Author
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Begna, Sultan |
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Fielding, Dennis |
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Submitted to: Canadian Journal of Plant Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/6/2007 Publication Date: 1/20/2008 Citation: Begna, S.H., Fielding, D.J. 2008. Growth and yield of barley in relation to grasshopper feeding damage. Canadian Journal of Plant Science. 88:219-227. Interpretive Summary: Grasshoppers are common pests of barley in Alaska and cause substantial crop loss during outbreaks, but we do not know how much damage results in how much yield loss, or whether the cost of control measures are returned in crop savings. We examined the response of barley plants to 4 levels of grasshopper damage at 3 intervals in the plants' growth. Grasshoppers reduced total above-ground biomass, root biomass, and grain yield in roughly equal proportions. Photosynthetic rates (per leaf area) were not affected by grasshopper feeding. Final yield was reduced by 2.3% for every five grasshoppers per meter. Most of the yield loss was accounted for by reduced seed weights, rather than fewer seeds, but protein per seed remained nearly constant Technical Abstract: Grasshoppers are common pests of barley (Hordeum vulgare L.) in subarctic Alaska and cause substantial crop loss during outbreaks. However, there is little information about the growth response of barley to herbivory by grasshoppers. In two growth chamber experiments, we studied the effect of 4 densities (0, 1, 2, and 3 pot-1, equivalent to 0, 25, 50 and 75 grasshoppers m-2) of grasshoppers (Melanoplus sanguinipes F.) on the above-and below-ground growth of barley (8 plants pot-1). Plants were exposed to grasshoppers beginning in the 3rd to 4th leaf stage (experiment 1) and in 1st to 2nd leaf stage (experiment 2). Plants were harvested and growth variables were measured at 3 intervals. As density increased, values of most growth variables decreased. Generally, the reduction in above-ground dry matter (pooled over harvests), at the highest grasshoppers density was 29% and 47% for Exp.1 and Exp.2, respectively. Effects of grasshoppers on below-ground growth (dry matter and surface area of roots) was less consistent than on above-ground variables, however, at the highest grasshopper density in exp. 2, dry matter and surface area of roots were reduced by about 40-53%. Grain yield (pooled over experiments) decreased by 19 and 36% for grasshopper densities of 2 and 3 pot-1, respectively. Most of the yield loss was accounted for reduced seed weights, but protein content seed-1 remained nearly constant. The proportion of total above-ground dry matter represented in harvested grain and shoot:root ratios were not affected by grasshopper feed |
