Biological control of alfalfa blotch leafminer (Diptera: Agromyzidae) in Ontario: Status and ecology of parasitoids (Hymenoptera: Braconidae, Eulophidae) 20 years after introduction

George E Heimpel, Francois Meloche

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Abstract

Two European parasitoid species were released in Ontario during the late 1970's to control the alfalfa blotch leafminer, Agromyza frontella (Rondani)(Diptera: Agromyzidae). One of these, Dacnusa dryas (Nixon)(Hymenoptera: Braconidae), rapidly became established and the other, Chrysocharis liriomyzae (= C. punctifacies) (Delucchi) (Hymenoptera: Eulophidae) was never recovered in Ontario. In 1999, we found both D. dryas and C. liriomyzae parasitizing first-generation A. frontella in Ontario in 1999. The combined parasitism rate for both species as revealed by larval dissections was 97.5% by the end of the first A. frontella generation. Of the adult parasitoids reared, 86% were D. dryas and 14% were C. liriomyzae. Most parasitized larvae contained a single unencapsulated (i.e., healthy) larva, along with one or more encapsulated eggs. No larvae were encapsulated, but the overall egg encapsulation rate was 47%. By the end of the first A. frontella generation, 86% of parasitized hosts contained at least one unencapsulated parasitoid and could therefore produce an adult parasitoid, and 12% of parasitized hosts escaped parasitism by containing only encapsulated parasitoids. The sex ratio of D. dryas was even at emergence, but strongly female-biased in sweep samples from the field. Egg loads of D. dryas females were all greater than zero and as high in the field as our highest laboratory estimates, suggesting that egg availability does not limit fitness under the conditions that we observed in the field.

Original languageEnglish (US)
Pages (from-to)17-26
Number of pages10
JournalGreat Lakes Entomologist
Volume34
Issue number1
StatePublished - Mar 1 2001

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Agromyza frontella
Agromyzidae
leafminer
Eulophidae
Braconidae
alfalfa
biological control
Ontario
parasitoids
Hymenoptera
parasitoid
egg
ecology
larva
parasitism
larvae
Dacnusa
Chrysocharis
encapsulation
dissection

Cite this

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title = "Biological control of alfalfa blotch leafminer (Diptera: Agromyzidae) in Ontario: Status and ecology of parasitoids (Hymenoptera: Braconidae, Eulophidae) 20 years after introduction",
abstract = "Two European parasitoid species were released in Ontario during the late 1970's to control the alfalfa blotch leafminer, Agromyza frontella (Rondani)(Diptera: Agromyzidae). One of these, Dacnusa dryas (Nixon)(Hymenoptera: Braconidae), rapidly became established and the other, Chrysocharis liriomyzae (= C. punctifacies) (Delucchi) (Hymenoptera: Eulophidae) was never recovered in Ontario. In 1999, we found both D. dryas and C. liriomyzae parasitizing first-generation A. frontella in Ontario in 1999. The combined parasitism rate for both species as revealed by larval dissections was 97.5{\%} by the end of the first A. frontella generation. Of the adult parasitoids reared, 86{\%} were D. dryas and 14{\%} were C. liriomyzae. Most parasitized larvae contained a single unencapsulated (i.e., healthy) larva, along with one or more encapsulated eggs. No larvae were encapsulated, but the overall egg encapsulation rate was 47{\%}. By the end of the first A. frontella generation, 86{\%} of parasitized hosts contained at least one unencapsulated parasitoid and could therefore produce an adult parasitoid, and 12{\%} of parasitized hosts escaped parasitism by containing only encapsulated parasitoids. The sex ratio of D. dryas was even at emergence, but strongly female-biased in sweep samples from the field. Egg loads of D. dryas females were all greater than zero and as high in the field as our highest laboratory estimates, suggesting that egg availability does not limit fitness under the conditions that we observed in the field.",
author = "Heimpel, {George E} and Francois Meloche",
year = "2001",
month = "3",
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language = "English (US)",
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journal = "Great Lakes Entomologist",
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T1 - Biological control of alfalfa blotch leafminer (Diptera

T2 - Agromyzidae) in Ontario: Status and ecology of parasitoids (Hymenoptera: Braconidae, Eulophidae) 20 years after introduction

AU - Heimpel, George E

AU - Meloche, Francois

PY - 2001/3/1

Y1 - 2001/3/1

N2 - Two European parasitoid species were released in Ontario during the late 1970's to control the alfalfa blotch leafminer, Agromyza frontella (Rondani)(Diptera: Agromyzidae). One of these, Dacnusa dryas (Nixon)(Hymenoptera: Braconidae), rapidly became established and the other, Chrysocharis liriomyzae (= C. punctifacies) (Delucchi) (Hymenoptera: Eulophidae) was never recovered in Ontario. In 1999, we found both D. dryas and C. liriomyzae parasitizing first-generation A. frontella in Ontario in 1999. The combined parasitism rate for both species as revealed by larval dissections was 97.5% by the end of the first A. frontella generation. Of the adult parasitoids reared, 86% were D. dryas and 14% were C. liriomyzae. Most parasitized larvae contained a single unencapsulated (i.e., healthy) larva, along with one or more encapsulated eggs. No larvae were encapsulated, but the overall egg encapsulation rate was 47%. By the end of the first A. frontella generation, 86% of parasitized hosts contained at least one unencapsulated parasitoid and could therefore produce an adult parasitoid, and 12% of parasitized hosts escaped parasitism by containing only encapsulated parasitoids. The sex ratio of D. dryas was even at emergence, but strongly female-biased in sweep samples from the field. Egg loads of D. dryas females were all greater than zero and as high in the field as our highest laboratory estimates, suggesting that egg availability does not limit fitness under the conditions that we observed in the field.

AB - Two European parasitoid species were released in Ontario during the late 1970's to control the alfalfa blotch leafminer, Agromyza frontella (Rondani)(Diptera: Agromyzidae). One of these, Dacnusa dryas (Nixon)(Hymenoptera: Braconidae), rapidly became established and the other, Chrysocharis liriomyzae (= C. punctifacies) (Delucchi) (Hymenoptera: Eulophidae) was never recovered in Ontario. In 1999, we found both D. dryas and C. liriomyzae parasitizing first-generation A. frontella in Ontario in 1999. The combined parasitism rate for both species as revealed by larval dissections was 97.5% by the end of the first A. frontella generation. Of the adult parasitoids reared, 86% were D. dryas and 14% were C. liriomyzae. Most parasitized larvae contained a single unencapsulated (i.e., healthy) larva, along with one or more encapsulated eggs. No larvae were encapsulated, but the overall egg encapsulation rate was 47%. By the end of the first A. frontella generation, 86% of parasitized hosts contained at least one unencapsulated parasitoid and could therefore produce an adult parasitoid, and 12% of parasitized hosts escaped parasitism by containing only encapsulated parasitoids. The sex ratio of D. dryas was even at emergence, but strongly female-biased in sweep samples from the field. Egg loads of D. dryas females were all greater than zero and as high in the field as our highest laboratory estimates, suggesting that egg availability does not limit fitness under the conditions that we observed in the field.

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