Soil degradation increased incessantly in the Pampas region of Argentina, due to the intensification of agricultural activities, when carried out with conventional tillage (CT) systems. No-tillage system was adopted as conservation practices by the farmers. The objectives of this study were: a) to determine the macrofauna taxa and their relative abundance under CT and NT in two different seasons; and b) to evaluate soil tillage and seasonal effects on the density of the main macrofauna taxa. The study was conducted from 2002 to 2004 in 46 production farms, in Balcarce, Argentina. Ten soil monoliths (25.2 cm side; 30 cm depth) ramdomly directed field at July-August; and at OctoberNovember to determine the number of individuals of macrofauna and Enchytraeidae. Soil macrofauna density did not differ between tillage systems. Oligochaeta Megadrilli density was generally not affected by the tillage system (P > 0.05) except in 2004 when it was greater under CT in July-August (P = 0.0002). Chilopoda density was greater in soils under NT, with significant differences in 2002 in October-November (P = 0.0070). In July-August of 2003 it was higher in CT (P = 0.0109). Diplopoda were more abundant only under NT in July-August 2004 (P = 0.0010). In July-August a significantly (P < 0.05) higher density of Enchytraeidae was found in CT than NT fields. No differences were observed in the taxonomic composition and the relative abundance of the macrofauna when comparing CT and NT. It can be then concluded that in the study region tillage systems affected slightly soil macrofauna and significantly Enchytraeidae.Additional key words: abundance, conventional tillage, no-tillage, soil invertebrates. ResumenEl sistema de labranza no afecta a la macrofauna en el sudeste de la provincia de Buenos Aires, ArgentinaEn la región pampeana argentina se ha producido una creciente degradación del suelo debido a la intensificación de las actividades agrícolas llevadas a cabo con sistemas de labranza convencionales (LC). Los agricultores, como práctica conservacionista, han adoptado la siembra directa (SD). Los objetivos de este estudio fueron determinar los taxa de la macrofauna y su abundancia relativa bajo LC y SD en dos estaciones diferentes y evaluar los efectos de los sistemas de labranza y estaciones sobre la densidad de los principales taxa de la macrofauna. El estudio fue llevado a cabo desde 2002 hasta 2004 en 46 lotes de producción en Balcarce, Argentina. En cada lote se tomaron diez muestras de suelo al azar (de 25,2 cm de ancho y 30 cm de profundidad) en julio-agosto y octubre-noviembre para determinar el número de individuos de la macrofauna y de los Enchytraeidae. La densidad de la macrofauna no difirió entre sistemas de labranza. La densidad de Oligochaeta Megadrilli no fue afectada por el sistema de labranza (P > 0,05), excepto en 2004 cuando fue mayor bajo LC en julio-agosto (P = 0,0002). La densidad de Chilopoda fue mayor bajo SD, aunque solo se observaron diferencias significativas en octubre-noviembre de 2002 (P = 0,007...

Management of the grey slug, Deroceras reticulatum (Müller) (Pulmonata: Stylommatophora), in Argentina, has been limited to the use of pelleted toxic baits containing metaldehyde. The most important molluscicides in the Argentinean market are Clartex (Rizobacter Argentina S.A.), Acay (Acay Agro S.R.L.) and Babotox (Huagro S.A.). The aim of this work was to investigate the efficacy and dose of those commercial baits against D. reticulatum. The molluscicides (Acay, Clartex and Babotox), at doses of 3, 4 and 5 kg ha -1 and dry and moist soil conditions were investigated in terraria trials. The efficacy of the molluscicides and dose level was also evaluated in field experiments at two sites at Balcarce in the southeast of Buenos Aires Province, Argentina. The proportions of dead slugs did not show significant interactions between soil conditions, molluscicides and their dose (p > 0.05). The proportion of dead slugs, in moist conditions, was significantly lower than under dry conditions (p < 0.05). Highest slug deaths were obtained with Acay 56.1%. The trend in relation to the efficacy of the molluscicides was similar in the two field trials. Acay gave the best performance, followed by Clartex and Babotox.Additional key words: commercial molluscicides, control efficacy, slug, soil conditions. ResumenEficacia de tres cebos con metaldehído registrados en Argentina, en el control de Deroceras reticulatum (Müller) (Pulmonata: Stylommatophora) En Argentina, el manejo de la babosa gris Deroceras reticulatum (Müller) (Pulmonata: Stylommatophora) está limitado al uso de cebos tóxicos formulados como pellets con metaldehído. Los molusquicidas más importantes usados en el mercado argentino son Clartex (Rizobacter Argentina S.A.), Acay (Acay Agro S.R.L.) y Babotox (Huagro S.A.). El objetivo del presente trabajo fue investigar la eficacia y dosis de los cebos comerciales sobre D. reticulatum. En el laboratorio se evaluaron molusquicidas (Acay, Clartex y Babotox), dosis (3, 4 y 5 kg ha -1 ) y condición del suelo (seco y húmedo). La eficacia de control de los molusquicidas y sus dosis se evaluaron en dos sitios ubicados en Balcarce (sudeste de la provincia de Buenos Aires, Argentina). La proporción de babosas muertas no mostró interacción significativa entre condición del suelo, molusquicida y dosis (p > 0,05). En condiciones húmedas la proporción de babosas muertas fue significativamente menor que en condiciones secas (p < 0,05) y la mortalidad mayor se obtuvo con Acay al 56,1%. La eficacia de los molusquicidas mostró una tendencia similar en los ensayos a campo y el producto más promisorio fue Acay seguido por Clartex y Babotox.Palabras clave adicionales: babosa, condición del suelo, eficacia de control, molusquicidas comerciales.

Importance of diet in the growth, survivorship and reproduction of the no-tillage pest Armadillidium vulgare (Crustacea: Isopoda)Importancia de la dieta en el crecimiento, la supervivencia y la reproducción de Armadillidium vulgare (Crustacea: Isopoda) plaga en siembra directa ABSTRACTThe studies of Armadillidium vulgare as pest are virtually null worldwide. However under no-tillage systems this species has found an adequate environment for its development and it has become an important pest in some crops in Argentina. It has been shown that the composition of vegetables affects the isopods biology. Our hypothesis was that soybean leaf litter has high nutritive value which allows A. vulgare to grow faster, survive longer, and have higher fecundity favoring the population increase and turning it into a crop pest. Growth and survivorship of juveniles and adults, egg incubation period, offspring number per female and offspring mean body weight were determined in individuals fed with leaf litter of soybean, sunfl ower, wheat and pasture. The growth rate coeffi cient, k, in juveniles was higher for soybean, intermediate for pasture and lower for sunfl ower. Adult growth was faster under the soybean diet. Survivorship under soybean and pasture was longer than under sunfl ower and wheat in both juveniles and adults. The reproductive parameters were similar in all diets, food did not generate any change in the reproductive aspects of A. vulgare. Results of the present study represent a source of information about the A. vulgare biology under different diets of agricultural origin to establish the basis for Integrated Management of this species as pest. Under soybean litter provision A. vulgare found the best conditions for faster growth, longer survival and relatively higher fecundity. In fi elds with soybean as preceding crop or in systems with high frequency of soybean in the crop rotation a more abundant population of A. vulgare would be found as well as with larger individuals which could cause more damage to the following crop in the rotation.Key words: crop leaf litter, food quality, herbivore, N content. RESUMENLos estudios sobre Armadillidium vulgare como plaga son virtualmente nulos a nivel mundial. Sin embargo, en los sistemas bajo siembra directa esta especie ha encontrado un ambiente adecuado para su desarrollo y se ha convertido en una plaga importante en algunos cultivos en Argentina. Se ha demostrado que la composición de los vegetales afecta la biología de los isópodos. Nuestra hipótesis fue que los residuos vegetales de la soja tienen un valor nutritivo alto lo cual permite a A. vulgare crecer más rápido, sobrevivir más y tener una fecundidad elevada favoreciendo el incremento poblacional y convirtiéndolo en plaga de cultivos. El crecimiento y la reproducción de juveniles y adultos, el período de incubación, el número de crías por hembra y el peso medio de las crías fueron determinados en individuos alimentados con residuos de soja, girasol, trigo y pastura. El coefi ciente de la tasa de crecimiento, k...

In the southeast of Buenos Aires Province (Argentina), slugs cause reductions in crop yield by killing seeds and seedlings, by destroying stems and growing points, and by reducing leaf area. Deroceras reticulatum (Müller, 1774) was introduced into Argentina a long time ago, but the biology and ecology of this species in this country are still unknown. The aim of this study was to determine how temperature affects growth rate, reproduction and survival of D. reticulatum and also to assess the seasonal phenology of this species. The life cycle of D. reticulatum was investigated at 12ºC, 20ºC and at a temperature which alternated between 12ºC for 16 h and 20ºC for 8 h. The light/dark regime during the experiment was LD: 8/16 h. Slug populations were sampled from grassland located at the Experimental Station of INTA Balcarce. Eggs hatched after 16.3 to 39.8 days and fertility varied between 83.9% and 91.1%. The mean time from hatching to oviposition was longer and fecundity lower at 20ºC than 12ºC and 12/20ºC (p <0.05). The net reproductive rate was 1.49 to 70.53 and the mean generation time varied between the 27 and 30 weeks. In natural conditions, eggs of D. reticulatum were found from early winter until the end of the spring, when soil temperature was 8-15ºC and humidity was above 15%. These results indicate that D. reticulatum has one generation per year, univoltine phenology, with peak densities of slugs from the beginning of winter to the end of spring, which coincides with the sowing and emergence of winter and summer crops.

The marsh slug Deroceras laeve (Müller) (Pulmonata: Stylommatophora) was recently introduced into the southeast of the Buenos Aires Province of Argentina, and has become one of the main pests of cropping systems under no-tillage management. The growth, survival, and reproduction of D. laeve were monitored at 12 deg C and 20 deg C to determine the most appropriate thermal conditions for its development. A sigmoid model (Y=A/(1+e**(B+Cx))) was used to describe the relationship between postembryonic development and temperature. At the beginning of development, the growth rate was lowest at 12 deg C but after the inflection point (21/2 months) was lower at 20 deg C than at 12 deg C. The slugs showed a higher mean body weight at 12 deg C (936.2 mg +/- SE 18.96) than at 20 deg C (409.4 mg +/- SE 16.02). Significant differences were seen in the mean incubation period at the different temperatures, as well as in the hatching rate, the duration of the preoviposition and oviposition periods, the number of eggs per clutch, and longevity; no differences were seen, however, in terms of mean fecundity. The incubation period was 35.3 and 16.03 days and the hatching rate 89.2% and 66.4% at 12 and 20 deg C respectively. At 20 deg C, longevity was less than half (21.9 weeks) that recorded at 12 deg C (54.4 weeks). At both temperatures the net reproductive rate (R sub(0)) was similar, but at 12 deg C the population increased 400 times in 33.1 weeks (T), while at 20 deg C it increased 359 times in half that time (T=16.5 weeks). These results show that, in the Buenos Aires Province, D. laeve produces two generations per year.