Lyon Meeting

A meeting of this sub-group of the International Organisation for Biological Control was held in Lyon, France, on 8th and 9th March 2001, at the Institut Supérieur d’Agriculture Rhône-Alps, organised by André Chabert, Séverine Pelcoq and David Glen. About 50 delegates from 8 countries heard 26 presentations on slug and snail biology, integrated management, and biological control with rhabditid nematodes and other organisms. The meeting showed vigorous advances in our understanding of slug and snail dynamics, ecology and ecophysiology.

The Mediterranean snail Microxeromagna armillata is a pest in citrus orchards in SE Australia (Angela Lush and Dennis Hopkins, Adelaide). Suzanne Charwat and Valerie Kempster (Adelaide) studied the thermal tolerance of ‘white snail’ pests in grain, where stubble management is increasingly used for snail control by forcing snails onto the hot ground, but with variable results. They also reported on integrated use of mechanical stubble management, chemical controls and a parasitic fly Sarcophaga penicillata; the last is particularly active against Cochlicella barbara, the most difficult species to control. Adel El Titi (Stuttgart) found no consistent correlation between yield of oil seed rape and tillage regime, and number of trapped D. reticulatum was affected only by molluscicidal treatment. Louise Simms, Mike Wilson and Mullins (Aberdeen), investigating seed dressings to control oilseed rape damage by slugs, encountered some problems with phytotoxicity, although metaldehyde dressing at 33 g ai/kg seed gave good control. Xavier Iglésias, José Castillejo and others at Santiago showed a range of organic or plant-derived pesticides were effective against eggs of D reticulatum in laboratory tests. Constanze Kuckuck (Bayer AG) described responses of Deroceras reticulatum to volatile attractants of conspecifics or their foot mucus, particularly to dimethyl disulphide and trisulphide.

Alan Craig, Gordon Port and Shirley (Newcastle), by comparing permanent and temporary traps, found little evidence of horizontal movement by Deroceras, but significant vertical movement through soil. David Bohan, David Glen, Chris Wiltshire and Louise Hughes (Long Ashton) found seasonal differences in the spatial distributions of A. intermedius and D. reticulatum using different distances between sampling points. Yoon Hong Choi, described another population study at Long Ashton, applying differential equations incorporating the concept of day-degrees accumulation. Gordon Port and Jacqui Mair, and Ingo Schuder, Port and Bennison (Newcastle) reported on two collaborative schemes. One to forecast slugs in lettuce and Brussels sprouts based on population dynamics, and another on slug and snail damage in hardy ornamentals – an ADAS survey has shown Deroceras panormitanum (D. caruanae) and Oxyloma pfeifferi to be the most abundant slug and snail species.

Sabine Diwo, di Pietro and Auger (Critt-Innophyt, Orleans and University of Tours) showed that field margins have a positive impact on slug control by carabid beetles. Bill Symondson (Cardiff), Rhian Thomas and David Glen, having noted that slugs sometimes decline markedly in autumn when larvae of the carabid Pterostichus melanarius are high, found that the larvae significantly reduce slug numbers and biomass in semifield conditions. Mair and Port showed that when P. madidus were present, D. reticulatum spent less time foraging, and moved faster; although no slugs were killed in the experiments, the results suggest that crop damage would be reduced. Tom Franks’ team (Bern) found that Pterostichus melanarius destroyed slugs’ eggs and hatchlings, but preferred those of D. reticulatum to A. lusitanicus. Poecilus cupreus would only eat eggs and hatchlings if no alternative food was provided. They also found that weeds reduced slug feeding, although, where weeds compete with the crop, there may be loss of yield.

Bernhard Speiser (Research Institute for Organic Agriculture, Frick) calculated that where Arion lusitanicus were the pest species in organic horticulture, the highest profit margin was obtained with iron phosphate alone, although iron phosphate in combination with nematodes (Phasmarhabditis hermaphrodita) gave better control. The situation might change if Deroceras were the principal pest, or if nematode treatment were to become cheaper. Iglesias, Castillego and others found that P. hermaphrodita reduced slug damage to horticultural and ornamental crops, except if recently manured, but metaldehyde and iron phosphate were as or more effective. Rik de Werd, Albert Ester and others (Lelystad) showed that P hermaphrodita nematodes are unable to infect slug eggs, but reduced feeding especially in smaller individuals. Mike Wilson (Aberdeen) and colleagues from Long Ashton showed that P hermaphrodita treatment had no detectable effect on any of seven snail species present in margins of an oilseed rape crop (Monacha cantiana , Cepaea hortensis and C. nemoralis, Pomatias elegans, Oxychilus helveticus, Clausilia bidentata and Discus rotundatus). In lab. trials, significant mortality was seen only in M. cantiana and D. reticulatum. David Glen and others investigated combinations of slug-parasitic nematodes with other, mechanical controls in organic vegetable crops – fibre matting was useless, but 9V electrical barriers were very effective. Hand removal also gave good results, and was needed when electrical barriers enclosed a large area. Ester and Klaas van Rozen showed that nematodes and metaldehyde gave comparable control of D reticulatum damage to green asparagus. Natalia Vernava and others at Long Ashton reported that slug damage to Chinese cabbage was increased by build up of slug numbers under preceding cover crops of red clover or vetch, but nematode survival was not influenced by any build up of nematode antagonists in the cover crop.
The variable effectiveness of P. hermaphrodita treatments has stimulated two lines of study. Keith Davies, I Mazet and Colin Denholm (Rothamsted) have developed monoclonal antibodies to follow the fate of P. hermaphrodita after it is applied to the soil. Susan Coe (Long Ashton) and collaborators in an EU project have collected and tested 30 new strains at various European sites, and four new strains which consistently performed well will be evaluated further.

The social entertainment which has become a characteristic of these ‘slug meetings’ was well up to standard, with a final afternoon tour of a wine museum, a Beaujolais tasting, and dinner entertainment by the Band ‘Baujol – in which the band strapped themselves into wheeled trolleys laden with electronic musical instruments. At times, the band descended along the narrow aisles between the tables, cables trailing, and others urged us to form a conga line, augmented by members of a local political party from adjoining tables.

Bill Bailey


Fig. 1: Delegates of the IOBC meeting on Integrated Control of Slugs and Snails, outside Abbaye d’Ainay in Lyon.
Fig. 2: Delegates of the Lyon IOBC meeting dining with entertainment by the Band ‘Baujol.