A research report from Alan Knight, USDA–Wapato; Loys Hawkins and Kathleen McNamara, Bear Creek Orchards, Oregon; and
Rick Hilton, Oregon State University
Today, growers have a number of tools to effectively manage codling moth, including sex pheromones, granulovirus, three classes of insect growth regulators, and eight classes of synthetic insecticides attacking different aspects of the insect’s nervous system.
Yet, growers must remain concerned about three aspects of codling moth management: the efficacy of integrated programs, continued selection for insecticide resistance, and rising costs of new technology. Underpinning these concerns throughout each growing season is how best to obtain accurate knowledge of whether and when additional tactics should be applied.
Sex pheromone and pear ester are both potent attractants for codling moth that can allow growers to monitor the status of populations in their orchards. Sex pheromone lures have been widely used for more than 35 years to fix the start of moth flight and allow simple predictions of the start of egg hatch and first spray timing. Unfortunately, sex-pheromone-baited traps in mating-disrupted–orchards too often fail to detect local populations and predict fruit injury.
While pear ester lures were found to be more effective in predicting injury, growers have not adopted their use, likely due to their relatively lower moth catch. Instead, combo lures loaded with a blend of sex pheromone and pear ester, which are more attractive than high-load pheromone lures, have been adopted. Unfortunately, combo lures catch less than 10 percent females, and most growers aren’t sexing catches, thus the full value of this lure has not been utilized.
New trap designs for monitoring codling moth have also undergone some recent rapid evolution. First, white plastic delta traps replaced the standard wing-shaped cardboard trap. Next, studies showed that an orange delta outperformed the white delta trap for codling moth and avoided the catch of nontargets, such as honeybees. The adoption of the orange delta baited with the combo lure has significantly improved growers’ ability to monitor codling moth in sex-pheromone–treated orchards more precisely.
Up to now, the techniques of precision agriculture have not been widely adopted in orchards. Precision management of codling moth can be defined as an approach that restricts the application of sprays to selected sites based on site-specific pest monitoring data (triggers), such as moth catch.
The first step is to map the site and divide the orchard into subunits surrounding each trap. Treatments are then applied to designated areas (portions of or all of one or more subunits) in response to trap catches and consideration of other factors, such as risk preference, spatial factors, pest history, status of other pests and biological control agents in the orchard, and other crop production practices.
This approach was tested in 2008 in two Comice pear orchards situated near Medford, Oregon, in a 51-acre conventional and a 17-acre organic orchard. Both were treated with a grid of Checkmate CM puffers at a density of one per acre. The density of orange delta traps baited with the combo lure was more than doubled from 2007 (see “Codling moth trap comparisons”).
All spray decisions were made by the grower using action thresholds of one or more females and four or more moths per trap. Most sprays applied during the season were triggered by the catch of a single female moth in a trap; however, male catch did trigger a few sprays. No fruit injury occurred in either orchard.
Portions of each orchard were not sprayed with insecticides for codling moth under this program, and this likely increases the opportunities for biological control agents to maintain a range of secondary pest species below economic injury levels. Monitoring costs were higher with the precision program in both orchards due to the increase in traps, but labor and spray costs were considerably lower (see “Orchard costs”).
Total costs in each orchard were about 60 percent less using this precision management approach compared to the costs that would have been incurred if the grower’s standard monitoring and spray protocol had been used.
The future for codling moth management holds a promise of many new and exciting developments. A more potent female lure that combines pear ester with acetic acid has been developed and, in combination with a new clear delta trap, has tremendous potential to improve monitoring of codling moth.
Clear delta traps baited with sex pheromone lures catch similar numbers of moths as standard traps and outperform white delta traps when baited with the combo lure. The most exciting result, however, was that the clear delta trap, when baited with pear ester and acetic acid, caught a similar number of moths as the orange trap baited with the combo lure (see “Trap and lure”).
The significant difference was that the new trap-lure system catches greater than 50 percent female moths compared with the standard trap that caught less than 10 percent female moths.
Adoption of the clear delta trap baited with pear ester and acetic acid has the potential to improve a grower’s capacity to gauge risk and apply supplemental insecticides more judiciously.
This new lure-trap combination may solve two of the major limitations of our past monitoring systems for codling moth: effectively catch females without the need to identify the sex of moths and catch a similar number of moths as our best pheromone lure so that existing thresholds may not have to be changed.
Growers will vary on how they choose to use this new trap-lure system. Likely, several years of field use will be needed to gain sufficient practical experience to establish new action thresholds and to recommend a standardized protocol for trap density and placement in orchards.