FACTORS AFFECTING CATCH IN PHEROMONE TRAPS FOR MONITORING THE WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALIS FREEMAN

Abstract

The effects of trap design, lure concentration, lure age, and trap maintenance on the catch of western spruce budworm moths, Choristoneura occidentalis Freeman, in pheromone traps were tested in light to moderate infestations near Ashcroft, B.C. High cumulative moth catches reduced the trapping efficiency of both the sticky traps and the non-sticky Uni-traps relative to traps from which the moths were removed every 2 days. Correlations between the total season’s catch and larval density per plot in the same and following generations were not significant (P>0.05) for any of the eight combinations of trap design, lure concentration, and maintenance regimen tested. However, by dividing the mean moth catch in Uni-traps by either the basal area or foliage biomass per hectare in each plot, correlations with the following year’s larval density were significant (r2 = 0.77–0.98; P<0.05; n=5).

Population monitoring of the pine processionary moth (Lepidoptera: Thaumetopoeidae) with pheromone-baited traps

“…Trap design, placement and density can also affect the number of moths captured (Cuevas et al, 1983a;Einhorn et al, 1983;Ramaswamy and Carde, 1982;Subchev et al, 1994;Tiberi and Niccoli, 1984;Lopez, 1998;Cork et al, 2003). Yet another factor may be trap saturation, with many studies showing a decrease in trap efficiency with increasing number of catches (Ramaswamy and Carde, 1982;Allen et al, 1986;Elkinton, 1987;Sweeney et al, 1990;Gray et al, 1991;Thorpe et al, 1993;Morewood et al, 2000). Some authors describe a decrease in pheromone-trap efficiency with increasing local insect population density, interpreting it as a result of competition between pheromone dispensers and numerous wild females for male attraction (Cornic et al, 1986;Taylor et al, 1991).…”

“…On the other hand, Baronio et al (1994) observed a significant relationship between densities of winter nests and sum captures of T. pityocampa males in the same pine stands. In addition, pheromone-based monitoring has been used successfully for many other forest moths, such as the eastern spruce budworm (Ramaswamy et al, 1983;Allen et al, 1986;Sanders, 1988), the western spruce budworm (Sweeney et al, 1990), the gypsy moth (Ravlin, 1991), the nun moth (Morewood et al, 2000) and the western hemlock looper (Evenden et al, 1995). Monitoring systems based on pheromone trapping have even been developed to predict defoliation (Shepherd et al, 1985;Thorpe et al, 1993;Evenden et al, 1995;Sanders, 1996).…”

“…The lack of correlation between trap captures and population levels may also originate from the way the latter is estimated. While pheromone traps collect flying male moths at the stand level, larvae counts are often performed at the tree level (Sweeney et al, 1990;Morewood et al, 2000). Allen et al (1986) improved correlations between larvae density estimates and trap captures of the spruce budworm by increasing the number of sampled trees.…”

The influence of Canadian research on semiochemical-based management of forest insect pests in Canada

“…Non-saturating traps can retain large numbers of insects, which is particularly useful when traps remain in the field for the duration of the flight period. Even non-saturating Unitraps were less efficient in capturing western spruce budworm moths, Choristoneura occidentalis (Walsingham) (Lepidoptera: Tortricidae), when traps were not regularly maintained throughout the flight season (Sweeney et al 1990). Captured moths will decay if traps are deployed for long periods, and this can affect moth orientation to the trap (Sanders 1986b) and make the sample difficult to count.…”

“…If this relationship is robust, pheromone-based monitoring can replace more costly sampling techniques such as foliage samples, or samples of immature stages (Sanders 1988). These types of relationships have been established for forest defoliators in Canada by sampling populations over long periods of time (Sanders 1988) or targeting populations of differing densities over a condensed period (Shepherd et al 1985;Sweeney et al 1990;Evenden et al 1995a).…”