Résumé
This research reports the terrestrial slug Meghimatium pictum (Stoliczka, 1873) (Stylommathophora: Philomycidae) as an agricultural pest for the first time in Southern Brazil vineyards. The species was found in densities exceeding 20 slugs.m-2 in Vitis labrusca L. vineyards at six municipalities of the Southern Brazil's viticulture region. It causes damage a loss by leaving residual mucus on grapes and by consuming grapes already perforated by other organisms, such as insects or birds, or mechanically damaged by in situ compression. The effectiveness of iron phosphate and metaldehyde baits on M. pictum was evaluated in laboratory experiments. Iron phosphate bait was more effective in controlling M. pictum (70%) than metaldehyde bait (15%).
O presente trabalho relata pela primeira vez a lesma terrestre Meghimatium pictum (Stoliczka, 1873) (Stylommathophora: Philomycidae) como uma praga agrícola causando danos em vinhedos no Sul do Brasil. Esta espécie foi encontrada em densidades superiores a 20 lesmas.m-2 danificando uvas da espécie Vitis labrusca L. em seis municípios da região vitícola do Sul do Brasil. O impacto econômico causado por M. pictum está associado ao movimento dos espécimes no dossel da videira e nas uvas, provocando a contaminação residual por muco e o consumo de uvas já perfuradas por outros organismos, tais como insetos ou aves, ou mecanicamente danificadas pela compressão in situ. A eficácia das iscas a base de fosfato de ferro e metaldeído sobre M. pictum também foi avaliada em condições de laboratório. A isca a base de fosfato de ferro foi mais eficiente no controle de M. pictum (70%) do que a isca a base de metaldeído (15%).
Résumé
Soil properties and the environment have multiple outcomes on fungal communities. Although, the interaction effects between management intensity, pH, available phosphorus, organic carbon, soil texture and different fractions of water stable macro-aggregates on the communities of microscopic filamentous fungi (MFF), iron phosphate solubilizing fungi (PSF-Fe), and iron and calcium phosphate solubilizing fungi (PSF-(Fe+Ca)), have been previously evaluated in field conditions, this has never been performed in terms of their combined effects, neither with phosphate solubilizing fungi. To assess this, we collected 40 composite soil samples from eight Mexican and Colombian coffee plantations, with different management intensities and physico-chemical edaphic parameters, during 2008-2009. We isolated different communities of MFF, PSFFe and PSF-(Fe+Ca), by wet sieving and soil particles culture in Potato-Dextrose-Agar from soil samples, and we classified isolates in terms of their phosphate solubilizing ability. Following the principal component analysis results, we decided to analyze fungal communities and abiotic factors interactions for each country separately. Structural Equation Models revealed that organic carbon was positively associated to MFF richness and number of isolates (λ>0.58), but its relationship with PSF-Fe and PSF-(Fe+Ca) were variable; while the available phosphorus, pH and water stable macro-aggregate fractions did not show a clear pattern. Management intensity was negatively related to PSF-Fe (λ≤-0.21) morphotype richness and the number of isolates in Colombian coffee plantations. We found that the relationships of clay and organic carbon content, and available phosphorus and soil pH, with the species richness and number of isolates of MFF, PSF-Fe and PSF-(Fe+Ca) were highly variable; this made impossible to generalize the responses between saprotrophic fungal groups and geographic zones. The management intensity was not related to species richness and number of isolates of MFF in any coffee areas, while for PSF the relationship could not be defined. The different water stable macro-aggregates fractions did not show a defined pattern in relation to the species richness and the number of isolates of saprophytic and phosphate solubilizing fungi (PSF). This study highlights the need to take into account edaphic and geographic context in order to reach a better understanding of the intensity management effects on MFF and PSF function in agroecosystems.
El suelo y sus propiedades tienen múltiples relaciones con las comunidades fúngicas. El efecto conjunto de la intensidad de manejo y las variables edáficas, incluida la estabilidad de agregados sobre las comunidades de hongos microscópicos filamentosos (HMF), solubilizadores de fosfato de hierro (HSP-Fe) y solubilizadores tanto de fosfato de hierro como de calcio (HSP-(Fe+Ca)) no han sido evaluadas en campo. A partir de 40 muestras edáficas de ocho plantaciones de café de Colombia y México, con diferentes intensidades de manejo (IMPC) y con diferencias en sus variables edáficas, se aislaron y evaluaron las comunidades de HMF, HSP-Fe y HSP-(Fe+Ca) durante 2008-2009. Empleando modelos basados en ecuaciones estructurales se encontró que el carbono orgánico se relacionó positivamente con la riqueza y abundancia de HMF (λ>0.58) y fue variable en su relación con HSP-Fe y HSP-(Fe+Ca). Las relaciones del fósforo disponible, pH y las fracciones de macro-agregados fueron altamente variables. El IMPC se relacionó negativamente con HSP-Fe (λ≤-0.21) en cafetales colombianos. Se discuten las interacciones para cada conjunto de variables (químicas, estabilidad de macro-agregados y de manejo de plantación) y se explican las relaciones resultantes. Las relaciones de cada variable son inseparables del contexto edáfico y geográfico, los cuales imprimen marcadas diferencias.