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Title: DAMAGE POTENTIAL OF GRASSHOPPERS (ORTHOPTERA: ACRIDIDAE) ON EARLY GROWTH STAGES OF SMALL-GRAINS AND CANOLA UNDER SUBARCTIC CONDITIONS.

Author
item BEGNA, S - UNIVERSITY OF ALASKA
item FIELDING, DENNIS

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2003
Publication Date: 10/1/2003
Citation: Begna, S.H., Fielding, D.J. 2003. Damage potential of grasshoppers (Orthoptera: Acrididae) on early growth stages of small-grains and canola under subarctic conditions. Journal of Economic Entomology 96(4): 1193-1200

Interpretive Summary: Newly hatched grasshoppers frequently invade crops from field margins, damaging young plants. Whether it is economically worthwhile to control these grasshoppers depends, in part, on how much defoliation results from a given number of grasshoppers, and how that defoliation affects overall growth of the crop. A growth chamber study quantified damage to above- and below-ground plant parts for four crops [(barley, oats, wheat (Triticum aestivum L.), and canola (Brassica campestris L.). Cages were stocked with grasshoppers equivalent to densities of 0, 50, 100, and 150 hoppers m-2. The highest grasshopper density reduced leaf area in barley and oats by about 55%, and caused a significant reduction in dry weight of leaves, stems, and roots (41 to 72%). At the highest grasshopper density, above-ground portions of wheat and canola were completely destroyed. Length and surface area of roots of barley, oats, wheat, and canola were reduced by 21, 32, 50, and 90%, respectively, by the highest grasshopper density. The results suggest that wheat and canola are more susceptible than barley and oats. Densities 50 m-2 of young grasshoppers could cause significant damage in small-grain and oilseed crop production.

Technical Abstract: Small-grains, such as barley and oats, have been successfully grown under subarctic conditions but little is known about their response to herbivory by grasshoppers, especially during seedling stages. A growth chamber study quantified and characterized damage to above- and below-ground plant parts for four crops (barley, oats, wheat, and canola). Cages were placed on pots containing plants in 2nd to 3rd leaf stages and stocked with first-instar grasshoppers equivalent to densities of 0, 50, 100, and 150 hoppers m-2. The highest grasshopper density treatment reduced leaf area in barley and oats by about 55%, and caused a significant reduction in dry weight of leaves, stems, and roots (41 to 72%). At the highest grasshopper density, above-ground portions of wheat and canola were completely destroyed. Length and surface area of roots of barley, oats, wheat, and canola were reduced by 21, 32, 50, and 90%, respectively, by the highest grasshopper density. The results suggest that wheat and canola are more susceptible than barley and oats. Densities 50 m-2 of small grasshoppers could cause significant damage in small-grain and oilseed crop production.