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Damage potential of grasshoppers (Orthoptera: Acrididae) on early growth stages of small-grains and canola under subarctic conditions

Begna, S.H., Fielding D.J.
Journal of economic entomology 2003 v.96 no.4 pp. 1193
Melanoplus sanguinipes, Hordeum vulgare, Avena sativa, Triticum aestivum, Brassica napus var. napus, barley, oats, wheat, canola, population density, crop damage, developmental stages, aerial parts, underground parts, plant growth, dry matter accumulation, plant morphology, carbon nitrogen ratio, grasshoppers, insect pests, cold zones
We characterized the type and extent of grasshopper injury to above- and below-ground plant parts for four crops, i.e. barley (Hordeum vulgare), oats (Avena sativa), wheat (Triticum aestivum), and canola [turnip rape] (Brassica campestris [B. campestris var. oleifera]), commonly grown, or with potential to grow, in central Alaska, USA. Cages were placed on 48 pots containing plants in second to third leaf stages and stocked with 0, 2, 4, and 6 first-instar Melanoplus sanguinipes pot-1. Plants were harvested 22 days after planting. Stem growth of barley and oats was not affected except at the highest grasshopper treatment. In rape, stem biomass was reduced at the medium and high grasshopper treatments, when most of the leaves had been consumed. The highest grasshopper treatment reduced leaf area in barley and oats by ~55%, and caused a significant reduction in dry weight of leaves, stems, and roots (41-72%). Wheat and canola plants were smaller than barley and oats across all treatments and, at the highest grasshopper density, above-ground portions of wheat and canola were completely destroyed. Length and surface area of roots of barley and oats were reduced by 20-28% again at the highest grasshopper density, whereas the reduction for wheat and canola ranged from 50 to 90%. There was little or no difference among all grasshopper densities for C:N ratio in leaf and stem tissues of all crops. The results suggest that wheat and canola are more susceptible than barley and oats and that densities ≥2 pot-1 (~≥50 m-2) of even very small grasshoppers could cause significant damage in small-grain and oilseed crop production.