Abstract

MARIOTTINI, Y; DE WYSIECKI, M.L  and  LANGE, C.E. Pérdida de forraje ocasionada por diferentes densidades de Dichroplusmaculipennis (Acrididae: Melanoplinae) en una pastura de Festuca arundinacea Schreb. RIA. Rev. investig. agropecu. [online]. 2018, vol.44, n.1, pp.92-100. ISSN 1669-2314.

The grasshopper Dichroplus maculipennis is considered one of the most characteristic and damaging species of Argentina, mainly in areas of Pampas and Patagonia regions. In outbreak years, this species causes serious damage to grasslands as well as to implanted pastures and various crops. Considering this, the main goal of this study was to estimate the loss of forage caused by different densities of D. maculipennis in adulthood on a pasture of forage value as Festuca arundinacea, under field conditions. The experience was conducted in a field of Tandil County, during January 2016. Adult individuals of D. maculipennis were placed in cages in a sex ratio 1:1. Forage loss caused by three different densities was estimated with 8 ind/m², 16 ind/ m² and 32 ind/m². Three replicates were performed for each assayed density; also three cages were established without grasshoppers as control. The harvested biomass at the end of the experiment in control cages was 337,8 ± 7,5 g/m², in cages with a density of 8 ind/m² was 262,9 ± 11,8 g/m², those with 16 ind / m² was 227,6 ± 6 g / m² and in cages with 32 ind/m² was 154,6 ± 9,9 g/m². The three densities caused a significant decrease in the biomass of F. arundinacea respect to the control (p <0,0001). Plant biomass harvested from cages with the highest density of grasshoppers was significantly lower than that obtained from cages with the other two densities (p <0,05). One insect per day caused a forage loss of 0,02 ± 0,236 g/m², on average. From the results, it can be inferred that a density of 8 ind/m² would produce a forage loss of 749 kg/ha, 16 ind/m² would produce a forage loss of 1107,4 kg/ha, and with 32 ind/m² the loss would be 1873 kg/ha. The latter would cause a decrease of 55% of the biomass of pasture in one month.

Keywords : Grasshopper pest; Melanoplinae; Forage loss; Pastures; Pampas region.

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