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Titre :
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Impact of Bemisia whiteflies (Homoptera : Aleyrodidae) on alfalfa growth, forage yield, and quality
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Auteurs :
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J. Palumbo ;
N. Toscano ;
M. Blua ;
H. Yoshida
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Type de document :
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article/chapitre/communication
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Année de publication :
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2000
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Format :
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1688-1694
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Langues:
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= Anglais
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Mots-clés:
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Bemisia argentifolii
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Bemisia tabaci
;
forage hay
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relative growth rate
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yield
;
quality
;
Action sur la plante
;
Croissance
;
Perte de rendement
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Medicago sativa
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Leguminoseae
;
Homopterae
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Résumé :
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A 3-yr project was initiated in 1993 to examine the effects of insecticides and sustained whitefly, Bemisia argentifolii Bellows & Perring [aka. B. tabaci Gennadius (Strain B)], feeding on alfalfa plant growth and vigor in greenhouse cage studies, and to determine the impact of natural Bemisia whitefly populations on alfalfa forage yields and duality in a large-plot field experiment. Alfalfa plant growth and vigor after exposure to imidacloprid and a mixture of fenpropathrin and acephate insecticides did not differ from untreated plants in the greenhouse. Consequently, foliar and soil applied insecticides were used to manipulate whitefly densities an alfalfa plants to measure whitefly feeding effects on plant growth and forage Field. Heavy whitefly densities on untreated alfalfa plants in the greenhouse resulted in significant reductions in relative growth rates and net assimilation rates as compared with imidacloprid-treated plants that were maintained relatively whitefly-free. Reductions in alfalfa plant growth measured between infested and treated plants were proportional to whitefly densities. Field plot results derived from three crop seasons were relatively consistent with our greenhouse trials. Both experimental approaches clearly showed that alfalfa plants exposed to high densities of whitefly immatures and adults grew at a significantly slower rate and produced less foliage. As a result of reduced growth rates. alfalfa maturity in the naturally infested plots was estimated to be approximate to7-10 d behind managed plots. Delays in maturity resulted in significant reductions in forage yields of 13-18% during August-September harvests when whitefly populations reached peak abundance. Whitefly feeding stresses also effected hay quality through the reduction of crude protein content and contamination of foliage with honeydew and sooty mold. The status of the Bemisia whiteflies as an economic pest to alfalfa is clearly evident from these studies, but the damage potential of whiteflies in the southwestern United Slates appears to be restricted to one or two harvest periods during the summer coinciding with peak adult populations and their dispersal from alternate host crops.
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Source :
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Journal of Economic Entomology - 0022-0493, vol. 93, n° 6
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