AUTHOR=McPike Sarah M. , Evenden Maya L. 

TITLE=Host Plant Volatile Lures Attract Apanteles polychrosidis (Hymenoptera: Braconidae) to Ash Trees Infested With Caloptilia fraxinella (Lepidoptera: Gracillariidae)

JOURNAL=Frontiers in Ecology and Evolution

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2021.701954

DOI=10.3389/fevo.2021.701954

ISSN=2296-701X

ABSTRACT=<p><italic>Caloptilia fraxinella</italic> Ely (Lepidoptera: Gracillariidae), the ash leaf-cone roller, is an aesthetic pest of horticultural ash trees (Oleaceae, Genus <italic>Fraxinus</italic>) in prairie communities across Canada. Because pesticide use is undesirable in urban centers, biological control of <italic>C. fraxinella</italic> is a preferred approach. The native parasitoid wasp, <italic>Apanteles polychrosidis</italic> Vierek (Hymenoptera: Braconidae), has shifted hosts and is the primary parasitoid of <italic>C. fraxinella</italic> in Edmonton, Alberta, Canada, and has potential as a biological control agent. Here, in an effort to increase parasitism of <italic>C. fraxinella</italic>, lures releasing methyl salicylate (MeSA) and two green leaf volatiles (GLVs), [(<italic>Z</italic>)-3-hexenol, and (<italic>Z</italic>)-3-hexenyl-acetate], at both low and high release rates, were tested to enhance attraction and retention of <italic>A. polychrosidis</italic> in infested ash trees. Attraction of <italic>A. polychrosidis</italic> to baited trees was measured by capture on yellow sticky cards positioned in the tree canopy, and wasp activity was assessed by the parasitism rate of <italic>C. fraxinella</italic>. More male and female <italic>A. polychrosidis</italic> were captured on yellow sticky traps positioned in trees baited with the low dose of both MeSA + GLVs than to unbaited, infested ash trees. The increased attraction of wasps did not correlate with an increase in parasitism of <italic>C. fraxinella</italic>. The high release rate lures did not enhance attraction of <italic>A. polychrosidis</italic> to infested ash trees. Parasitism rate, however, was negatively correlated with host density in both field experiments. There was no evidence of close-range attraction to lures in an olfactometer assay. Synthetic HIPVs attract <italic>A. polychrosidis</italic> to ash trees infested with <italic>C. fraxinella</italic>, but the effect of wasp attraction on parasitism rate requires further research if HIPVs are to be used to enhance biological control in this system.</p>