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IOBC-WPRS Bulletin Vol. 64, 2011

 

IOBC-WPRS Bulletin Vol. 64, 2011

Working Group "Insect pathogens and entomopathogenic nematodes, Subgroup Slugs and Snails".
Proceedings of the meetings at the Inforama Rütti - Zollikofen, Bern (Switzerland), 2 - 4 April, 2007 and at Cardiff University (Wales, UK), 23 - 25 March 2010.
Edited by: Solveig Haukeland, Bill Symondson, R. Andrew King, Emma M. Shaw and James R. Bell.
ISBN 978-92-9067-239-5 [XII + 240 pp.]

 

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The slug Arion lusitanicus Mabille in Norway. 1. Testing control methods
in private gardens

Arild Andersen

Abstract: Different methods to reduce the population of Arion lusitanicus are being tested in
private gardens already infested naturally with the slug, as well as and in arenas in the laboratory.
After the first 2 years out of a 4 year project the following preliminary trends has been observed:
Untreated gardens had the highest populations. Gardens with owners trapping and killing slugs
had the lowest populations. Gardens that were rearranged to become drier had intermediate
populations. In arenas in the laboratory, slugs avoided cocoa chips mulch and alginate.

1-2

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Slug control in no-till agriculture and slug population monitoring
Markus Bieri, Evelyne Joliat, Andreas Chervet & Wolfgang G. Sturny

Abstract: In the long-term field trial “Oberacker” of the Soil Protection Service, the slug
populations were monitored and the effects of slug control treatments with Metaldehyde slug
pellets were investigated. It was found that in the “no-till” plots the slug population recovers very
fast and reaches within a summer the same level as in spring. In “no-till” agro ecosystems the
slug populations are constantly on a high level and have to be monitored all year round to
undertake slug control measures at the right time.

3-8

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Can scavenging suppress application success of pathogenic nematodes?
Pavel Foltan & Vladimir Puza

Abstract: Two-choice trials were used to assess prey choice of the generalist predator/ scavenger
Pterostichus melanarius (Coleoptera: Carabidae) between Deroceras reticulatum (Mollusca:
Agriolimacidae) slugs or wax moth Galleria mellonella (Lepidoptera: Pyralidae) larvae killed by
infection of P. hermaphrodita /Steinernema affine and control killed by freezing. We demonstrate
that the presence of either of the two nematodes tested deters the beetles from consuming
infected cadavers. This mechanism enables the nematodes to survive extreme scavenging
pressure during their development inside cadavers.

9-12

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Efficacy of pesticide seed treatment of oilseed rape to control slug damage
Hilferd F. Huiting & Albert Ester

Abstract: Slugs are an important pest of oilseed rape. The most susceptible plant stages are from
the start of germination until the second leaf has been formed. Damage results in open spots in
the field which can cause yield loss, weed problems and variation in ripening. Baited
molluscicide pellets are predominantly used to control slugs often resulting in inadequate control.
One laboratory experiment and two field experiments were carried out to test the efficacy of filmcoating
oilseed rape seeds to protect the crop against slug damage. Treatments were compared
with an untreated control as well as a reference treatment in the field experiments consisting of
broadcast applications of metaldehyde slug pellets at a rate of 448g a.i./hectare. In conclusion,
metaldehyde showed sufficient protection of the crop against slug damage at rates from 80g
a.i./kg seed upwards and thiacloprid protected the oilseed rape from rates of 38.4g a.i./kg seed
upwards. Results of imidacloprid were variable showing good protection in 2006/2007 only. The
remaining pesticides failed to protect the oilseed rape. Results are discussed with particular focus
on the variation in results between metaldehyde and imidacloprid and thiacloprid.

13-22

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Recent advances in the taxonomy of the NW European slugs of the genus Arion
(Mollusca, Gastropoda, Pulmonata)

Kurt Jordaens, Anton de Winter, Karin Breugelmans, Jan Pinceel, Sofie Geenen, Hilde Vrijders & Thierry Backeljau

Abstract: Many NW European slug species are serious pests in agriculture and horticulture. A
sound knowledge of the slug’s life cycle is essential in order to successfully control slug
numbers. However, for many slug species, knowledge of their biology is scarce and insufficient
because they prove difficult to identify. Many slugs are now considered complexes of sibling
species whereas several species also show a high intraspecific variation in external and genital
morphology. Here, we provide an overview on the current knowledge on the morphological,
anatomical and molecular characterisation of the NW European species of the land slug genus
Arion (family Arionidae).

23-39

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Biodiversity of terrestrial molluscs in urbophytocoenoses of Vilnius,
capital of Lithuania

Viktorija Kuznecova & Grita Skujienė

Abstract: A total of 6941 terrestrial molluscs of 50 species, belonging to 16 families were found
during 2006 May-October in three urbophytocoenoses of parks of Vilnius and 27 species of 12
families are known as the most important pest Gastropods according to D. Godan (1983). Two
species were new for the Lithuanian fauna – Oxychilus draparnaudi (Beck, 1837) and Oxychilus
alliarius (Miller, 1822) – and these species are known in Europe as pest Gastropods, too. The
most abundant (eudominant) species were: Vallonia costata (O. F. Müller, 1774), Succinea putris
(Linnaeus, 1758), Vitrina pellucida (O. F. Müller, 1774), Nesovitrea hammonis (Ström, 1765),
Xerolenta obvia (Menke, 1828), Trichia hispida (Linnaeus, 1758), Arianta arbustorum
(Linnaeus, 1758), Laciniaria plicata (Draparnaud, 1801). Diversity of molluscs in parks of the
biggest city of Lithuania is the same as the number of species in Natural National park in Latvia –
50-51 species. Ability of Clausiliidae (8 species), Vertiginidae (6 sp.) and Pupillidae (1 sp.)
shows that environment conditions are quite tolerable for the diversity of land molluscs community.

41-51

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Spatial distribution and activity of Microxeromagna armillata
in an Australian citrus orchard – implications for pest management

Angela Lush, Michael Keller, and Geoff Baker

Abstract: Microxeromagna armillata is a small, cryptic, introduced snail which inhabits both
terrestrial and arboreal environments in Australian citrus orchards. This species has caused
significant problems for the citrus industry as a contaminant on exported produce to the United
States of America. Snails have been found sheltering in the navel of export oranges, and costly
quarantine measures have been established when interceptions occur on produce. As the USA is a
key export market for Australian Navel oranges, M. armillata poses a serious problem for the
industry. A key factor impeding development of a targeted control strategy is the lack of
understanding of M. armillata’s spatial distribution and activity in the tree canopy.
In this paper, the activity patterns of M. armillata during fruit harvest and post harvest are
reported. Microxeromagna armillata was active in all areas sampled within the orchard, although
snails were not equally active in all areas or on all sampling dates. Snail activity levels decreased
with increasing height above ground during both the harvest and post harvest periods, with
activity on all surfaces higher during the latter.
These findings suggest that late harvested citrus varieties may be more susceptible to
contamination by M. armillata, reinforce the recommendation to skirt trees, and highlight the
need to keep fruit-picking bins off the orchard floor.

53-57

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Manipulation of slug spatial behaviour by the rhabditid nematode
Phasmarhabditis hermaphrodita

Hana Pechova & Pavel Foltan

Abstract: Post-mortem location of slugs killed by six different treatments (three types of
molluscicides, simulation of unsuccessful predation and two P. hermaphrodita nematode
treatments) were compared. In comparison to other pathogenic states, significantly more slugs
killed by the nematodes died within the soil. We assume that this is an outcome of behavioural
manipulation, which prevents the parasites from being predated or scavenged together with their
host until the nematodes complete development inside the host cadaver.

59-62

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Impact of molluscicidal formulations of earthworm surfacing behaviour:
a novel use of security cameras

Emma M. Shaw & A. Mark Langan

Abstract: Earthworms are of paramount importance in many soil systems, often comprising the
dominant fraction of the soil macrofauna. Their activities have positive influences on soil
functioning, recycling nutrients and promoting plant root growth for example. Pelleted
methiocarb and, more recently iron phosphate, molluscicides can impact on earthworm
populations. The Daniel funnel test was used to determine the impacts of an iron phosphate and
metaldehyde molluscicide on nocturnal surfacing behaviour and feeding of Lumbricus terrestris.
This technique monitors the removal of pellets and food (leaf portions) from the soil surface, but
lacks detailed information regarding the level of direct interaction between pellets and
earthworms. Therefore, night vision security cameras were mounted above a number of burrows
and, with the help of motion detection software, earthworm activity was filmed. This allowed
earthworm surfacing patterns and the frequency and duration of pellet contact to be documented
for the first time. Metaldehyde was found to have no significant impact on earthworm behaviour
whilst iron phosphate significantly reduced surfacing behaviour and feeding frequency.

63-68

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Molecular identification of interaction pathways between carabid beetles and slugs in alfalfa
Mark K. Adams, Eric G. Chapman & James D. Harwood

Abstract: Global trade facilitates the intercontinental movement of cargo and thus increases the
potential introduction of exotic gastropods to new areas of the world. Hence, there is a growing
need to understand ecological interactions of newly introduced species with the native fauna.
Furthermore, exotic slugs are of particular concern because yield losses to commodities planted
throughout much of the continental United States are high and states such as Kentucky, whose
humid climate typically supports a high density of these species, have significant acreage of
farmland planted to crops at risk of damage including alfalfa, soybean, wheat and corn. Given
these concerns, and the high density of endemic natural enemies inhabiting these agroecosystems,
it is essential to examine the mechanisms of predation, decipher the strength of interaction
pathways and evaluate the role of predators in biological control. In 2008, over 1,000 specimens
of three species of ground beetles (Carabidae) were collected from alfalfa and screened by
polymerase chain reaction using species-specific primers to identify the presence of DNA of the
exotic slug Deroceras reticulatum. Feeding trials indicated that slug DNA was detectable in
predator guts for approximately 12 h and, significantly, during the month of June, 5% of
Harpalus pensylvanicus, 25% of Scarites quadriceps and 5% of S. subterraneus specimens
screened positive for D. reticulatum DNA. Drought conditions thereafter likely caused slug
predation rates to decrease as their availability to epigeal predators declined. This research has
enhanced our understanding of complex and emerging slug-carabid interactions in North
America and provides a valuable framework for future efforts in conservation biological control.

71-74

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Natural mollusc repellents and molluscicides based on Somali oleoresins
Ahmed Y. Ali, Catherine J. Whaley, Jon B. Court & Ifor D. Bowen

Abstract: The Somali oleoresins, commonly known as frankincense (Boswellia carteri), myrrh
(Commiphora molmol) and opoponax (Commiphora guidotti), were evaluated for their potential
as natural slug control agents. Split substrate assays were used to compare the effect of various
varnish paint formulations, containing Somali oleoresins and a chemical component, on
Deroceras reticulatum slugs. Paints containing frankincense or a chemical component from
opoponax (CDF1) demonstrated high incidences of slug death or paralysis. In contrast, varnish
paint containing opoponax oleoresin showed no molluscicidal or sub-lethal activity but displayed
significant slug repellence properties. Myrrh, formulated as a topical foliar spray, was applied at
various application rates to a field planted with a crop of pansy flowers. The optimum application
(20ml/L), significantly reduced the feeding activities of Deroceras spp. and Arion spp. slugs. The
spray also significantly reduced plant damage to levels comparable to those observed with
commercial Metaldehyde based pellets. After fourteen days, no signs of phytotoxicity and
negligible levels of slug mortality were observed. This study validates the use of Somali
oleoresins as an alternative means of controlling slugs both in home and garden and field
situations.

75-79

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Reducing numbers or populations of the Iberian slug (Arion lusitanicus)
in private gardens in Norway

Arild Andersen

Abstract: Sixteen gardens in South-eastern Norway were divided into 4 groups of 4 gardens. In
treatment 1 (untreated control) nothing was done to reduce slug numbers. In treatment 2
(‘killing’) the owners were encouraged to collect and kill as many slugs as possible. In treatment
3 (habitat manipulation) owners were encouraged to change their garden so that an area of about
20cm close to the ground was kept as open and dry as possible. Treatment 4 (extended habitat
manipulation) included treatment 3 but also by removing of potential overwintering sites such as
open compost, heap of stones etc. A reduction in the number of slugs was observed in all the
years and in all treatments from June to September, probably due to natural mortality. The mean
number of slugs was always lowest in treatment 2, in the third year showing a significant
reduction of more than 80% from the control. In treatment 4 the mean reduction of slugs (not
significant) was almost 40% during the third year. In treatment 3 the mean reduction (not
significant) was about 55% during the third year. In conclusion, creating a garden not favourable
to the Iberian slug can reduce the population without using molluscicides.

81-83

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The effect of slugs on seedling recruitment and community composition
in upland hay meadow plant communities

Sarah Barlow, Roy Sanderson & Gordon Port

Abstract: Restoration of species-rich upland hay meadows is a target of the EC Habitats
Directive and the UK Biodiversity Action Plan for Upland Hay Meadows. Previous restoration
research has predominantly focused on the optimum farming management regime, and
interactions between the above ground vegetation and the soil microbial community, with little
attention being paid to the role of grazing invertebrates. Slugs have the potential to affect
seedling recruitment and community composition through the selective removal of favoured
species at the seedling stage. A mesocosm experiment was designed to test this hypothesis over a
three year period. Results showed a significant effect of slug grazing on community composition
one year after sowing, with evidence of selective grazing on Rhinanthus minor L. (Hay rattle)
(Orobanchaceae) seedlings. The selective removal of R. minor, a hemi-parasite and keystone
species, by slugs, is of critical interest to the restoration process as R. minor is used as a
management tool to reduce the dominance of competitive grass species in species-poor meadows
that are targeted for restoration.

85-89

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Slug control using Metaldehyde under modern ecotechnological aspects
Rolf Barten & Jaeger, C.

Abstract: For many years Metaldehyde based products have been successfully used for the
control of slugs and snails throughout Europe and beyond. Metaldehyde is particularly suited for
integrated mollusc control programs and has therefore gained widespread usage in arable and
horticultural crop situations. As with any pesticides, the form of delivery of the active ingredient
in the product formulation can become the decisive factor not only for the potential of biological
control but also for any unwanted side effects. For example, recent findings of Metaldehyde
residues in raw water sources in the United Kingdom have raised concerns about the future of
this active substance. Leading bait manufacturer frunol delicia has developed new bait formulas
using a novel manufacturing process allowing to significantly reduce the concentration of
Metaldehyde in the bait formula and the application rate per hectare. Following ten years of field
experience, the eco-balance, in terms of reduction of both the active ingredient consumed and the
carbon dioxide produced, confirms a viable way of how solutions in bait manufacturing can help
to maintain Metaldehyde as an integrative active ingredient for reliable and eco-friendly slug
control even in future years.

91-92

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Observations of field slug activities in Switzerland in relation to weather conditions
Markus Bieri, Florian Burkhalter, Andreas Chervet, Wolfgang G. Sturny & Susanne Appoloni

Abstract: Over the last years the slug activity-density (method: Glen et al., 2003) was monitored
from early spring to midsummer (growing season) in a no-tillage plot and a plot with
conventional plough tillage in the “Oberacker” long-term field trial of the Office of Soil
Protection at the Inforama Ruetti in Zollikofen (Switzerland). In a first evaluation the numbers of
observed animals were compared with the weather conditions over these years. In this study the
parameters of the over-wintering conditions for slugs are investigated. The main factors
influencing the over-wintering populations are also found to be soil temperature and soil matrix
potential. Soil temperatures lower than +3° C of water saturated soils reduce the surviving chance
of slugs and snails in winter. In periods with favourable weather conditions for slugs the slug
activity density reacts faster and reaches higher values in the no till plots.

93-97

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Application of Phasmarhabditis hermaphrodita (Nemaslug®)
to commercial broad acre crops

Andrew P. Brown, Anthony Barker, Anthony Hopkins & David Nelson

Abstract: The mollusc specific parasitic nematode Phasmarhabditis hermaphrodita (Nematoda:
Rhabditida) has been shown to infect and kill a number of economically important pest slug and
snail species. This beneficial nematode is available commercially under the trade name
Nemaslug® (Becker Underwood Ltd., Littlehampton, UK). Use of this biological control agent by
large commercial growers is increasing. This increase in use also includes expanding from its
traditional markets in higher value salads, to broad acre vegetables such as potatoes. Use of
P. hermaphrodita has increased in recent years on outdoor crops due to a number of factors.
Firstly additional products are often needed to compliment the available chemicals (e.g.
Methiocarb, Metaldehyde and Ferric phosphate) in sub-terranian environments where they are
often not as effective. Secondly there is a drive for more environmentally sensitive farming
practices of which biological control, as part of an integrated pest management program, is an
important component.
This expansion into new markets, such as potatoes, has presented a number of challenges in
applying these microscopic worms. Application of these soft bodied nematodes now needs to be
carried out to large areas over long periods of time. To enable a grower to be able to do this,
nematode specific application equipment has been developed. The Wroot water Nemaslug Xtra
applicator is an injection unit which, whilst being able to inject nematodes into irrigation water
for a boom or gun, can keep the nematode solution constantly agitated and supplied with oxygen.
This system has been shown to be able to keep the nematodes alive and mixed in suspension for
over 24 hours. This equipment allows a grower the increased flexibility of no longer having to
wait for rain to apply and reduced application labour costs by not having to spend time spraying
P. hermaphrodita onto the crop with a tractor mounted boom.
The Wroot water Nemaslug Xtra applicator is the first ever piece of nematode specific
application equipment developed. This equipment has been designed, built and made available
for commercial growers, specifically for use of applying the biocontrol agent P. hermaphrodita
(Nemaslug® Xtra) to broad acre vegetable crops.

99-104

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The molecular detection of slow worm (Anguis fragilis) predation on slugs
David S. Brown & William O. C. Symondson

Abstract: Slow worm (Anguis fragilis) numbers are in decline due to habitat loss, modification
and fragmentation through agricultural intensification and urban development. While it is known
that slugs are a significant component of slow worm diet, slug species, and patterns of predation
on them, have not been studied before due to inherent difficulties of determining slug identity
through traditional methods of dietary analysis. In this study, a non-invasive molecular approach
was taken to detect slow worm predation on Deroceras reticulatum and Arion species, major
pests of agriculture, allotments and gardens. Slug DNA was detected in slow worm faeces
collected each month between April-September over two years from sites in Dorset and South
Glamorgan. Relationships between the consumption of slugs and slow worm sex, maturity stage,
snout-vent length and weight along with month, site, rainfall and temperature were assessed by
generalized linear models (GLM). Predation on slugs was high, with 45% of slow worms
(N = 400) found to have eaten them (22% D. reticulatum and 30% Arion). Predation on both
D. reticulatum and Arion was significantly affected by month, probably following changes in the
abundance / availability of slugs, with D. reticulatum predation also found to be positively
correlated with rainfall. In addition, predation on both D. reticulatum and Arion was positively
correlated with air temperature, when there is a greater abundance of slugs and when slow worms
are more active. Furthermore, a sex bias was found in predation on Arion, with female slow
worms more likely to have consumed them in April, May and September. This may reflect
different nutritional requirements of males and females. On a domestic scale, slow worms could
be encouraged to help suppress slug numbers on allotments and in gardens by the provision of
areas of rough grass and refugia (large stones / sheets of tin / carpet).

105-112

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Assessment of slug populations in grassland with permanent refuge traps
Maria Cordoba, Javier Iglesias, Jose Castillejo & Paula Ribadulla

Abstract: Surface refuge traps are recommended by researchers, consultants and manufacturers
of molluscicides to monitor slug density-activity in arable crops, but pastureland differs from
arable land with respect to many characteristics which play a major role in the slugs’ biology.
Here we report on the performance of non baited mat refuge traps permanently placed at the same
position over more than two years in established pasture, for the assessment of slug numbers and
biomass, in comparison with soil sampling and flooding over three days. Despite the availability
of alternative shelters provided by the vegetation, a great many slugs and slugs’ eggs were
registered in the traps over the year and over a wide range of temperatures under the traps.
Overall, traps showed the same trends as in arable land: traps showed a bias towards the larger
individuals and underestimated the numbers of the smallest slugs of each species (Deroceras
reticulatum (Müller), Deroceras panormitanum (Lessona & Pollonera), Deroceras laeve (Müller)
and Arion intermedius (Normand).

113-120

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Control of the water snail Lymnaea stagnalis in ponds
Albert Ester & Klaas Van Rozen

Abstract: In The Netherlands several plant growers, specialists on the production of water plants
such as Nymphaea alba and Nuphar lutea for the nurseries and home market, have problems with
the great pond snail Lymnaea stagnalis (Gastropoda; Lymnaeidae). Generally, these plants are
imported from outside Europe without any snails. During the production season of seedlings into
a more advanced stage plants are damaged by L. stagnalis, which is an increasing problem. The
damage consists of leaf damage or destroying the plants completely. Consequently, plants are
often no longer marketable. Normally damage appears in late spring until mid summer.
Plant growers using water from canals or other open surface water have serious problems, as
this water is contaminated with this species of snail and eggs. Growers using tap water do not
have snail problems. Nurseries do not accept plants with damage or any contamination with
snails or eggs. The consumers buy infected plants and their ponds have an ideal habitat for
multiplication of the snails.
Research is focused on the reduction of the water snail population without any impact on the
environment of the water organisms. Additionally, the products may not be phytotoxic to the
water plants.

121-126

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Birch tar oil is an effective mollusc repellent: field and laboratory experiments
using Arianta arbustorum (Gastropoda: Helicidae) and Arion lusitanicus
(Gastropoda: Arionidae)

Marleena Hagner, Lindqvist, I., Lindqvist, B., Tiilikkala, K., Penttinen, O.-P., Pasanen, T., & Setälä, H.

Abstract: Populations of two molluscs, the land snail Arianta arbustorum and the Iberian slug
Arion lusitanicus, have increased substantially in many places in the northern Fennoscandia in
recent years. In this study birch tar oil (BTO), a new biological plant protection product, was
tested against these molluscs. We examined whether 2 types of BTO, used either alone, mixed
together, or mixed with Vaseline®, could be applied as a repellent against 1) snails when painted
on a Perspex® fence, and 2) slugs when smeared on pots containing Brassica pekinensis
seedlings. Both the fences and the pots with seedlings were placed in each field with a high
population of the target organism. The BTO – barriers were effective in repelling both snails and
slugs. However, the repellent effect of BTO alone against the molluscs was short-term. Repeated
treatments were required to keep the slugs away from the plants and we found that the interval
between treatments should not exceed two weeks. Most noticeably, the BTO+Vaseline® mixture
prevented the land snails from passing over the treated fences for up to several months. The
results of these experiments provide evidence that BTO, especially when mixed with Vaseline®,
serves as an excellent long-term repellent against molluscs.

127-130

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Conservation tillage, field crops, and slugs in North America
Ronald B. Hammond

Abstract: Slugs are often problems in field crops grown using conservation tillage practices in
the eastern United States, as well as certain locations in the Midwest and the southern USA, as
well as in Canada. Although most concern has been on corn and soybean, reports of problems
from dry beans, cotton, oil-seed rape, sunflowers, winter wheat, and fall planted alfalfa are often
received. Although most problems are in fields located in the original forested areas of eastern
and southern USA, reports are also being received from the Great Plains’ grass lands of slug
issues in irrigated no-till fields. Overall, slug problems have increased in geographical area as
growers in the USA and Canada have adopted conservation tillage practices. As in other areas of
the world, determining new methods of slug control is of utmost importance in order to allow
growers to continue using conservation tillage practices. In areas that are new to slugs, a primary
concern is educating growers on IPM approaches to slug management.

131-133

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Perennial ryegrass seed treatment to control slug damage
Hilfred Huiting & Albert Ester

Abstract: Slugs are an important pest of grass seed production on marine loam soils. Significant
damage occurs from the start of germination until tillering, the main slug attack occurring at
emergence and shortly after. Slug attack causes plant loss resulting in open spots in the field
which in severe cases may cause significant yield loss. Predominantly baited molluscicide pellets
are used to control slugs in Dutch grass seed production however occasionally being applied
untimely resulting in repeated application or even unsatisfactory control. Four field trials in three
subsequent years and one semi field trial were carried out to test the efficacy of grass seed
treatments to protect the crop against slug damage. In the field trials treatments were compared
with both an untreated control and a reference treatment consisting of broadcast applications of
metaldehyde slug pellets at a rate of 448g a.i. per hectare. A field trial starting in autumn 2003
together with a field trial in 2004/2005 and an additional semi field trial in 2004 resulted in two
field trials testing metaldehyde at three application rates and thiacloprid at one rate, in 2005/2006.
Tested on heavy marine loam soils both metaldehyde at 360g and thiacloprid at 154g a.i. per kg
seed resulted in excellent crop protection, reduced application rates however showing efficacy as
well. Plant numbers as well as crop development figures were equal to or significantly higher
than the results of two applications of metaldehyde baited pellets. Results are discussed with
particular focus on the variation in results and possible variation in mode of action between
metaldehyde and thiacloprid.

135-145

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Is the mollusc Ena montana (Draparnaud, 1801) invasive or relict species
in Lithuania?

Viktorija Kuznecova & Grita Skujienė

Abstract: Usually invasive molluscs represent some of the world’s most important ecological
and economic pests which quickly and abundantly colonize habitats not typical for their
provenance. In this sense E. montana is local in the mountains of Alps, Carpathians, Sudeten
under 2800 m but in Lithuania it was found in the Northern Lithuanian Lowland. The first
finding of E. montana in Lithuania was made in 1958 by P. Šivickis and our data show that this
species is abundant in Biržai forest (maximum 314 individuals in one square meter). Conversely
we can assert that E. montana is post-glacial relict species of the Holocene because its
distribution in Lithuania have the most striking feature – it was found only in one location – in
one of the oldest woodland of Lithuania – Biržai forest. Regrettably we don‘t have fossil data
from this part of Lithuania and the implication above was made only after intensive molluscs
search in 238 localities of Lithuania during the Woodland Key Habitat Inventory in 2001-2005.
The differences in gleysols between other woodland sites in Lithuania are fractionally except for
twice bigger Mg2+ ions (30 mg/kg) and high humidity in Biržai forest. During the past few
decades Biržai forest was intensively exploited and melioration took place since 1960 till 2004.
Since all known places for E. montana are in the most humid central part of Biržai forest, what
prognosis can we make – will E. montana spread or decrease? The other question is, can we
associate this population with one from Latvia Gauja National park which is known for the
Devonian sandstone cliffs, in some places reaching 90 meters, along the banks of the Gauja river,
or mountains of Poland, where the nearest populations of E. montana can be found? All these
questions are under discussions.

147-154

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Testing the efficacy of different substances with a potential molluscicidal effect
under laboratory conditions

Žiga Laznik, Matej Vidrih & Stanislav Trdan

Abstract: We studied in 2008 and 2009 under laboratory conditions a molluscicide activity of 26
substances in 89 different treatments. Experiments, in which slugs (Arion spp.) were comprised,
took place in two series, namely with injection of active substance in slug intestine and
application of pellets. After conducting the injection we observed 100% mortality of slugs in
treatments with bacteria Bacillus thuringiensis var. kurstaki (0.25ml in 10% concentration/
individual), caffeine (0.25ml in 10% concentration/individual), sodium dodecyl sulphate (0.25ml
in 10% concentration/individual, 0.125ml in 10% concentration/individual, (0.125ml in 5%
concentration/individual, 0.0625ml in 10% concentration/individual) and pirimicarb (0.25ml in
10% concentration/individual, 0.125ml in 10% concentration/individual, 0.125ml in 5%
concentration/individual, (0.0625ml in 10% concentration/individual). Meanwhile application of
pellets gave the highest (100%) slug mortality when sodium dodecyl sulphate in 0.5%
concentration with caraway as a supplement was used.

155-160

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Snails, slime and sciomyzid flies – prey location in a malacophagous Diptera
Rory J. Mc Donnell, Collette J. Mulkeen & Mike J. Gormally

Abstract: The family Sciomyzidae is unique amongst insects in that almost all species are
exclusively malacophagous. Globally, this feeding behaviour has made the family a target for the
selection and assessment of biological control agents of snail intermediate hosts of trematode
diseases and of gastropod pests of agriculture and horticulture. Although a wide range of
information has been published on the life history of these flies, relatively little is known about
prey location mechanisms. In this study, the ability of neonate and third instar larvae of the
aquatic sciomyzid, Sepedon spinipes, to follow fresh and aged (45 minutes) snail mucus trails
was assessed using filter paper Y-mazes. When fresh mucus trails were used, all of the neonates
and third instar larvae displayed a positive response and followed the mucus trail into the
experimental arm. The stimulatory substance(s), however, appeared to become inactive with time
and after 45 minutes none of the tested larvae reached the trail end. These results suggest that
trail-following behaviour in Sciomyzidae is an innate response and that aquatic species may also
have the potential to forage for snails on shoreline and semi-aquatic areas.

161-165

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Energy balance of lettuce fed Arion ater/rufus (Biscay, Northern Spain)
throughout development

M. Mercedes Ortega-Hidalgo, Hugo Alejandro Núñez-García & Jesús M. Txurruka

Abstract: In temperate areas, the big terrestrial slug Arion ater reaches a considerable size within
a limited growing season (7 to 14 months) exhibiting remarkable growing rates. In this work,
energy balance of different size specimens of Arion ater sampled at distinct moments chosen to
portray the various developmental stages along its life cycle has been determined in the
laboratory through short-term experiments using lyophilized lettuce (Lactuca sativa) as foodstuff.
In addition allometric relationships of the various components of energy balance (ingestion,
absorption and, metabolic rates) have been established. Whereas mass exponent for oxygen
consumption is 1 within each developmental stage (metabolic expenditure scales proportionally
to body size provided animals belong to a similar growth phase) physiological descriptors related
to energy intake (ingestion and absorption rates) share a common correlation coefficient of 0,610
(± 0,130) the combination of both results explaining increased reduction of growth rates from
immature young phases to active growing males (IGR = 0.035 to 0.020mg/mg/d on dry weight
basis). Assimilation Efficiency has remained constant along the study being 60% of organic
uptake. Lettuce appears as a suitable food for Arion and SFG determined in the laboratory has
resulted in positive values for every developmental stage, including egg-lying females: 313 J/d
for young slugs, 934 J/d for males and 1646 J/d to 1452 J/d for October and November females
respectively. Integrated Mean Gross Conversion Efficiency (SFG/Ingestion) is 44.6% (±3.8). As
a conclusion, cumulative ingestion of a given slug from an initial size of ~3.5g live weight to a
full-grown female of ~23g would require about 600g of fresh lettuce.

167-172

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Hibernation and latitude in Helix (Cornu) aspersa: an attempt to integrate
environmental restrictions to active life, length of stasis endurance
and metabolic costs

Mercedes Ortega-Hidalgo, Iker Rodriguez-Zaldua & Jesús M. Txurruka

Abstract: Original data from a Mid-Atlantic population (43º19’) of Helix aspersa is discussed in
relation to literature and compared with the overlapping species Helix pomatia. An asymptotic
relationship relating length of hibernation period and latitude within temperate areas is described.
This simple model predicts maximal hibernation periods of 7.5 months and no hibernation
below~35ºN (r2= 0.89) for Helix aspersa. While lack or severe reduction of hibernation-linked
dormancy is usually accompanied by increased inactivity due to aestivation, maximal length of
hibernation in non-or scarcely aestivating populations would probably represent a fixed trait in
terms of supporting metabolic arrest that would be restricting the ability to inhabit colder areas
for this species.

173-177

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Vertical and horizontal movement by slugs
Gordon Port & Alain D. Craig

Abstract: Following treatment with molluscicides, slugs can recolonize a site very quickly, but
what proportion of the colonizing slugs move from adjacent areas (horizontal movement) and what
proportion from within the soil (vertical movement)? On a grassland site barriers were used to trap
and exclude slugs to estimate horizontal and vertical movement over a period of 32 months. For the
first 15 months vertical movement made a significant contribution to the slugs recolonizing the
area. The ecological mechanisms and the implications for control of slugs are discussed.

179-182

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Predation and scavenging by the generalist predator Pterostichus melanarius
Adam Powell, David Bohan, Alison Haughton, William O. C. Symondson & Jean-Francois Testut

Abstract: Pterostichus melanarius is a generalist predator that may be a significant predator of
slugs in arable ecosystems and therefore potentially part of an integrated pest management
programme against this pest taxon. A suite of field and laboratory experiments were conducted to
investigate feeding behaviour in this beetle, and its ability to reduce slug population size.
Experimental results suggest: (1) at the semi-field scale, P. melanarius did not reduce slug
density despite beetles being in a state of hunger. (2) The feeding activity of P. melanarius
changed according to the vital status of prey. (3) Conditioning of P. melanarius to specific food
types had little effect on subsequent feeding behaviour. Dietary conditioning only affected their
subsequent propensity to feed on seeds.

183-187

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Does paternity influence slug growth rate?
Lisa Redford, Kirsten Wolff & Gordon Port

Abstract: Slugs from the same batch of eggs may exhibit very different growth rates. Initial egg
size and food availability do not seem to be the cause. We investigated slugs from the same egg
batch using microsatellites to look for differences in the paternity of eggs within a single batch.
There was no evidence to suggest that differing paternity was the reason for the different growth
rates of embryos from the same mother.

189-191

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Neu 1184: A new bait to control the Golden Apple Snail (Pomacea canaliculata)
in rice cultivation

Reinhard Arndt & Andreas Prokop

Abstract: The tropical sweet water snail Pomacea caniculata (Golden Apple Snail) from South
America was introduced to Asia as a potent protein source. Unfortunately this snail failed as a
food source but was released into the environment and has become a serious pest in rice
cultivation. An economical relevant damage occurs through the feeding of the snails on the
young leaf tips of rice plants within the first 14 days after transplanting or emergence of the
seedlings. Besides mechanical protection methods various chemical products, most of them
without an official registration, are currently used to control the Golden Apple Snail. Moreover
baits with the molluscicidal active metaldehyde are applied. The company Neudorff
manufactures and sells slug baits (Ferramol, Sluxx) with the active iron phosphate for the control
of land slugs and snails. In order to evaluate if the active iron phosphate has also a potential to
control the Golden Apple Snail a rearing system for this aquatic snail was established and
different tests system were developed. The formulation of the current bait was optimized for the
control of aquatic snails. The new bait is stable in water and thereby suitable to control aquatic
snails like the Golden Apple Snail. Own tests have shown that the new bait is as efficacious as
currently sold metaldehyde baits. At present comprehensive field tests are under way in Asia to
assess the efficacy of the environmentally friendly iron phosphate bait in rice cultivation.

193-197

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Food consumption and activity in Deroceras reticulatum and Cantareus aspersus
Paula Ribadulla, Javier Iglesias, Jose Castillejo & Maria Cordoba

Abstract: Activity and food consumption were simultaneously monitored in populations of
known density (20 or 40 animals m-2) and biomass of adult slugs Deroceras reticulatum (Müller,
1774) and adult snails Cantareus aspersus (Müller, 1774), kept in mini-plots under semi-natural
conditions. Food consumption of turnip roots was monitored daily in terms of dry weight. The
activity of the populations was monitored using time-lapse video techniques to record the
movements of the animals. To obtain a comprehensive measure of the activity over the time
course, the numbers of active and feeding animals registered at 30 min intervals were integrated
over time using the formula for the calculation of the “area under the disease progress curve”
(AUDPC), thus allowing expressing the intensity of activity and the intensity of feeding activity
of the populations by single values over each 24-hours period. Daily food consumption per gram
of biomass was independent of population density for both species, and it was nearly 3 times
larger in the slug than in the snail; however, food consumption per plot was nearly 10 times
larger in the snail because of their bigger size. On average, the activity level over the year was
higher and less variable in D. reticulatum populations than in C. aspersus populations. The daily
intensity of activity and daily intensity of feeding activity showed significant correlations between
them and with food consumption (g d.w./g biomass/day), but activity explained only a limited
amount of the variability in food consumption.

199-205

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Seasonal changes in feeding rates and respiratory metabolism in two cohorts of
Helix aspersa (Müller) across an extreme heat wave: laboratory and field studies

Iker Rodriguez-Zaldua, Jesus M. Txurruka & Mercedes M. Ortega-Hidalgo

Abstract: Seasonal evolutions of organic growth rates, metabolic rates and organic assimilation
rates of two actively growing age classes of brown garden snail (Helix aspersa) from a wild
population have been studied during 2003-2004. Organic growth rate was calculated for each age
class as differences between samplings divided by time elapsed. Maximal rates were observed
throughout the spring season once snails had aroused from hibernation (~50 to 100J d-1). An
extreme heat wave induced an aestivation period associated to weight loss (in September minimal
growth rates are recorded: ~ -15.7 to -24.7J d-1) degrowth increasing in smaller animals. Positive
net growth was recovered in autumn before the hibernation period, activity being resumed in the
next spring. Continuous increase of metabolic rate observed during the spring, due mainly to
individual weight gain (effects of temperature increase being exclusive to the month of June)
allows higher activity levels and subsequent higher ingestion and assimilation rates. Maximal
assimilation rates occur in July: 225J d-1 for young immature snails and 360J d-1 for adult
reproductive specimens. Minimal and maximal routine metabolic rates of active snails recorded
in this study oscillate between 25 to 60J d-1 in April (for non-reproducing and mature snails
respectively) to 175 to 275J d-1 in August. Although oxygen consumption of hibernating snails
was not recorded, values registered at the peak of negative organic growth rate in mature snails
could be taken as an approaching value: 25.8J d-1 animal-1. Since 114.7J d-1 animal-1 can be taken
as winter active metabolic rate acute metabolic depression would represent 22.5% of that of
active snails at the onset of hibernation. A 3 month period of hibernation seems to occur
repeatedly (2005, 2006), whereas the recorded aestivation period was unexpected, being
attributed to the singular weather conditions during the summer of 2003, indicating that Helix
aspersa dwelling in this locality would behave as facultative aestivators.

207-211

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Detecting introduced species in the slug fauna of the British Isles
Ben Rowson & William O. C. Symondson

Abstract: The problems of discriminating native from introduced slug species in Britain and
Ireland, and of knowing the existing fauna so that future introductions are detected, are discussed.
To help resolve these, we suggest the slug fauna should be taxonomically clarified, genetically
screened for known pest lineages, and the public profile of slugs, raised to promote vigilance.

213-218

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Slugs from the Nearctic: what we need to learn from the Western Palearctic
Anna K. Thomas, Rory J. Mc Donnell & James D. Harwood

Abstract: The increase in slug biological control research over the last twenty-five years has
been prolific throughout much of the Western Palearctic region, leading to a literature replete
with examples of pest management recommendations. In contrast, the Nearctic region suffers
from a limited knowledge of the ecology, biology, distribution, and impact of slugs throughout
the entire ecozone, despite the area supporting a rich exotic fauna and several genera endemic to
the region. Consequently, management options are limited, new invasive species are often
unreported, and agricultural productivity is regularly impacted due to limited control options and
the lack of robust guidelines for growers. This has been exacerbated by increases in global trade
and movement of produce and horticultural materials within North America, facilitating the
dispersal of exotic molluscs to new areas. In this paper, we will provide a brief overview of the
status of exotic and native molluscs in North America, paying particular attention to the diversity
of crops throughout the Nearctic and identifying those areas with greatest probability for
experiencing slug damage at economically significant levels. Detailed information on the source
location of exotic slugs invading the Nearctic from the western Palearctic is also presented using
Arion subfuscus as a case study. To conclude, we refer to the literature from the Western
Palearctic to aide us in considering options for biological control and prioritizing malacophagous
natural enemies for future research efforts in the Nearctic.

219-222

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Molluscs in defense: Cellular and sub-cellular mechanisms in snails and slugs
to cope with stress

Rita Triebskorn & Alexandra Scheil

Abstract: The paper reviews cellular and subcellular mechanisms which are – among possible
others – responsible for the relative robustness of molluscs under stressful environmental
conditions (e.g. chemical or mechanical stress, extremely high and low temperature, drought, or
changes in the pH). It provides several explanations why representatives of this animal group are
capable to survive even under severely polluted conditions, and why others are capable to tolerate
or neglect impacts of possible molluscicides.

223-226

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Influence of life cycle and food quality on polysaccharide and total carbohydrate
content of the body wall and genitalia of Arion ater L. (Gastropoda: Pulmonata)

Jesus M. Txurruka & Mercedes M. Ortega-Hidalgo

Abstract: Carbohydrate and polysaccharide contents in Arion ater are highly dependent on stage
of the life cycle (male (August) or female (November)), type of carbohydrate in the food (starchy
or non-starchy foods) and tissue (body wall (BW) or genitalia (G)). Carbohydrates accounted for
nearly a 37.3% of the dry weight (DW) of body walls of male slugs fed in the lab for 10 days on
starchy foods, whereas that content lowered to 21.5% of DW of BW of female slugs. When slugs
were fed for the same period on foods lacking starch, carbohydrate content (CC) of BW lowered
to 13.6% of DW in male slugs and dropped to 6.9% of DW in females. Regarding genitalia, CC
of reproductive tissues in female slugs was 42.0% of DW when slugs were fed on starchy foods,
and a mere 27.8% of DW when fed on or non-starchy foods. Most of the carbohydrates seem to
be polymerized, because polysaccharides stand for ≈57% of the carbohydrates in BW of both
male and female slugs fed on starchy foods. When slugs were fed on non-starchy foods,
polysaccharide percentage reduced to 42.3% of the carbohydrates in males and, as it could be
expected, diminished more in females, where polysaccharides represented only a 30.6% of the
carbohydrates. In genitalia of female slugs the carbohydrates were primarily in their polymerized
form, but their percentages did not depend on the amount or on the type of carbohydrate present
in food.

227-233

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Slug damage in potatoes in The Netherlands
Klaas van Rozen & Albert Ester

Abstract: At times, slugs are reported causing severe damage in potato tubers on loess soils.
Tubers show relatively small holes and larger cavities inside. Slime and occasionally slugs are
observed. Damaged tubers are not saleable and severe affected lots of potatoes are rejected from
the market. The moment when farmers observe damage is rather late and control actions are
limited. In contrast to the British situation, studies on slug species responsible for potato damage
in The Netherlands have been underexposed. Neither control strategies nor factors influencing
slug population densities have been investigated regarding the specific species. In 2009 a
preliminary study was started aiming at finding the slug species responsible and make an
inventory of factors with a possible relation to slug population dynamics. Farmers facing
problems with slugs have been visited and were exposed to an extensive questionnaire. Fields
where damaged potatoes were harvested were compared to fields lacking any slug damage.
Subsequently farmers suffering no slug damage in potatoes at all have been exposed to the same
questionnaire. Both target growers were questioned on experiences with slugs, control methods
and crop production management. The results with ‘soft’ conclusions are discussed.

233-240

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