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

Caloptilia fraxinella Ely (Lepidoptera: Gracillariidae), the ash leaf-cone roller, is an aesthetic pest of horticultural ash trees (Oleaceae, Genus Fraxinus) in prairie communities across Canada. Because pesticide use is undesirable in urban centers, biological control of C. fraxinella is a preferred approach. The native parasitoid wasp, Apanteles polychrosidis Vierek (Hymenoptera: Braconidae), has shifted hosts and is the primary parasitoid of C. fraxinella in Edmonton, Alberta, Canada, and has potential as a biological control agent. Here, in an effort to increase parasitism of C. fraxinella, lures releasing methyl salicylate (MeSA) and two green leaf volatiles (GLVs), [(Z)-3-hexenol, and (Z)-3-hexenyl-acetate], at both low and high release rates, were tested to enhance attraction and retention of A. polychrosidis in infested ash trees. Attraction of A. polychrosidis 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 C. fraxinella. More male and female A. polychrosidis 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 C. fraxinella. The high release rate lures did not enhance attraction of A. polychrosidis 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 A. polychrosidis to ash trees infested with C. fraxinella, 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.

Parasitoid complex and bionomics ofApanteles polychrosidis(Hymenoptera: Braconidae) on the ash leaf-cone roller (Lepidoptera: Gracillariidae)

The ash leaf-cone roller,Caloptilia fraxinella(Ely) (Lepidoptera: Gracillariidae) is an introduced leaf-mining moth of horticultural ash trees (FraxinusLinnaeus; Oleaceae) in Western Canadian Prairie cities. Here, we identify the dominant parasitoid of this leaf-mining moth asApanteles polychrosidisVierek (Hymenoptera: Braconidae) and document its emergence pattern, courtship, mating, and host acceptance behaviours.Apanteles polychrosidisadult emergence is protandrous and mating occurs soon after female emergence. MaleA. polychrosidiscan mate multiple times in short sequence with a mean copulation time of 49 seconds. It is likely thatA. polychrosidisoverwinters in an alternate larval host, after emergence fromC. fraxinella. Mated femaleA. polychrosidisreadily parasitise an alternate host, the obliquebanded leafroller (Choristoneura rosaceana(Harris); Lepidoptera: Tortricidae), known to overwinter as larvae. Through rearingC. fraxinellapupae, we describe the remainder of the parasitoid complex ofC. fraxinella, in order of parasitism rate, asDiadegmaFörster (nearDiadegmafenestrale(Holmgren)) (Hymenoptera: Ichneumonidae), threeSympiesisFörster species (Hymenoptera: Eulophidae) (Sympiesissericeicornis(Nees von Esenbeck), one nearSympiesisviridula(Thomson) and one unknown species), andPteromalus phycidis(Ashmead) (Hymenoptera: Pteromalidae) and show that severalSympiesisspecies can be hyperparasitic onA. polychrosidis.Caloptilia fraxinelladensity within the tree canopy is highest in the lower canopy. Host density and abiotic factors such as temperature and light intensity do not influence the within-canopy distribution of most parasitoids exceptSympiesisspecies, which preferred the northern canopy.

Biology of Caloptilia fraxinella (Lepidoptera: Gracillariidae) on ornamental green ash, Fraxinus pennsylvanica (Oleaceae)

The ash leaf cone roller, Caloptilia fraxinella (Ely), is a leaf-mining moth that has recently become a significant pest of horticultural ash, Fraxinus L., species in communities throughout the western prairie provinces of Canada. The study examines the spatial and temporal within-host distribution of immature stages of C. fraxinella on green ash, Fraxinus pennsylvanica Marsh. Female C. fraxinella showed a preference for oviposition sites in the lower canopy and on the south side of the tree at the beginning and middle of the 3-week oviposition period, respectively, but no preference at the end of the period. Oviposition was constrained temporally and occurred mainly just after green ash bud flush. Immature stages were sampled throughout the growing season, and measured widths of larval head capsules showed five instars. Fourth-instar larvae disperse from the mined leaflet to a new leaflet, roll it into a cone, and pupate. Neither canopy height nor ordinal direction affected the position of larvae in the canopy, but numbers of immature stages varied by tree within a site. Female and male moths eclose from rolled leaf cones synchronously throughout the emergence period. The study provides some of the basic biological information required to design an integrated pest management program to target this emerging pest of horticultural ash trees.

Caloptilia fraxinella (Lepidoptera: Gracillariidae), a new pest of ash (Oleaceae: Fraxinus spp.) on the Canadian prairies

In 1999, the leaf roller Caloptilia fraxinella (Ely) (Lepidoptera: Gracillariidae) was noticed for the first time in the city of Edmonton, Alberta, Canada, on ornamental green ash (Fraxinus pennsylvanica Marsh. var. subintegerrima (Vahl) Fern.) and black ash (F. nigra Marsh.) (Oleaceae). It has since been found there on Manchurian ash (F. mandshurica Rupr.) and white ash (F. americana L.). Specimens were collected and reared, and vouchers have been deposited in the Canadian Forest Service Arthropod Collection in Edmonton and the Canadian National Collection of Insects (CNC) in Ottawa, Ontario.