Managing Codling Moth (Lepidoptera: Tortricidae) with an Internal Grid of Either Aerosol Puffers or Dispenser Clusters Plus Border Applications of Individual Dispensers

Journal of the Entomological Society of British Columbia, Dec 2004 by Knight, A L

ABSTRACT

Field trials run from 2001 to 2003 evaluated the effectiveness of a combination of hand-applied sex pheromone dispensers (Isomate-C) applied on the perimeter of apple orchards with an internal grid of either pressurized aerosol emitters (puffers) or clusters of dispensers for control of codling moth, Cydia pomonella (L.). Puffers were placed in a grid at 1 per ha, while the dispenser clusters were applied at 4 - 8 per ha. Puffers were programmed to release either 240 or 360 mg (E, E)-8-10-dodecadienol (codlemone) per day in 48 puffs (every 15 min from 1500 - 0300 h). Dispensers were grouped in clusters of 50 (Isomate-C TT) or 100 (Isomate-C PLUS) releasing 56 and 33 mg codlemone per d, respectively. No significant differences were found in levels of fruit injury in puffer-treated orchards paired with similar orchards treated with 500 Isomate-C PLUS individually applied dispensers per ha. Similarly no significant differences in fruit injury were found in orchards treated with individually applied dispensers versus orchards treated with Isomate-C PLUS dispensers (100 per cluster) placed in screened cages or Isomate-C TT dispensers (50 per cluster) hung from plastic disks. Levels of fruit injury, however, were significantly higher in orchards treated with Isomate-C PLUS dispensers (100 per cluster) hung from plastic disks versus in orchards treated with individually applied dispensers. This later poor performance of the Isomate-C PLUS clusters was associated with its more restricted spacing of dispensers within the cluster and a significant reduction in the weight loss of dispensers compared with dispensers applied individually. These studies suggest that the use of puffers can effectively lower the cost of codling moth management through reductions in sex pheromone puff volume and emitter density.

Key Words: mating disruption, sex pheremones, puffers, apple

INTRODUCTION

Since 1990, uniformly distributed hand-applied dispensers loaded with (E, E)-8-10-dodecadienol (codlemone) have been the most commonly used approach to disrupt mating of codling moth, Cydia pomonella (L.) in North American tree fruit and nut crops (Thomson et al. 2000). Major problems associated with the use of hand-applied dispensers have been maintaining the chemical stability of codlemone (Brown et al. 1992; Millar 1995), seasonal variability in emission rates primarily due to changes in temperature (Howell 1992; Knight 1995a), material cost (Alway 1997), and the labor cost of applying hundreds of dispensers per hectare (Knight 1995b; Williamson et al. 1996). High emission, timer-activated mechanical aerosol dispensers (puffers) have been suggested as an alternative that can solve some of these problems (Mafra-Neto and Baker 1996; Shorey et al. 1996; Isaacs et al. 1999). Puffers are used at a low density, can protect sex pheromones from UV degradation and oxidation, allow the application of a consistent pheromone release rate throughout the season, and allow users to adjust the cycle and periodicity of sex pheromone release (Shorey et al. 1996).

Shorey and coworkers postulated that effective mating disruption depended on the concentration of sex pheromone released per area and was not significantly affected by the spacing between individual point sources (Farkas et al. 1974; Shorey et al. 1996; Shorey and Gerber 1996a, b, c). They showed that the distance between pheromone sources could be quite large. For example, a perimeter application of emitters 100 m apart effectively disrupted Platynota stultana (Walsingham) and Spodoptera exigua (Hübner) mating (Shorey et al. 1996).

Puffers were initially evaluated for codling moth in walnuts where tree height and large canopy size had precluded the adoption of hand-applied dispensers (Shorey and Gerber 1996b). A single orchard was treated with 2.3 puffers per ha with units spaced 40 m apart along its perimeter. Puffers were programmed to release approximately 5.0 mg codlemone per puff every 30 min (254 mg/ha per d). Moth catches in traps baited with synthetic lures and virgin females were reduced 95 and 98% in this orchard versus in traps placed in an untreated orchard (Shorey and Gerber 1996b). The current standard protocol for codling moth control with puffers recommends the use of 2.5 - 5.0 puffers per ha arranged primarily around the perimeter of orchards. However, in large blocks (> 16 ha) a few puffers are placed along the upwind interior of the orchards (Elkins 2002).

Four major problems have occurred with the use of puffers for management of codling moth. First, placement of puffers on the perimeter of orchards has not been effective in preventing injury along the upwind edges of the orchards (Shorey et al. 1998). Greater wind speed and turbulence plus higher moth population density along orchard borders are problematic with this approach (Milli et al. 1997). A second problem has been their high cost. The fixed cost of individual cabinets housing the electronics ($40 amortized over 5 y) plus the yearly cost of the disposable pheromone-loaded canisters ($80) often limits the number of units deployed. Hand-applied dispensers in Washington State are typically applied at rates of 500 per ha and cost $125 per ha (Alway 1997). To be cost competitive puffer density should be 1.5 2.0 units per ha. A third problem has been the loss of units during the season due to wind, vandalism, and a variety of mechanical malfunctions. The unreliable performance of puffers has required expensive maintenance and frequent monitoring of units (Knight 2002). A fourth problem has been the occurrence of severe marking of fruit and foliar phytotoxicity surrounding units due to incidental contact with the sex pheromone solution (Giroux and Miller 2001).

An alternative approach was developed that alleviates some of these constraints (Knight 2002). Orchards are treated with an internal grid of puffers spaced 50 m from the border and 100 m apart (one puffer per ha) in combination with a perimeter application of hand-applied dispensers (1,000 per ha). This design was tested in apple orchards for codling moth alone or codling moth and obliquebanded leafroller, Choristoneura rosaceana (Harris), using canisters loaded with the sex pheromone of both species (Knight 2002). This method provided good control of both pests at a lower cost per ha than the use of uniformly distributed hand applied dispensers. However, these studies were only conducted in large, regular-shaped orchards with flat terrain and have not sufficiently addressed the utility of this approach in smaller, irregular-shaped orchards with sloping topography (Knight 2002). The initial success of this approach also suggests that lower puffer volumes of sex pheromone should be evaluated. Unfortunately, problems with the reliability of the puffer units and phytotoxic effects persisted in this study and grower adoption has been slowed by these problems. An alternative design has been proposed that would replace the mechanical puffers with clusters of hand-applied dispensers to generate high emission point sources (Knight 2002).