ABSTRACT: We assessed the damage produced by invertebrate herbivores per leaf lamina and per m2 of populations floating-leaf macrophytes of Neotropical wetlands in the growth and decay periods, and assessed if the damage produced by the herbivores should be taken into account in the estimations of plant biomass of these macrophytes or not. The biomass removed per lamina and per m2 was higher during the growth period than in decay period in Nymphoides indica and Hydrocleys nymphoides, while Nymphaea prolifera had low values of herbivory in growth period. During decay period this plant is only present as vegetative propagules. According to the values of biomass removed per m2 of N. indica, underestimation up to 17.69% should be produced in cases that herbivory do not should be taking account to evaluate these plant parameters on this macrophyte. Therefore, for the study of biomass and productivity in the study area, we suggest the use of corrected lamina biomass after estimating the biomass removed by herbivores on N. indica. The values of damage in N. indica emphasize the importance of this macrophyte as a food resource for invertebrate herbivores in the trophic networks of the Neotropical wetlands.

Abstract: Eichhornia crassipes and Eichhornia azurea are common invasive aquatic plants in Neotropical wetlands. These plants share species for their biological control, such as curculionoids of the genus Neochetina and the acridium Cornops aquaticum. In this study the herbivory of these specific insects was analyzed in leaves of E. azurea and E. crassipes, in period of growth and decay of plant populations; likewise, the herbivory of C. aquaticum was compared in both species of plants. Sampling was taken in 2 wetlands in the Argentine northeast, between January and February 2006 (growth period) and August 2006 (period of decay). At each sampling date, leaf samples of E. azurea and E. crassipes were collected. The herbivory was measured as the damaged leaf area and percentage of the leaf area damaged by herbivores. The herbivory was higher in growth period than in the decay in the 2 host species. The herbivory of C. aquaticum in the decay period was 0.34% in E. azurea and 0.44% in E. crassipes; in the growing period the damage caused by this acridium was higher in E. azurea (16.19%) than in E. crassipes (6.92%). During the decay period, only in E. crassipes, the herbivory by C. aquaticum was lower than that of the Neochetina species. The effectiveness of the herbivory varied between periods of population growth of the plants. The results show the importance of considering the combined action of these herbivores in the biological control of these aquatic plants.

Resumen: Eichhornia crassipes y Eichhornia azurea son plantas acuáticas invasivas comunes en humedales del neotrópico. Estas plantas comparten especies para su control biológico, como curculionoideos del género Neochetina y el acridio Cornops aquaticum. En este trabajo se analizó la herbivoría de estos insectos específicos en hojas de E. azurea y E. crassipes, en periodo de crecimiento y decaimiento de las poblaciones de plantas; asimismo, se comparó la herbivoría de C. aquaticum en ambas especies de plantas. Los muestreos se realizaron en 2 humedales del noreste argentino, entre enero y febrero de 2006 (periodo de crecimiento) y agosto de 2006 (periodo de decaimiento). En cada fecha de muestreo, se recolectaron muestras de hojas de E. azurea y E. crassipes. La herbivoría se midió como el área foliar dañada y el porcentaje del área foliar dañada por herbívoros. La herbivoría fue mayor en periodo de crecimiento que en el decaimiento en las 2 especies de hospederas. La herbivoría de C. aquaticum en el periodo de decaimiento fue del 0.34% en E. azurea y del 0.44% en E. crassipes; en el periodo de crecimiento el daño producido por este acridio fue mayor en E. azurea (16.19%) que en E. crassipes (6.92%). Durante el periodo de decaimiento, solo en E. crassipes la herbivoría por C. aquaticum fue menor que la de las especies de Neochetina. La efectividad de la herbivoría varió entre periodos de crecimiento poblacional de las plantas. Los resultados muestran la importancia de considerar la acción combinada de estos herbívoros en el control biológico de estas plantas acuáticas.