Attraction of Choristoneura rosaceana (Lepidoptera: Tortricidae) to Pheromone Blends in Ratios Produced in Females’ Pheromone Gland or Emitted by the Females in Michigan Apple Orchards

Trap captures of
obliquebanded leafroller, Choristoneura rosaceana (Harris) to pheromone
blends in ratios approximating those reported in pheromone glands and a novel
blend based on a volatile headspace collection from live virgin females were
evaluated in field experiments in Michigan apple orchards. In an initial field
trapping study, pheromone lures composed of either a three- or four-component blend approximation
of the blend present in female pheromone glands at doses ranging from
0.1 to 20 mg/lure were compared. The four-component blend was a combination of (Z)-11-tetradecenyl
acetate (Z11-14:Ac), (E)-11-tetradecenyl acetate (E11-14:Ac),
(Z)-11-tetradecen-1-ol (Z11-14:OH), and (Z)-11-tetradecenal
(Z11-14:Al) in a ratio of
96.5:1.8:1.4:0.2, respectively, while the three-component blend lacked Z11-14:Al.
Pheromone emissions by groups of virgin females and commercial lures were
collected in the laboratory and analyzed by gas chromatography. These data were
used to formulate a new pheromone lure that was compared to a commercial lure
in a second trapping study. In the first field study, traps baited with 10 mg
pheromones or above captured significantly more moths than traps baited with 1
mg or less, regardless of the blend. Surprisingly, groups of virgin females
only emitted two detectable pheromone components, Z11-14:Ac and Z11-14:OH
in a ratio of 37:63 which was substantially different from the blends detected
in pheromone glands in the literature. The newly formulated pheromone lure
based on females’ emission was more than twice as attractive as the commercial
lure which emitted a 74:5:21 three-component blend of Z11-14:Ac, E11-14:Ac,
and Z11-14:OH. Our results suggested that the actual pheromones
released by females may not translate directly to the content of pheromone
glands.