Author
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Begna, Sultan |
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FIELDING, DENNIS |
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Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/2/2005 Publication Date: 12/20/2005 Citation: Begna, S.H., Fielding, D.J. 2005. Response of barley to grasshopper defoliation in Interior Alaska: dry matter and grain yield. Journal of Economic Entomology 98(6): 1969-1976 Interpretive Summary: Barley (Hordeum vulgare L.) is well adapted to subarctic Alaska growing conditions, but little is known about its response to grasshopper defoliation. A field experiment was conducted to study dry matter and grain yield in response to a combination of grasshopper defoliation and weeds in 2002 and 2003 near Delta Junction (630 55' N,1450 20' W), Alaska. Barley plants were exposed to a combination of 2 levels of weeds (present, absent) and 4 densities of grasshoppers (equivalent to 0, 25, 50, and 75 grasshoppers m-2). Plant growth and grain yield were much lower in 2003 than in 2002, probably due to thought conditions early in the growing season of 2003. Harvestable grain yield was significantly reduced at the medium and highest levels of grasshoppers in both years. Head clipping accounted for a greater portion of yield loss in 2003 than in 2002. Early season drought reduced yields primarily by fewer seeds per head, whereas grasshoppers reduced average seed weight, but not numbers of seeds. This research brought about a better understanding of the effects of different types of stresses on barley, and will lead to better predictions of the relative costs and benefits associated with crop protection efforts. Technical Abstract: Barley (Hordeum vulgare L.) is well adapted to subarctic Alaska growing conditions, but little is known about its response to grasshopper defoliation. A field experiment was conducted to study dry matter and grain yield in response to a combination of grasshopper defoliation and weeds in 2002 and 2003 near Delta Junction (630 55' N, 1450 20' W), Alaska. Barley plants at 3'd to 4'h leaf stage were exposed to a combination of 2 levels of weeds (present, absent) and 4 densities of grasshoppers (equivalent to 0, 25, 50, and 75 grasshoppers m-2) of 3'4 to 4'h instar Melanoplus sanguinipes F. Dry matter accumulation by the barley plants was determined at 3 times during the growing seasons: about 10 days after introduction of the grasshoppers, shortly after anthesis, and at maturity. Dry matter accumulation and grain yield were much lower in 2003 than in 2002, probably due to very low levels of soil moisture early in the growing season of 2003. Dry matter accumulation was reduced by the highest level of grasshopper density at all harvests in 2002 but only at the final harvest in 2003. Harvestable grain yield was significantly reduced at the medium and highest levels of grasshoppers in both years. Head clipping accounted for a greater portion of yield loss in 2003 than in 2002. The percent reduction in harvestable yield due to grasshoppers remained fairly constant between years (3 and 4 % for each 5 grasshoppers m-2 in 2002 and 2003, respectively) despite a large difference in overall yield. Examination of the yield components suggest that yields were reduced by the early-season drought in 2003 primarily through fewer seeds per head, whereas grasshoppers in both years reduced average seed weight, but not numbers of seeds. |
