Predominant crops (corn, bean and alfalfa) in the Puebla-Tlaxcala Valley are routinely attacked by the grasshopper Sphenarium purpurascens (Orthoptera: Pyrgomophidae). The traditional method for managing this pest in Mexico has been the application of organophosphorus insecticides such as malathion. Inhabitants from Central Mexico also capture the grasshoppers for sale as food. In this study, we compared the capture of grasshoppers for human consumption to the conventional application of insecticides as a pest management strategy. The number of oothecae (egg pod), eggs, eggs per ootheca and the reproductive rate (Ro) were estimated over 2 years of the study. Counts were made on the edge and inner part of nine alfalfa plots. Egg density was found to be significantly affected by control tactic, with control > manual harvest > insecticide application. Egg density at the edge of farming plots was 14.9 times higher than within a plot. Ros ranged from 1.74 to 4.88 in the control, from 0.21 to 0.98 in the plots under manual harvest and from 0.38 to 0.77 in the plots under insecticide application. Similar results were found comparing oothecae densities. A mean of 39.5 eggs/ootheca was found, which constitutes the highest recorded value for this species. This research shows that manual harvest reduces the density of S. purpurascens and suggests that implementation of this mechanical method of control may be substituted for chemical control. Mechanical control provides general advantages: (1) a second profitable product for the human community
(2) savings realized from reduced cost of insecticides
and (3) reduced risk of soil and water contamination by insecticides. We propose that the manual harvest of insects is a practical method of pest control, which could be extensively applied in other crop systems in the world. (C) 2007 Elsevier Ltd. All rights reserved.
