Parasitism of lygus and alfalfa plant bugs by Peristenus wasps in southern Alberta, Canada


Carcamo, H.A, S. Daniels, R. Branst. 2021. Parasitism of lygus and alfalfa plant bugs by Peristenus wasps in southern Alberta, Canada. Abstract of the 2021 Entomological Society of Canada Conference. 15-18 November 2021. Online meeting.

Résumé en langage clair

Parasitoids are parasites that kill their hosts. For lygus bugs, a group of small wasps called Peristenus attack and kill small juveniles, particularly in weedy alfalfa and sainfoin. We found very high levels of attack but restricted to a very short time period. Proper timing of insecticides may help conserve these native parasitoids in crops. Also, there is room for another parasitoid with a broader activity period.


Mirid plant bugs of the genus Lygus and Adelphocoris (alfalfa plant bug) are common pests of seed alfalfa and other crops. At least 3 species of native Peristenus wasps (Braconidae) attack this plant bug complex, but the local parasitoid-host relationships and timing of parasitism are poorly known. Our objective in this study was to rear parasitoids from the two generations of these plant bugs and to quantify levels of parasitism in the spring and summer in alfalfa and sainfoin. Alfalfa plant bugs had very high levels of parasitism in late spring/early summer and higher than those observed for lygus during the same period. High levels of parasitism (over 50%) were restricted to a cohort of nymphs indicating that wasps had a short successful attack period in late spring or early summer (mid to late June in 2021). Levels of parasitism were much lower for lygus later in the season and absent from alfalfa plant bugs. This study will be expanded to other crops in the future with the aim to collect more baseline data in consideration of neo-classical biological control of lygus bugs with the multivoltine, P. digoneutis.

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