Environmental Entomology (1988) 17, 337-343

D.G. Harcourt, J.C. Guppy and F. Meloche (1988)
Population dynamics of the alfalfa blotch leafminer, Agromyza frontella (Diptera: Agromyzidae), in eastern Ontario: Impact of the exotic parasite Dacnusa dryas (Hymenoptera: Braconidae)
Environmental Entomology 17 (2), 337-343
Abstract: Colonization of eastern Ontario by the alfalfa blotch leafminer, Agromyza frontella (Rondani), during the mid-1970s was characterized by a rapid population build-up followed by an equally rapid decline to more tolerable levels. This decline occurred because of maggot mortality within the leaf mines from a combination of intrinsic and extrinsic factors. A gradation to still lower levels resulted from attacks of the introduced exotic parasite Dacnusa dryas (Nixon). Thirty host life tables were derived from population and mortality data collected after establishment of the parasite and were compared to similar data for the period of colonization. Analysis of population change showed that D. dryas has become the principal agent that determines population trends and that maggot mortality is no longer the key factor, primarily because of a diminished level of larval intraspecific competition. D. dryas was released as a single species introduction, and within 3 yr of its establishment, it had caused a 50-fold reduction in numbers of its host. The success of the parasite is attributed to a high dispersal capability, a high degree of host specificity,. excellent synchronization with its host, and a rapid rate of acclimation. Since the establishment of the parasite in eastern Ontario, generation survival of the leafminer has fallen by more than two-thirds, and populations have collapsed to subeconomic levels.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): François Meloche

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
population dynamics/ epidemiology
Research topic(s) for beneficials or antagonists:
population dynamics/epizootiology
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Agromyza frontella	Alfalfa/lucerne (Medicago sativa)	Canada (east)
Dacnusa dryas (parasitoid)	Agromyza frontella	Alfalfa/lucerne (Medicago sativa)	Canada (east)