in cauliflower crops. This paper describes some initial experiments to determine how the height, leaf area, leaf shape, proximity and spatial arrangement of companion plants affects host plant selection and oviposition by female cabbage root flies on cauliflower plants. Artificial companion plants were used in the experiments, so that the effects of companion plant architecture could be evaluated critically. The results indicated that to be most effective, the companion plants should be in close proximity to the cauliflower plant. There was evidence that the height of the companion plant foliage was important and that plants that were at least half as tall as the cauliflower plant were more effective, indicating that, to be effective, companion plants have to be relatively tall and erect at the time when the cauliflower plant is most susceptible to damage by cabbage root fly larvae. The size and shape of the leaves of the companion plants appeared not to be critical, allowing some flexibility in the choice of companion species.


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Green bridges over the winter: consequences for Brassica pests
Eefje den Belder, Janneke Elderson, Jane Landure, Danny Esselink, René Smulders

Abstract: In this study we analysed the population genetic structure of the cabbage aphid, Brevicoryne brassicae (L.) (Homoptera: Aphididae) using nine polymorphic microsatellites we have developed. The aim was to determine if the aphid populations are different in genetic structure in relation to the host plant species. Seventeen locations with cruciferous crops/species were sampled during the growing season in the polder Hoeksche Waard (province South Holland), an area covering approximately 400 ha with a high proportion of arable crops including Brussels sprouts and Savoy cabbage, with winter oilseed rape recently introduced and white mustard (Sinapis alba) as the dominant green manure, and several cruciferous crops in a wildlife mixture. Statistical analysis of the genetic structure at the level of the cabbage aphid subpopulations showed no differentiations among the various hosts. Pairwise comparison of the FST values for the aphid samples indicated no significant differentiation between the samples from hosts Brussels sprouts or winter rape in the field margin, sampled in March; oilseed rape and winter rape in the field margin, sampled in May; and Brussels sprouts and winter rape sampled in December. We conclude that green manure crops, field margins with wildlife mixtures containing cruciferous species, but especially oilseed rape can form ‘bridges’ during certain periods of the growing season for infestation of Brussels sprouts by cabbage aphids. In other words: during the period of absence of Brussels sprouts other cruciferous crops or cruciferous plants in margins can harbour populations of cabbage aphids that can infest Brussels sprouts. They function as a ‘seasonal bridge’ for infestation of Brussels sprouts.


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Investigations on root fly control in Germany in 2010
Martin Hommes, Malaika Herbst

Abstract: Several experiments on the control of root flies were conducted in 2010 on JKI field stations at Braunschweig and Berlin. White radish and Chinese cabbage were used as test crops for the control of cabbage root fly [Delia radicum (L.)] and carrots for carrot fly [Psila rosae (Fabricius)], respectively. As a chemical control against adults, spray applications in short intervals during flight activity were tested. The products contained acetamiprid (Mospilan® SG), chlorpyrifos (Gigant® 480 SC), rynaxypyr (Coragen®), cyazypyrTM (DPX-HGW86), spinosad (SpinTor®), or thiamethoxam (Actara®) as active ingredients. The spray treatments were partly combined with a drench of the same product at the beginning of the cropping period. The effect of seed-coating with chlorfenvinphos (Birlane Fluid®), chlorpyrifos (Gigant® 480 SC) or clothianidin plus imidacloprid (Sepresto®) on root fly attack was also investigated,. Furthermore, in 2010 two types of vertical fences, one of which was impregnated with deltamethrin, were tested to prevent root flies from invading the crop. As a biological control agent, field releases of the predator Atheta coriaria (Kraatz) were investigated.


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Supervised control of aphids and caterpillars on white cabbage and impact of flower strips
Martin Hommes, Malaika Herbst

Abstract: In 2008 and 2009 various selective insecticides were investigated for efficacy against different caterpillar species [mainly Mamestra brassicae (L.), Pieris rapae (L.) and Plutella xylostella (L.)] and the cabbage aphid [Brevicoryne brassicae (L.)]. Furthermore, the side effects of the applied insecticides against beneficials as well as the impact of a flower strip on one side of the experimental field on pests and natural enemies were evaluated. For controlling caterpillars, insecticides with the active ingredients Bacillus thuringiensis ssp. aizawai (XenTari®
1 kg/ha), metaflumizone (Alverde® 250 ml/ha), chlorantraniliprole / rynaxypyr (Coragen® 200 ml/ha), indoxacarb (Steward® 85 g/ha) and spinosad (SpinTor® 200 ml/ha) were applied. Plants were treated with the active ingredients flonicamid (Teppeki® 160 g/ha), pirimicarb (Pirimor® 250 g/ha), pymetrozin (Plenum® 50 WG 400 g/ha) and spirotetramat (Movento® 480 ml/ha) against the cabbage aphid. The pesticides were applied in a fortnightly interval after the corresponding action threshold for caterpillars and aphids was exceeded. During one cultivation period, on average 3 to 5 insecticide applications were necessary to control caterpillars and 2 to 3 applications against aphids.


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The biology and control of the currant lettuce aphid Nasonovia ribisnigri
Gemma Hough, Rosemary Collier

Abstract: Nasonovia ribisnigri is the most economically important pest aphid of lettuce. Unlike other lettuce aphids, its preference to feed in the centre of lettuce heads, where it is protected from the effects of certain insecticides and natural enemies, makes it challenging to control. In lettuce IPM programmes, insecticides and resistant lettuce cultivars are recommended to manage this pest. While some systemic insecticides are particularly effective, N. ribisnigri can express resistance to certain insecticides. Lettuce cultivars with resistance to N. ribisnigri (Nr gene) are widely cultivated, but new strains of N. ribisnigri, which can overcome this host-plant resistance, threaten their future.
The aim of this study was to determine whether varying Nr gene introgression backgrounds used by different plant breeding companies have an impact on the level of resistance in their cultivars to UK wild-type and resistance-breaking aphid biotypes. The study screened six Butterheard cultivars including two susceptible cultivars (Clarion and Charles) and four resistant cultivars (Aljeva, Malfalda, Skyphos, Rotary).
The mean percentage of aphids surviving nine days after infestation of the plants with new-born nymphs was determined. Rb N. ribisnigri had relatively high survival on all the Butterhead cultivars, indicating that Rb N. ribisnigri can survive on both resistant and susceptible lettuce cultivars. When comparing the effectiveness of the resistant cultivars in controlling WT N. ribisnigri, there were no significant differences between the cultivars with all aphids suffering almost 100% mortality by day nine. Therefore, these results suggest that the varying Nr gene introgression backgrounds used by different plant breeding companies have no impact on the level of resistance in the cultivar.


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Greenhouse testing of oil products against carrot psyllid (Trioza apicalis)
Anne Nissinen, Lauri Jauhiainen

Abstract: Oil products, Sun 7E or Carbon Kick® Booster, were sprayed on carrot seedlings at the one-leaf stage in concentration of 1.5% to test their efficacy against carrot psyllid adult and nymphal feeding. The first spray was done before releasing one female psyllid per each seedling. Adult psyllids were removed manually after a three-day exposure period. Plants were sprayed a second time when the nymphs were hatched. The spray with oil products did not increase adult mortality. Booster, however, significantly reduced the number of eggs laid per seedling and the number of nymphs per leaf compared to water treatment. Oil treatments, however, did not have significant effect on carrot yield. Booster treatment slightly increased the root weight in control plants, but reduced the root weight in psyllid-exposed plants more than in the other treatments. Triacontanol, added to rapeseed oil in Booster, together with carrot psyllid damage may change photosynthate allocation between the plant organs. Therefore, rapeseed oil products should be tested against carrot psyllid without additional triacontanol.


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First results on population dynamics and chemical control of Aleyrodes proletella in Germany
Ellen Richter, Gunnar Hirthe

Abstract: The cabbage whitefly Aleyrodes proletella is a well known pest of vegetable brassica species. Since more than a decade, it is a constant and relevant pest in Germany with mass reproduction in several cabbage species. Damages occur particularly on Brussels sprouts, kale, kohlrabi, and savoy. Produce quality is affected by the sole presence of the insects; furthermore, the produce is contaminated by honeydew and sooty mould fungi.
Until now, there is only little information available on the population dynamics of A. proletella. It seems that the enormous reproductive potential is a result of at least four generations, with the first generation developing on overwintering brassica species. In northern Germany oilseed rape offers an exclusive hibernation habitat for the cabbage whitefly. With the ripening of the rapeseed plants in May/June, the young adults leave the crop searching for new host pants. After invading Brussels sprout in June, a mass reproduction of whiteflies with up to 60,000 larvae per plant until to September could be observed in 2010.
From 2008 to 2009 studies were undertaken to test two different methods of chemical control with different insecticides. The first step was to drench seedlings of Brussels sprouts with systemic insecticides before transplantation. The second step was to test field spray applications. Best insecticides for drench application were imidacloprid and thiamethoxam. For spray application flonicamid and spirotetramat revealed best efficacy. Adding rapeseed oil or a wetting agent improved efficacy of some insecticides.


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Importance of biotype Nr:1 of the currant lettuce aphid Nasonovia ribisnigri (Mosley) in north and central Switzerland
Cornelia Sauer-Kesper, Noël Lucia, Ute Vogler

Abstract: The currant lettuce aphid, Nasonovia ribisnigri (Mosley) is the most common aphid species on field-grown lettuce in Europe. Cultivation of lettuce varieties, resistant to the currant lettuce aphid (conferring the resistance Nr:0), was an important tool to control the infestation with N. ribisnigri in the crop, until plant resistance was broken.
In 2007, a new biotype of the currant lettuce aphid was observed, which overcomes the lettuce resistance Nr:0. This biotype of N. ribisnigri is designated as biotype Nr:1. Its presence was recorded in north and central Switzerland for the first time in 2008. The dispersion of biotype Nr:1 in these parts of Switzerland was monitored using field collected aphid samples for biotests in a climate chamber. According to the results, biotype Nr:1 colonized the main lettuce production areas and also dispersed to remote sites by 2010.
In comparison to susceptible lettuce, the biotype Nr:1 had lowered performance on Nr:0 resistant lettuce cultivars. Therefore, lettuce varieties conferring the Nr:0 resistance are useful to reduce the infestation by the biotype Nr:1. Although the resistance is broken, their cultivation is still recommended.


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VIPS – warning and prognoses of pests and diseases in Norway
Annette Folkedal Schjøll, Guro Brodal, Richard Meadow & Halvard Hole

Abstract: VIPS (Varsling Innen PlanteSkadegjørere) is a web-based decision support system designed to assist Norwegian growers in the management of pests, diseases and weeds of cereals, vegetables and fruit crops. VIPS was established in 2001 as a collaborative project between Bioforsk and Norwegian Agricultural Extension Service (NAES) under a government-funded action for reducing risk connected to the use of pesticides. The aim of VIPS is to provide information to advisors and farmers to reduce reliance on pesticides.
Inputs to the forecasting models are weather data from the Bioforsk Agrometeorological Service consisting of a network of more than 80 automatic weather stations across crop production areas, weather forecasts from the Norwegian Meteorological Institute and biological/field observations collected by NAES. A general interface is used for all models incorporated in the system, allowing new models to be easily implemented. During the growing season the monitoring of several pests and diseases are recorded through a message system in VIPS. Included in VIPS is also a programme to assess the need for control of weeds in cereal fields (choice of herbicide(s) and calculation of doses). The service is open and free of charge at Warnings are also available as sms messages.
Current development aims at transferring the service from weatherstation-based to farm-based pest forecasts. Use of radar measurements of precipitation in combination with interpolation of the other weather factors from the nearest weather stations is expected to improve precision in the pest forecasts as well as farmers “ownership” of the information presented.


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Pea odorants guide host finding behaviour in pea moth: a new strategy for insect management?
Gunda Thöming, Helmut Saucke, Geir K. Knudsen

Abstract: The pea moth Cydia nigricana (Lepidoptera: Tortricidae) is a major pest in pea growing areas. Alternative pest control techniques are needed since efficient control options are scarce. A strong correlation between the seasonal flight period of C. nigricana and the phenology of the pea plant Pisum sativum (Fabaceae) has been shown in field studies in Northern Hesse, Germany, in the years 2006-2008. In our current studies we are investigating the olfactory space between the pea moth and pea plant, aimed at the identification of volatile cues encoding host recognition and host finding in pea moth females, and the use of these volatile compounds for management of the pea moth. In dual-choice experiments in insect cages, the preference between potted pea plants of different phenological development stages was tested, using male and female C. nigricana (mated and non-mated). Mated females clearly prefer flowering pea plants, whereas non-mated females and males showed no preference. In wind tunnel experiments the upwind orientation of C. nigricana towards the odour of pea plants of different phenological development stages was tested, using pea plants (A) and headspace collections of pea plants (B) as the odour source. In both wind tunnel set ups (A and B), the preference of mated females for the pea flower has been confirmed and additionally, strong attraction of mated females for the late bud stage was recorded. Overall, the flower and the late bud stage of P. sativum seem to be the most important phenological development stages for the host finding behaviour of C. nigricana. In ongoing studies we are identifying and characterising the behavioural active volatile compounds of the pea plant, using GC-MS (coupled gas chromatography – mass spectrometry) and GC-EAD (coupled gas chromatography – electroantennographic detection).


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New protection strategies for the carrot fly (Psila rosae Fab., Diptera, Psilidae) in France
François Villeneuve, François Latour

Abstract: The carrot fly (Psila rosae Fab.) is a major pest of carrot crops in France and throughout Northern Europe. There can be three generations per year in the climatic conditions of France. This pest is taking on new importance with the reduction in the number of active ingredients now available for crop protection due to the withdrawal of organophosphates and carbamates: currently, only pyrethrins are available. Hence the need to initiate research into new means of both chemical and alternative control.
In the first stage of the trials, encouraging results were obtained with several new active ingredients. However, it is necessary to initiate new protection strategies, based on various methods of supervised control and various active ingredients.


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Possibilities of risk forecasting for the carrot fly (Psila rosae Fab., Diptera, Psilidae) in the south of France
François Villeneuve, François Latour

Abstract: In France, as in northern Europe, the carrot fly is an important pest of Apiaceae cultures (carrots, celeriac, parsnips...). This pest takes on a new importance with the reduction of active ingredients available to growers for crop protection.
Research is being conducted on risk forecasting models, in particular the German model SWAT. Unfortunately, SWAT does not yet allow a suitable forecast of the risks under the conditions of southwest France: first flight predicted too early and flight predicted for June-July not observed; overwintering in the form of larvae and not in the form of pupae in the more northern zones. Lastly, with the strong thermal amplitudes observed, it is necessary to take into account the values of maximum temperatures after the first flight for the evaluation of the second flight, which occurs in autumn.


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Towards a push-pull-kill strategy for the cabbage and turnip root flies in broccoli using Chinese cabbage, red clover and Entomophthora muscae
Maria Björkman, Annette Folkedal Schjøll, Pierre Antoine Allard, Idun Bratberg, Richard Meadow, Ingeborg Klingen

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Impact of landscape on cabbage pests and natural enemies: Launching a system oriented plant protection approach
Martin Ludwig, Rainer Meyhöfer

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IPM in cabbage crops – first results of cabbage root fly control in the EU-project “PURE” in Germany
Malaika Herbst, Martin Hommes

Abstract: In 2012 the impact of different plant protection products on the cabbage root fly (Delia radicum (L.)) were investigated concerning their efficacy. Cauliflower plants were treated with spinosad (SpinTor® 12 ml/1000 plants), entomopathogenic nematodes (Steinernema feltiae 180.000 nematodes/plant in 50 ml H2O), lime nitrogen (PERLKA® 4.5-5 dt/ha) and the entomopathogenic fungi Beauveria bassiana (Bals.-Criv.) Vuill. (Naturalis® 1 ml/plant in 50 ml H2O/plant). At harvest the number of pupae and larvae in the soil around roots was assessed and the root damage quantified. Furthermore the impact on the head weight was regarded. Among the different plant protection products tested, only spinosad showed pupae and larvae reducing properties and a slight trend towards lower root damage. However no influences of the different treatments on the mean head weight were found.


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Digital monitoring methods for cabbage pests
Nelli Rempe-Vespermann, Martin Hommes, Daniel Mentrup, Arno Ruckelshausen

Abstract: In order to be able to apply insecticides selectively, thresholds as well as current infestation probability must be known. The probability of infestation of certain pest can be determined by different estimation methods. The available monitoring methods for pests in vegetable crops under field condition are time-consuming, labor-intensive or not field-specific. Automation can simplify monitoring. In 2013, the first automatic systems were tested under field conditions. The digital detection of pests was possible with three systems: TrapView, a modified funnel trap and a TriangelCameraSystem. In particular, TrapView and TriangelCameraSystem turned out to be most promising.


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Biology of the cabbage whitefly, Aleyrodes proletella
Spencer Collins

Abstract: Historically the cabbage whitefly (Aleyrodes proletella) has been a minor pest of Brassica crops (Butler, 1938a), but recently it has become an increasing pest in Europe particularly of Brussels sprout and kale (Nebreda et al., 2005). The cause of this is not fully understood, but is believed to be due to a combination of factors. Knowledge about the biology of the cabbage whitefly is limited and most of what is currently understood about its ecology has been inferred from minimal anecdotal evidence. The overall aim of this project is to understand population trends of Aleyrodes proletella in the most vulnerable crops, Brussels sprout and kale. This includes understanding the key times of population/generation increase and colonisation of a new crop. This information can then be used to inform the development of an integrated control strategy using insecticides and other tools, which might include biological control agents and methods of cultural or physical control. Field populations of whitefly were surveyed on newly planted Brussels sprout and kale crops. Colonisation of the crop occurred before the emergence of the first generation adults on overwintering plants suggesting that overwintering females were the first to colonise, a fact that was not believed to be the case. Sampling will continue until early 2014. A commercial crop of oilseed rape was not found to support overwintering whitefly however this may have been caused by excessive damage by pigeons. Further surveys will be conducted in specialist areas of Brassica cultivation as these regions may support larger populations of whitefly.


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Hibernation and migration of Aleyrodes proletella in Germany
Ellen Richter, Gunnar Hirthe

Abstract: The cabbage whitefly Aleyrodes proletella is a well known pest of vegetable brassica species. Since more than a decade, it is a constant and relevant pest in Germany with mass reproduction particularly on Brussels sprouts, kale, kohlrabi, and savoy. Produce quality is affected by the presence of the insects; furthermore, the produce is contaminated with honeydew and sooty mould fungi.
The reasons for this increasing relevance are not clear and until now, there is only little information available on the population dynamics of A. proletella. First questions are related to the hibernation habitat and the migration behaviour. In northern Germany oilseed rape offers an exclusive hibernation habitat for the cabbage whitefly. With the ripening of the rapeseed plants in May/June, young adults leave the crop searching for new host pants. In the warmer western and south-western vegetable production areas rapeseed is not available. In these areas overwintering cabbage crops represent the most suited hibernation host. Invading of spring planted cabbage crops takes place from May to July. Depending on the weather conditions in spring and summer and the availability of hibernation hosts, A. proletella is capable of mass reproduction with up to 60,000 larvae per plant, which was found in Brussels sprouts in September 2010.


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Efficacy of drench and spray applications of insecticides to control cabbage whitefly Aleyrodes proletella
Ellen Richter, Gunnar Hirthe

Abstract: For several years, the cabbage whitefly Aleyrodes proletella Linnaeus has been an important pest affecting the production of Brussels sprouts, kale, savoy and kohlrabi in Germany. From 2008 to 2009 studies were undertaken to test two different methods of chemical control with different insecticides. The first method was to drench seedlings of Brussels sprouts with systemic insecticides before transplanting. The insecticides included were acetamiprid, clothianidin, dimethoate, emamectin, flonicamide, imidacloprid, pymetrozine, spirotetramat, and thiamethoxam. The most efficient insecticides for drench application were the neonicotinoids imidacloprid and thiamethoxam, resulting in a remarkable efficacy even 16 weeks after treatment. The second method was to test field spray applications. The insecticides included were acetamiprid (sole and in combination with rapeseed oil or a wetting agent), azadirachtin A, bifenthrin, chlorpyrifos-methyl, clothianidin, emamectin, flonicamid plus methylated oil, pymetrozine plus methylated oil, potassium soap, plant oil, pyrethrine plus oil, and spirotetramat. For spray application spirotetramat showed the best efficacy. Adding oil or a wetting agent improved efficacy, e.g. for acetamiprid and flonicamid.


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The role of naturally occurring insect pathogenic fungi in regulating aphid populations on vegetable Brassica crops
Liam Harvey

Abstract: Aphids are important pests of crop plants, and are a particular problem on the 26,000 ha of vegetable Brassica crops grown annually in the UK. They cause direct feeding damage and are vectors of plant pathogenic viruses. At present, aphid control is heavily reliant on chemical insecticides but growers are under pressure to reduce insecticide usage. Aphid populations increase in the spring and autumn months interspersed with a period during midsummer when they decline rapidly. At present, the timing of this mid-season population ‘crash’ cannot be predicted accurately. If a forecast was developed growers could be alerted of when a crash was likely, which would give them the option to withhold insecticide applications. Natural enemies, and in particular entomopathogenic fungi, have been implicated in the crash, but little is known of their biology. The aim of this project is to quantify the effects of the associated guild of natural enemies of aphid populations in field brassicas.


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Impact of oilseed rape on initial colonisation and pre-harvest infestation of Brussels sprouts
by cabbage aphid, cabbage whitefly and whitefly parasitoids

Martin Ludwig, Hella Schlinkert, Rainer Meyhöfer

Abstract: Most crops are annually recolonised by insect pests from source and overwintering habitats. Detailed knowledge on these source habitats is of vital interest for plant protection. This knowledge can be used for risk assessment of crop fields and for development of pest prevention strategies. Here we evaluate the relevance of oil seed rape farming for colonisation and infestation of cabbage by phloem sucking pests and their natural enemies. We were in particular interested in initial colonisation in July and infestation shortly before harvest in October. Nineteen farms growing organic Brussels sprouts in landscapes with different amounts of oil seed rape were selected. The colonisation process and infestation by pests and natural enemies on Brussels sprouts was monitored from June to November. Results showed that cabbage whitefly (Aleyrodes proletella) and cabbage aphid (Brevicoryne brassicae) were the main pest species in the region. The peak of colonisation was in June for both species, while highest whitefly infestations were reached in October. The abundance of cabbage whiteflies on monitoring plants increased with oilseed rape growing, while no effect on cabbage aphids and whitefly parasitoids could be detected. Generally, an increase in oilseed rape growing offers additional overwintering and reproduction sites for cabbage pests and therefore is supposed to benefit the colonisation on cabbage. We found evidence that oilseed rape growing increased colonisation and peak infestation by cabbage whiteflies. So far no significant effects on cabbage aphid and whitefly parasitoids could be detected. For aphids this may be explained by higher susceptibility of aphids compared to whiteflies to insecticide spraying in oilseed rape. The investigations are being continued taking into account larger landscape areas, temperature and wind data.


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Trap crops as a pest management strategy for carrot psyllid (Trioza apicalis)
Ulf Nilsson, Birgitta Rämert

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Leaf miner in leek (Phytomyza gymnostma) – a rising concern?
Martin Hommes, Andreas Willhauck

Abstract: Between 2009 and 2012 several experiments with different insecticides to control the onion thrips [Thrips tabaci (Lindeman, 1889)] were conducted on JKI field stations. Within these experiments a direct control of the allium leaf miner [Phytomyza gymnostoma (Loew, 1858)] did not take place between 2009 and 2011 but side effects of the thrips control against the allium leaf miner were observed. From the year 2012 the allium leaf miner was included in the control strategy. The trials were carried out on an organic and a conventional experimental field. As test crop leek was used. The insecticides were tested as spray application against adult flies in different intervals during the flight period. The active ingredients and products used in the experiments on the organic experimental site were a combination of pyrethrine and rape oil (Spruzit Neu®), potassium salts (Neudosan Neu®), spinosad (SpinTor®), rape oil (Micula), azadirachtin (NeemAzal®) and on the conventional experimental site spinosad (SpinTor®), spirotetramat (Movento®), abamectin (Vertimec®), lambda-cyhalothrin (KarateZeon®), chlorpyrifos (Dursban 20 SC®), cyantraniliprole (Cyazypyr™) and a combination of thiacloprid and deltamethrin (Proteus®). Additionally, the products Vertimec®, KarateZeon® and SpinTor® were combined in a resistance strategy.


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Alternative use of a decision support model to control thrips in leek
Hilfred Huiting & Gijs van Kruistum

Abstract: Onion thrips (Thrips tabaci Lind.) is considered the most important insect pest of leek crops in Southern and Western Europe. Damage consists of silvery mottling – sometimes in longitudinal stripes – resulting from air filled plant cells after puncturing and sucking the sap by thrips. Damage is predominantly cosmetical but high population pressure may additionally hinder plant development, especially at early development stages or in stressful circumstances. Given the high reproduction rates and high mobility of the polyphagous onion thrips, combined with the year round leek cultivation in the Netherlands, population pressure is always considerable, as winter shelters are abundant. In this situation much attention is given to adequate thrips control, mainly based on regular insecticide sprays. Since leek crops are mostly transplanted in the Netherlands instead of direct sown, the crop protection effect of a possible insecticide seed treatment is limited in the field.
In the past spray schedules relied heavily on contact insecticides and/or based on the systemic insecticide methiocarb. However limitations both in the number of registered insecticides and in the number of applications per crop have shifted the focus towards alternative thrips control strategies. The growers' struggle to optimise the use of the three registered active ingredients – deltamethrin, abamectin and spinsosad – within the label restrictions, has led to practical experiments with the Dacom Thrips Prediction Model, a decision support system (DSS). This temperature based thrips prediction model forecasts the occurrence of thrips based on the threshold development temperature and the actual temperature, indicating the optimal spraying moment. Growers are fairly satisfied with the DSS, although one practical drawback appeared to be its inability to anticipate on the onsite thrips population situation.
Based on the DSS a new spray strategy was tested in three consecutive field trials in 2009-2011. In a crop planted in early June, thrips control was postponed until the second half of August. Subsequently three or four spray applications alternating spinosad and abamectin at 7-10 day intervals sufficed to control leek damage resulting in the same product quality as with the practical 9-11 spray passes strategy. The tested strategy may open new possibilities to integrated pest management, lowering the total insecticide input and giving more room to non-chemical control options.


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Mites in the witloof chicory production: Occurrence, identification and pest management strategies
Ute Vogler, Margareta Scheidiger, Christian Linder, Serge Fischer

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A host-pathogen-parasitoid system in the biological control of the cabbage root fly, Delia radicum
Belén Cotes, Linda-Marie Rännbäck, Peter Anderson, Nicolai Vitt Meyling, Maria Björkman, Birgitta Rämert

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Feeding of turnip root fly (Delia floralis) and cabbage root fly (Delia radicum) larvae
on Brassica napus L. transgenic MINELESS plants – Effects on insect development

Maria Björkman, Ishita Ahuja, Annette Folkedal Schjøll, Nicole Marie van Dam, Atle Magnar Bones, Richard Meadow

Abstract: The dual component glucosinolate-myrosinase defence system is present in plants of the Brassicaceae. Upon insect attack, the defence system gets activated and forms glucosinolate hydrolysis products, which affect insect herbivory. The transgenic Brassica napus MINELESS plants have been produced by genetic ablation of myrosin cells, cells containing the myrosinase enzymes acting in the mustard bombs or toxic mines. In this study we analysed how the larvae of Delia radicum and D. floralis perform on wild-type and MINELESS B. napus plants and how these plants are affected. The larvae of both D. radicum and D. floralis gained more weight after feeding on MINELESS roots. Both aboveground and belowground plant biomass were observed to be higher for MINELESS plants compared to the wild-type on day 4 regardless of attack by D. radicum and D. floralis. We conclude that ablation of myrosin cells had a slight but not dramatic effect on the feeding behaviour for D. radicum and D. floralis.


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The cabbage root fly Delia radicum (Diptera: Anthomyiidae) and downy mildew Peronospora parasitica (Oomycete: Peronosporales) in the vegetable brassica-oilseed rape agroecosystem
Ute Vogler, Romana Schmon, Melanie Jänsch, Werner Heller

Abstract: Cruciferous plants (Brassicaceae) represent economically important crops for Swiss agriculture, comprising i.e. vegetable brassica and oilseed rape (Brassica napus L. emend. Metzg.). However, cultivation techniques of the crops differ, for example in terms of plant protection measures. To prevent economic losses in the production of vegetable brassica, measures to protect plants from infestation with the cabbage root fly Delia radicum (Diptera: Anthomyiidae) have to be applied and infection with downy mildew Hyaloperonospora (= Peronospora) parasitica (Oomycete: Peronosporales) must be prevented. In contrast to vegetable brassica production, D. radicum and P. parasitica are not known to cause significant economic losses in oilseed rape production in Switzerland.
To determine the importance of oilseed rape as source of pest and pathogen inoculum within the vegetable brassica-oilseed rape agroecosystem, we monitored the abundance of D. radicum and analysed plants for H. parasitica infection.
The abundance of D. radicum was monitored in 2012 in a field with vegetable brassica, i.e. cauliflower (Brassica oleracea var. botrytis L.), and in three fields with oilseed rape in the region of Lucerne, Switzerland. For monitoring, we used one yellow water trap per field. The distance between the traps ranged from 330 m to 1400 m. Captured flies were identified and sexed in the laboratory. Additionally, oviposition of D. radicum was checked weekly at ten randomly selected plants per field. Monitoring revealed that the time of emergence of D. radicum is not influenced by the presence of host plants. However, our results showed that overwintering site and host plant availability influenced the initial population size of D. radicum in spring.
Seedlings of vegetable brassica with visible H. parasitica symptoms, and seeds and seedlings of oilseed rape with or without visible symptoms of H. parasitica were analysed with molecular techniques. The results of the investigations revealed that vegetable brassica seedlings, seeds and seedlings of oilseed rape were infested with H. parasitica. Furthermore, the results of the molecular analyses showed that all collected samples of H. parasitica from vegetable brassica and from oilseed rape belong to the same population.
In conclusion, with an increase in the oilseed rape production area in Switzerland, undisturbed overwintering sites and infestation levels of D. radicum are increasing in vegetable brassica and in oilseed rape cultures. Additionally, the distribution and epidemiology of H. parasitica in vegetable brassica and in oilseed rape is enhanced by the increasing oilseed rape production area in Switzerland as well.


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Interactions between two brassica specialists in a trap crop system –
effects of Plutella xylostella larval feeding on Delia floralis host plant choice

Maria Björkman, Annette Folkedal Schjøll, Brooke Peterschmidt, Richard Meadow

Abstract only


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From Agrotis segetum pheromone trap catch to subsequent injury?
Peter Esbjerg

Abstract only


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