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METZNERIA PAUCIPUNCTELLA ZELLER (LEPIDOPTERA: GELECHIIDAE), A MOTH INTRODUCED AGAINST SPOTTED KNAPWEED: ITS FEEDING STRATEGY AND IMPACT ON TWO INTRODUCED UROPHORA SPP. (DIPTERA: TEPHRITIDAE)1

Published online by Cambridge University Press:  31 May 2012

J.M. Story ,
K.W. Boggs ,
W.R. Good ,
P. Harris  and
R.M. Nowierski
J.M. Story
Affiliation:
Montana Agricultural Experiment Station, Western Agricultural Research Center, 580 Quast Ln., Corvallis, Montana, USA 59828
K.W. Boggs
Affiliation:
Montana Agricultural Experiment Station, Western Agricultural Research Center, 580 Quast Ln., Corvallis, Montana, USA 59828
W.R. Good
Affiliation:
Montana Agricultural Experiment Station, Western Agricultural Research Center, 580 Quast Ln., Corvallis, Montana, USA 59828
P. Harris
Affiliation:
Montana Agricultural Experiment Station, Western Agricultural Research Center, 580 Quast Ln., Corvallis, Montana, USA 59828
R.M. Nowierski
Affiliation:
Montana Agricultural Experiment Station, Western Agricultural Research Center, 580 Quast Ln., Corvallis, Montana, USA 59828
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Abstract

Metzneria paucipunctella Zeller is a seed head moth introduced for biological control of spotted knapweed, Centaurea maculosa Lamarck, in the Pacific Northwest. A cage study was conducted in Montana in 1987 and 1988 to assess the feeding strategy of the M. paucipunctella larva and its impact on two seed head flies, Urophora spp., also introduced on spotted knapweed. Each moth larva destroyed an average of 8.13 knapweed seeds. Most of the seeds were destroyed prior to seed dispersal in early September but the remaining seeds were attacked in the spring of the following year. Each larva tied an average of 7.0 seeds with silk webbing which allowed for feeding long after normal seed dispersal. Seed survival in cages containing both the moth and the two fly species (4.71 seeds per head) was significantly less than in fly-only cages (9.75 seeds per head). The moth larvae caused extensive mortality to the two Urophora species, especially during the spring months. Moth-caused mortality to U. affinis larvae increased from 19% during June through October to 67% in May of the following year. Mortality to U. quadrifasciata also occurred but did not increase significantly in the spring. Data from 10 field sites showed very little association between M. paucipunctella and the two Urophora species which suggests that the unnatural conditions associated with the cages did not increase the incidence of joint moth and fly attack to individual seed heads. The moth is a valuable biocontrol agent as it is contributing significantly to the overall consumer pressure on spotted knapweed seed heads.

Résumé

Metzneria paucipunctella Zeller, papillon vivant dans les capitules, a été introduit pour assurer le contrôle biologique de la Centaurée maculée Centaurea maculosa Lamarck dans le nord-ouest américain. L’installation de cages en 1987 et 1988 a permis d’évaluer la stratégie alimentaire des larves de M. paucipunctella et d’estimer leur impact sur deux mouches parasites des capitules, Urophora spp., également introduites pour le contrôle de la centaurée. Chaque chenille a détruit en moyenne 8,13 graines de la centaurée. La plupart des graines ont été détruites avant la dispersion au début de septembre, mais d’autres graines ont été attaquées au cours du printemps de l’année suivante. Chaque larve attachait en moyenne 7,0 graines dans une toile de soie, ce qui lui allouait une quantité de nourriture suffisante pour subsister longtemps après la période normale de dispersion des graines. La survie des graines dans les cages contenant à la fois le papillon et les deux espèces de mouches (4,71 graines per capitule) était significativement moins élevée que celle des graines dans les cages ne contenant que des mouches (9,75 graines per capitule). Les larves du papillon ont entraîné une forte mortalité chez les deux espèces d’Urophora, surtout au cours des mois de printemps. La mortalité des larves d’U. affinis attribuable au papillon, évaluée à 19% entre juin et octobre, est passée à 67% en mai de l’année suivante. Le papillon a aussi causé de la mortalité chez U. quadrifasciata, mais cette mortalité n’a pas augmenté significativement au printemps. Les données recueillies en 10 points d’échantillonnage ont révélé qu’il y avait peu de lien entre M. paucipunctella et les deux espèces d’Urophora, ce qui indique que les conditions artificielles créées par les cages n’ont pas augmenté le nombre d’attaques conjointes du papillon et des mouches par capitule. Le papillon est un agent de contrôle biologique efficace puisqu’il contribue de façon inportante à la pression de consommation générale opérée sur les capitules de la Centaurée maculée.

[Traduit par la rédaction]

Type
Articles
Information
The Canadian Entomologist , Volume 123 , Issue 5 , October 1991 , pp. 1001 - 1007
Copyright
Copyright © Entomological Society of Canada 1991

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