Crop Losses Associated with Grasshoppers in Relation to Economics of Crop Production>
Grasshopper population estimates from an annual grasshopper survey were interfaced with crop-yield estimates and weather information to provide a quantitative assessment of the impact of grasshoppers on Saskatchewan agriculture. Two multiple regression models were deve1oped to estimate yields of wheat, oats, and barley on an individual district basis during a 32-yr period (1943–74). One model included year, precipitation, and a heatprecipitation ratio; the other incorporated grasshoppers as an additional variable. The model including grasshoppers explained a higher proportion of the variance than the model without grasshoppers. Estimates of crop yield from the regression models were used to develop a model of yield loss caused by grasshoppers for each of the 3 crops.
The economic impact of grasshoppers on wheat production was evaluated by using estimated losses based on actual crop prices and indexed costs related to production and crop protection. Results showed that losses caused by grasshoppers were dynamic but small relative to dynamics of crop price and yield losses independent of grasshoppers. Economic losses caused by grasshoppers tend to occur when economic gains are otherwise depressed because of poor crop yields due to drought or low crop prices. In 1961, in spite of extensive measures taken to protect the crop from grasshopper depredation, loss in wheat production due to grasshoppers was estimated to have been $40 million, representing ca. 17% of the value received for wheat. Wheat yields in 1961 were 0.565 T /ha (8.4 bu/acre) compared to the 20-yr avg of 1.425 T /ha (21.2 bu/acre).
The avg probability of economic loss in Saskatchewan (all districts during 1943–74) was 0.48, 0.72, and 0.32 for wheat, oats, and barley, respectively, based on 1976 prices and costs, with the highest chance of loss occurring in the southwestern region of the province. Since a high probability exists both of having drought and high grasshopper populations in the southwestern region, it is wise to consider reducing small-grain production there and growing other crops instead.
Document Type: Research Article
Publication date: June 1, 1978
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Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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