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Alfalfa

The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform

Leon G. Higley – 1st expert on this subject based on the ideXlab platform

  • Yield Responses of Alfalfa to Simulated Alfalfa Weevil Injury and Development of Economic Injury Levels
    Agronomy Journal, 1993
    Co-Authors: Robert K. D. Peterson, Stephen D. Danielson, Leon G. Higley

    Abstract:

    Although the Alfalfa weevil Hypera postica (Gyllenhal)] is an important Alfalfa (Medicago sativa L.) pest, relatively little is known about how defoliation at specific plant developmental stages affects yield. This study was conducted to characterize yield responses of Alfalfa to simulated Alfalfa weevil injury when injury was initiated at the early hud stage of the first growth cycle and to develop economic injury levels for the Alfalfa weevil. The study was conducted on a silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in a 3.6-ha Alfalfa (cv. Haymaker) field near Walton, NE […]

  • Photosynthetic Responses of Alfalfa to Actual and Simulated Alfalfa Weevil (Coleoptera: Curculionidae) Injury
    Environmental Entomology, 1992
    Co-Authors: Robert K. D. Peterson, Stephen D. Danielson, Leon G. Higley

    Abstract:

    The Alfalfa weevil, Hypera postica (Gyllenhal), is the most important leafmass consumer of Alfalfa, Medicago sativa L. However, little is known about how insect defoliation injury affects photosynthetic responses of Alfalfa. Studies were conducted in 1990 and 1991 to characterize the gas exchange responses of Alfalfa to simulated and actual Alfalfa weevil larval injury. Gas exchange responses were observed for two levels of plant organization: (1) the remaining tissue of injured leaves and (2) the remaining leaves of defoliated plants. Transpiration and stomatal conductance rates for leaves with actual and simulated Alfalfa weevil injury were greater than for leaves without defoliation injury. However, photosynthetic rates of leaves with simulated and actual Alfalfa weevil injury were not significantly different from each other or from leaves without defoliation injury. Consequently, both simulated and actual Alfalfa weevil injury did not seem to affect the photosynthetic apparatus of the remaining leaf tissue. Therefore, the principal effect of Alfalfa weevil defoliation injury on photosynthetic responses of Alfalfa was to reduce the amount of photosynthesizing leaf tissue, but not photosynthetic rates. Moreover, simulated Alfalfa weevil injury techniques produced photosynthetic responses that were not significantly different from actual Alfalfa weevil injury. Defoliated plants responded to simulated Alfalfa weevil injury by altering the normal senescence pattern of the remaining leaves. In particular, leaves of defoliated plants maintained higher photosynthetic rates than corresponding leaves of control plants, which showed normal senescence patterns of decreasing photosynthetic rates. As defoliation injury increased in magnitude, leaf senescence of the remaining leaves proceeded at a progressively slower rate. Delayed leaf senescence seems to be a plant compensatory response to Alfalfa weevil defoliation injury.

Robert K. D. Peterson – 2nd expert on this subject based on the ideXlab platform

  • Yield Responses of Alfalfa to Simulated Alfalfa Weevil Injury and Development of Economic Injury Levels
    Agronomy Journal, 1993
    Co-Authors: Robert K. D. Peterson, Stephen D. Danielson, Leon G. Higley

    Abstract:

    Although the Alfalfa weevil Hypera postica (Gyllenhal)] is an important Alfalfa (Medicago sativa L.) pest, relatively little is known about how defoliation at specific plant developmental stages affects yield. This study was conducted to characterize yield responses of Alfalfa to simulated Alfalfa weevil injury when injury was initiated at the early hud stage of the first growth cycle and to develop economic injury levels for the Alfalfa weevil. The study was conducted on a silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in a 3.6-ha Alfalfa (cv. Haymaker) field near Walton, NE […]

  • Photosynthetic Responses of Alfalfa to Actual and Simulated Alfalfa Weevil (Coleoptera: Curculionidae) Injury
    Environmental Entomology, 1992
    Co-Authors: Robert K. D. Peterson, Stephen D. Danielson, Leon G. Higley

    Abstract:

    The Alfalfa weevil, Hypera postica (Gyllenhal), is the most important leafmass consumer of Alfalfa, Medicago sativa L. However, little is known about how insect defoliation injury affects photosynthetic responses of Alfalfa. Studies were conducted in 1990 and 1991 to characterize the gas exchange responses of Alfalfa to simulated and actual Alfalfa weevil larval injury. Gas exchange responses were observed for two levels of plant organization: (1) the remaining tissue of injured leaves and (2) the remaining leaves of defoliated plants. Transpiration and stomatal conductance rates for leaves with actual and simulated Alfalfa weevil injury were greater than for leaves without defoliation injury. However, photosynthetic rates of leaves with simulated and actual Alfalfa weevil injury were not significantly different from each other or from leaves without defoliation injury. Consequently, both simulated and actual Alfalfa weevil injury did not seem to affect the photosynthetic apparatus of the remaining leaf tissue. Therefore, the principal effect of Alfalfa weevil defoliation injury on photosynthetic responses of Alfalfa was to reduce the amount of photosynthesizing leaf tissue, but not photosynthetic rates. Moreover, simulated Alfalfa weevil injury techniques produced photosynthetic responses that were not significantly different from actual Alfalfa weevil injury. Defoliated plants responded to simulated Alfalfa weevil injury by altering the normal senescence pattern of the remaining leaves. In particular, leaves of defoliated plants maintained higher photosynthetic rates than corresponding leaves of control plants, which showed normal senescence patterns of decreasing photosynthetic rates. As defoliation injury increased in magnitude, leaf senescence of the remaining leaves proceeded at a progressively slower rate. Delayed leaf senescence seems to be a plant compensatory response to Alfalfa weevil defoliation injury.

S. S. Quisenberry – 3rd expert on this subject based on the ideXlab platform

  • Identification of Alfalfa resistance to the threecornered Alfalfa hopper (Homoptera : Membracidae)
    Journal of Economic Entomology, 1992
    Co-Authors: D. J. Moellenbeck, S. S. Quisenberry

    Abstract:

    Six Alfalfa, Medicago sativa L., cultivars were screened in the greenhouse for antixenosis and antibiosis to the threecornered Alfalfa hopper, Spissistilus festinus (Say). The cultivars ‘Zia’ and ‘Cimarron VR’ showed antixenotic properties by harboring lower adult populations and exhibiting less girdle damage. ‘Cimarron’ was the most preferred cultivar based upon increased girdle damage and larger adult populations. In the antibiosis test, significant variation among the cultivars was found for adult male weights but not female weights, indicating sex-based differences in threecornered Alfalfa hopper susceptiblity to antibiotic factors. ‘Dona Ana’ exhibited antibiosis by decreasing male adult threecornered Alfalfa hopper weights; however, nymphal duration and female weights were not affected. Nymphal duration was significantly shorter on ‘Zia’ compared with ‘Florida 77’. Results show that variation in Alfalfa susceptibility to the threecornered Alfalfa hopper does exist, and further development of resistance may increase the importance of host-plant resistance in the management of this Alfalfa pest.

  • Population Dynamics and Seasonal Biology of the Alfalfa Weevil (Coleoptera: Curculionidae) on Alfalfa in Louisiana
    Environmental Entomology, 1990
    Co-Authors: Fred Whitford, S. S. Quisenberry

    Abstract:

    The biology of the Alfalfa weevil, Hypera postica (Gyllenhal), was studied in Louisiana during 1986 to 1988 on Alfalfa, Medicago sativa (L.). Post-estivation migration of adults in the fall occurs during late November and early December. Fall oviposition during December and January resulted in 58 to 81% of Alfalfa stems with egg clusters. Egg viability of eggs laid in the fall was estimated at 75%. Alfalfa weevil egg clusters contained an average of 10.9 (1986–1987) to 13.3 (1987–1988) eggs per cluster. The position of egg clusters in the Alfalfa canopy, relative to the base of the stem, indicated that 95 and 50% of all clusters were below 40 and 18 cm, respectively. An ovipositional preference was found with eggs generally laid between the upper 30% and lower 80% regions of the Alfalfa stem. Alfalfa weevil larvae were first detected in February. Egg eclosion in 1987 was highly synchronized as indicated by larval counts increasing from 4 to 90 per sweep between 3 and 10 February. In 1988, larval emergence gradually increased from 4 February (≦10/sweep) to 3 March (60/sweep). Head capsule widths were 0.15, 0.28, 0.42, and 0.55 mm for first, second, third, and fourth instars, respectively. Corresponding body lengths were 1.4, 2.8, 4.6, and 6.6 mm for first, second, third, and fourth instars, respectively. The marked decline of Alfalfa weevils in April is presumably indicative of adult migration from Alfalfa to summer estivation sites. Degree-day accumulations are used to describe and predict spring hatch of the Alfalfa weevil in Louisiana.