Inhibitory Effects of Semiochemicals on the Attraction of an Ambrosia
Beetle Euwallacea nr. fornicatus to Quercivorol
John A. Byers
Received: 8 February 2018 /Revised: 2 April 2018 /Accepted: 9 April 2018 /Published online: 17 April 2018
Springer Science+Business Media, LLC, part of Springer Nature 2018
The Euwallacea fornicatus (Eichhoff) species complex includes the polyphagous shot hole borer (PSHB), an ambrosia beetle infesting
avocado limbs, Persea americana Mill. Synthetic quercivorol, a monoterpene alcohol, is known to attract females (males are flightless)
over a range of release rates spanning three orders of magnitude. The upper release dose was extended 10-fold using sticky traps baited
with quercivorol released at 1× (0.126 mg/day), 10×, and 108× relative rates to obtain a dose−response curve fitting a kinetic formation
function. Naturally infested limbs of living avocado trees were wrapped with netting to exclude the possibility of catching emerging
beetles on the encircling sticky traps. The results indicate PSHB are significantly attracted to infested limbs. Ethanol released over a 64-
fold range (lowest rate of 7.5 mg/day) was moderately inhibitory of PSHB attraction to 1× quercivorol. β-caryophyllene and eucalyptol
did not appear to affect attraction at the rates tested. A field test of potential inhibitors of 1× quercivorol was done using ~1 mg/day
releases of monoterpene ketones: (−)-(S)-verbenone, (+)-(R)-verbenone, 3-methyl-2-cyclo-hexen-1-one (MCH or seudenone),
piperitone, (+)-(S)-carvone, and racemic cryptone. Only piperitone and the two enantiomers of verbenone were strongly inhibitory.
A blend of piperitone and verbenone tested together at different distances (0, 0.5, 1, 2, and 4 m) from a 1× quercivorol baited sticky trap
became increasingly ineffective in inhibiting the attractant as separation distance increased. Due to the relatively short-range repellency
(<1 m), the inhibitors would need to be released from several places on each tree to effectively repel PSHB from avocado trees.
Effective attraction radii, EAR, and circular EARc are estimated for the quercivorol baits released at 1×, 10× and 108× rates. Push-pull
simulations of moving beetles were performed in 1 ha plots with 2, 4, or 16 traps of 10× EARc and 400 trees (0, 1, or 3 inhibitors per
tree) of which ten had an infested limb (EARc = 0.5 m). The simulations indicate that push-pull methods would be more effective in
reducing PSHB mating than simply using mass-trapping alone.
Effective attraction radius
Theambrosiabeetle,Euwallacea fornicatus (Eichhoff)
(Curculionidae: Scolytinae) comprises a species complex of
at least three cryptic species that includes the polyphagous
shot hole borer (PSHB) which originated in Southeast Asia.
PSHB invaded California about 2003, and shortly thereafter
Israel (Eskalen et al. 2012; Freeman et al. 2012;Mendeletal.
2012). Another important species of the E. fornicatus complex
is the tea shot hole borer (TSHB), originally from Sri Lanka,
which has become a pest in Florida (Carrillo et al. 2015, 2016;
Cooperband et al. 2016). These two species and a third,
Kuroshio shot hole borer (KSHB), are morphologically indis-
tinguishable but differ in host preferences, fungal symbionts,
and DNA geographically (Eskalen et al. 2013; Freeman et al.
2012;O’Donnell et al. 2015;Stouthameretal.2017). PSHB
has a relatively broad host range of woody shrubs and trees
and may carry Fusarium dieback disease (Cooperband et al.
2016; Eskalen et al. 2013; Freeman et al. 2012; Lynch et al.
2016). In Israel, PSHB is a pest of avocado because beetle
infested limbs die reducing tree growth over time (Freeman
et al. 2012;Mendeletal.2012). Like other ambrosia beetles,
* John A. Byers
Department of Entomology, Robert H. Smith Faculty of Agriculture,
Food and Environment, The Hebrew University of Jerusalem,
The Israel Fruit Growers Association, Yahud, Israel
Synergy Semiochemicals, Burnaby, British Columbia, Canada
Institute of Plant Protection, Agricultural Research Organization,
Volcani Center, Rishon LeZion, Israel
Journal of Chemical Ecology (2018) 44:565–575