Abundance, distribution, and associated forage losses of pest grasshoppers (Orthoptera: Acrididae) in the Argentine Pampas

The goal of this study was to assess the status of Dichroplus elongatus and Borellia bruneri as actual agricultural pests in the Argentine Pampas by determining their abundance, distribution, and associated forage loss. The study was conducted in Laprida and Tandil, two counties in Buenos Aires province. In each county 20 sampling sites were established and monitored from 2012 to 2018. B. bruneri was more abundant and with a wider distribution in Laprida (91.4% of the sites) than in Tandil (42.1% of the sites) while D. elongatus abundance was significantly higher from 2012 to 2016 in Tandil than in Laprida and its distribution was wide in Laprida (75% of the sites) and very wide in Tandil (77.14%). Under field-cage conditions forage loss caused at three different densities (8, 16, and 32 ind/m2) of D. elongatus and B. bruneri adults on a pasture of Festuca arundinacea was estimated. Forage loss caused by D. elongatus was significantly higher than that caused by B. bruneri. Dichroplus elongatus caused a significant decrease in biomass at the three densities respect to the control, while B. bruneri only caused a significant decrease at the highest density. Our study suggests that although the gomphocerine B. bruneri is an abundant and widely-distributed species capable of doing some damage in the grasslands of the southern Pampas, it is comparatively much less harmful than the melanopline D. elongatus