Three years trials were carried out to evaluate the efficacy of some molluscicides for the control of slugs (Arion sp.) and snails (Cepaea nemoralis and Helix aspersa) on organic lettuce in Emilia-Romagna (Italy). Iron phosphate has proven to be as effective as those based on metaldehyde. The nematodes Phasmarabditis hermaphrodita did not work against individuals as big as those employed in the trials

Censi, D

Curto, G

Gengotti, S

English

Organic Eprints

16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 Archived at http://orgprints.org/view/projects/conference.html   Evaluation of active ingredients and nematodes against slugs and snails on organic lettuce Gengotti S.1, Censi D. 1, Curto G. 2 Key words: snails, slugs, iron phosphate, metaldehyde, P. hermaphrodita Abstract Three years trials were carried out to evaluate the efficacy of some molluscicides for the control of slugs (Arion sp.) and snails (Cepaea nemoralis and Helix aspersa) on organic  lettuce  in  Emilia-Romagna  (Italy).  Iron  phosphate  has  proven  to  be  as effective  as  those  based  on  metaldehyde.  The  nematodes  Phasmarabditis hermaphrodita did not work against individuals as big as those employed in the trials. Introduction Terrestrial gastropods, mostly slugs (Arion spp., Deroceras spp., ecc.) and snails, may cause  severe  damages  to  a  vast  number  of  horticultural  crops  such  as  lettuce, cabbage,  strawberry  and  fennel  during  wet  periods  in  spring  or  in  autumne.  The problem  is  higher  in  organic  farms  where  these  organisms  find  a  favourable environment thanks to the presence of organic infrastructures and the prohibition to use chemicals of synthesis such as herbicides and insecticides. Agronomical  preventive  techniques  are  very  important  to  reduce  the  amount  of gastropods in cultivated fields, but they are not sufficient to avoid the presence of damages on sensitive crops such as lettuce or other vegetables. For this reason, in some  crucial  periods,  it  is  necessary  to  use  specific  molluscicides  such  as metaldehyde.  This  active  ingredient,  even  if  not  natural,  is  allowed  in  organic agriculture only in traps so with limited efficacy. The aim of the trials is the evaluation of the effectiveness of some alternative molluscicides that could be applied directly on fields or crops such like is done for iron phosphate or Phasmarabditis hermaphrodita. Materials and methods In  the  years  2003-2007  four  randomized  block  trials  have  been  conducted  in  an organic farm located in Sala di Cesenatico (FC), in Emilia-Romagna region, Italy. The aim was the evaluation of the effectiveness of some molluscicides allowed in organic agriculture  against  slugs  and snails  on  lettuce.  Table  1 shows  the most  important features of the trials. Every plot was made by a wodden cage of 1 m2 base and 0,5 m high  as  described  by  Maurin  and  Lavanceau  (1988).  To  avoid  the  escape  of gastropods the cages have been protected by an anti-insect net. In every plot 9-10 plants were transplanted on a soil layer 5 cm deep. Molluscicides applications and gastropods disposal in the cages was made 1-3 weeks after transplanting. The slugs and snails used in the trial were collected in the surrounding fields, immediately before                                                  1 Astra – Innovazione e Sviluppo s.r.l., Via Tebano, 45 – 48018 Faenza (RA). E-mail: gengotti@crpv.it; 2 Servizio fitosanitario - Regione Emilia-Romagna – Bologna (Bo).  16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 Archived at http://orgprints.org/view/projects/conference.html   the beginning of the trials. The trials focused on Arion sp., Cepaea nemoralis and Helix aspersa. The products and active ingredients or biocontrol agents tested are listed  in  table  2.  The  metaldehyde  based  products  used  in  trials  1-3  and  4  were different: dry formulated (Gastrotox E) or wet formulated (Mesurol M plus). To evaluate gastropods mortality 7-10 slugs and snails per plot have been empoyed. Crop assessments were done on 60-200 leaves of lettuce estimating the eroded leaf surface. The statistical analysis has been made, after the transformation of percentage data in angular values, by variance analysis (Anova) and mean comparison test (LSD con P ≤ 0,05). Tab. 1: main features of the trials   Trial 1  Trial 2  Trial 3  Trial 4 Year  2003  2004  2004  2007 Place  Sala di Cesenatico (FC) Cultivar of lettuce  Diabless  Mafalda Transplanting date  24-Sep  12-May  18-Sep  3-Sep Experimental layout  randomized block - 4 replications Plot size (m2)  1  1  1  1 Number of applications  1  1  2  1 Appications date  30- Sep  18-May  11-Oct, 20-Oct  5-Sep Number of plants/plot  9  10  10  10 Number of slugs/plot  4  -  10  10 Number of snails/plot  3  10  -  - Tab. 2: products details Dose  Product  Active ingredient  or organism A.i. content (% or unit/g) product (g/ha) a.i. (g/ha or unit/m2) Trial Nemaslug  P. hermaphrodita  6 x 105  6.300  300.000   1, 2, 3 Ferramol  iron phosphate  1  50.000  500  1, 2, 3, 4 Gastrotox E  metaldehyde  5  10.000  500  1, 2, 3 Mesurol M plus  metaldehyde  5  10.000  500  4 Results The results of the trials are shown in tables 3 and 4.  Trial 1 (autumn 2003) The trial period has been very dry. The product containing iron phosphate (Ferramol) was as effective as that containing metaldehyde (Gastrotox E) on both slugs and  on snails.  In  our  experimental  conditions  the  use  of  nematodes  of  species  P. hermaphrodita  (Nemaslug) couldn’t  permit  to  obtain  any  differences  in comparison with the untreated check. 16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 Archived at http://orgprints.org/view/projects/conference.html    Trial 2 (spring 2004) The trial period has been rather dry. Both iron phosphate (Ferramol) and metaldehyde (Gastrotox E) have been effective against snails even if the second one was slightly more performing than the first one. No dead snails have been found among those treated  with  P.  hermaphrodita  (Nemaslug),  but  a  significative  decrease  of  leaves damages, compared to the untreated check, has been reported. Tab. 3: average results Means marked by different letters on the same column are statistically different according to LSD test (P ≤ 0.05).  Trial 3 (autumn 2004) The trial period has been very wet and rainy. In our trial conditions iron phosphate (Ferramol) caused a higher slugs mortality than metaldehyde (Gastrotox E) even if leaves damages were comparable.   Trial 4 (autumn 2007) The trial period has been quite  wet. Both metaldehyde (Mesurol M plus) and iron phosphate  (Ferramol)  caused  a  high  slugs  mortality.  As  lettuce  damages  are concerned, the first molluscicide performed better than the second one. Tab. 4: average results Means marked by different letters on the same column are statistically different according to LSD test (P ≤ 0.05). Discussion In our experimental conditions the product based on P. hermaphrodita showed a very low molluscicidal activity. This may be caused, among other reasons, by the use of species of slugs and snails of big size.  Trial 1 (20-Oct-03) 19 DAT Trial 2 (10-Jun-04) 23 DAT Treatment dead slugs (%) dead snails (%) leaf eroded surface (%) dead snails (%) leaf eroded surface (%) 1  untreated  23.1   b  0   b  48.7  a  2.5  c  59.4   a 2  metaldehyde  100   a  91.7  a  0.9   b  82.5  a  0.3   c 3  iron phosphate  100   a  66.7  a  0.3   b  62.5  b  1.3   c 4  P. hermaphrodita  25   b  18.2  b  52.3  a  0  c  23.2   b Trial 3 (25-Oct-04) 5 DAT2 Trial 4 (21-Sep-07) 16 DAT Treatment dead slugs (%)  leaf eroded surface (%) dead slugs (%) leaf eroded surface (%) 1  untreated  12.9   c  20.6  a  17.2   a  24.2   a 2  metaldehyde  32.5   b  2.1  b  100   b  0.3   c 3  iron phosphate  86.8   a  0.6  b  89.7   b  6.3   b 16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 Archived at http://orgprints.org/view/projects/conference.html   Both iron phosphate and metaldehyde based molluscicides have shown an interesting activity even if it has to be noticed than the first one has been used at a product rate five time higher than the second one. In dry or very dry conditions (respectevely trials 2 and 1) metaldehyde has performed better than iron phosphate. In wet or very wet conditions  (trials  4  and  3)  iron  phosphate  performed  better  than  dry  formulated metaldehyde but slightely worse than wet formulated metaldehyde. The product based on iron phosphate could be an interesting tool to fight gastropods in organic farming as it can be spread directely on the crop, differently than metaldehyde.  Conclusions According to the results of the trials it is possible to state that:  the product based on nematodes P. hermaphrodita may be fit to be used in infestation conditions where little sized species of gastropods are prevalent but not against big sized individuals (Speiser et al., 2001; Grimm, 2002); the effectivenss of metaldehyde based products can vary upon formulation type. Wet formulated  products  have  to  be  preferred  to  dry  formulated  ones  (Henderson  and Triebskorn, 2002); the product based on iron phosphate has proven to be as effective as those based on metaldehyde but easier to be used in organic agriculture thanks to the possibility of spreading directely on crops (Arndt et al., 2004). Acknowledgments Activity carried out within the project co-ordinated by CRPV (I) in collaboration with ProBER, funded by Emilia-Romagna Region (L.R. 28/98) References  Arndt  R.,  Prokop  A.,  Puritch  G.,  Pederzoli  D.  -  2004  -  Esca  lumachicida  Ferramol:  nuovo molluschicida per il controllo di lumache e limacce. Atti 2°  Convegno sulla difesa delle colture in agricoltura biologica, Cesena, 23-24 Novembre 2004,  pag. 30. Grimm B. - 2002 - Effect of the nematode Phasmarhabditis hermaphrodita on young stages of the pest slug Arion lusitanicus. Journal of Molluscan Studies, 68, 25-28. Henderson I., Triebskorn R. - 2002 - Chemical Control of Terrestrial Gastropods. In: Barker G. M. (ed) Molluscs as Crop Pests. CAB International, Wallingford, UK. 576 pp. Speiser B., Glen D., Piggot S., Ester A., Davies K., Castillejo J., Coupland J. - 2001 - Slug Damage and Control of Slugs in Horticultural Crops. FiBL-Merkblatt. Research  Institute of Organic Agriculture (FiBL).    

Evaluation of active ingredients and nematodes against slugs and snails on organic lettuce

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