Using the Decision Triad for Treatment Thresholds
Three tools are used to monitor populations: predictive models, adult traps, and visual inspections. Understanding the application and limitations of these tools are essential for management decisions.
Trap Placement
Capture of codling moth adults in pheromone traps can be used to estimate population levels and help make control decisions. The number of traps used, their location, trap maintenance and the quality of the pheromone trap are all critical elements to the successful use in a threshold-based decision program.
To implement a threshold-based decision program it is essential to use one monitoring trap for every 2.5 acres. Traps should be placed in the orchard before the accumulation of 175 degree-days (or at the pink stage of apple bud development). Trap placement within the orchard and tree will influence moth captures. Avoid placing traps at the very edge of a block. It is best to place a trap in the center of each 2.5 acre section to be monitored, however, traps may be placed toward an outside border that is impacted by known history of pest high pressure.
Traps should be checked once a week after the first moths are caught. After a total of 30 moths have been captured, or if the trapping surface becomes dirty, the trap bottom or insert should be replaced. Count the number of moths in each trap and remove moths. Record the catch separately for each trap. The idea behind using trap catch as a treatment threshold is that sprays are applied only when moth catch exceeds certain number, the capture threshold.
by Jay Brunner, originally published 1993, revised 2018
Two Methods to Use Moth Capture Data for Sprays
First method (simple)
The trap catch threshold is 2 moths captured on two consecutive weeks. Thus, if a trap catches 2 moths one week and 2 or more the next, a treatment should be applied to the area associated with the trap (2.5 acres). However, if a trap catches 2 moths, then 1 moth, then 2 moths, a spray is not recommended. This method has worked well for growers in British Columbia and Washington.
Second Method (more precise with predictive models)
The codling moth degree-day model is incorporated with moth capture in pheromone traps. The same density of traps is used, one trap every 2.5 acres. Moth capture in a trap is accumulated between 175 to 425 degree-days. The recommended treatment threshold is a total 5 moths, so if 6 or more moths have been captured, then the area associated with the trap should be treated at the 425 degree-day timing. If a treatment is justified based on accumulated moth captures, then moth capture accumulation is started over for the next time period, based either on the expected residue of the pesticide or over the next 250 degree-days. Where codling moth populations are low, it may be possible to delay the treatment decision until 525 degree-days. If by 525 degree-days the moth capture threshold has not been exceeded, then a control treatment should not be applied. If the threshold is exceeded, apply a control treatment as soon as possible. Then moth capture accumulation is started over for the next time period, based either on the expected residue of the pesticide or over the next 250 degree-days.
For the second generation and beyond, the moth capture treatment threshold is reduced to an accumulation of 3 moths, because capture efficiency of pheromone traps is reduced in this time period. Start accumulating moth catch at 1175 degree-days. If 4 or more moths are captured over the next 250 degree-days, a control treatment should be applied to the area associated with the trap. If moth captures do not exceed 3 moths, a control treatment should not be necessary, and the accumulation of moth catch from zero again.
Caution
Control treatments should be applied to the part of the orchard represented by moth capture in the trap that has exceeded the treatment threshold. However, depending on how the orchard is designed, an area larger than that represented by an individual trap may need to be treated. The use of treatment thresholds based on codling moth capture in pheromone traps usually reduces use of insecticides. The treatment thresholds recommended above should only be applied to the individual trap associated with 2.5 acres and should not be used as a threshold based on an average moth capture over the entire orchard. If trap densities are less than on every 2.5 acres, for example one trap per 5 or 10 acres, then the thresholds described above are not applicable and if used could result in unacceptable crop loss.
by Jay Brunner, originally published 1993, revised 2018
Overview on How to Use Traps
Trap placement, density, and lure type are affected by the biology and dispersion of codling moth. Knowing how to interpret counts in relation to prior experience is key in pest management.
Use pesticides with care. Apply them only to plants, animals, or sites listed on the labels. When mixing and applying pesticides, follow all label precautions to protect yourself and others around you. It is a violation of the law to disregard label directions. If pesticides are spilled on skin or clothing, remove clothing and wash skin thoroughly. Store pesticides in their original containers and keep them out of the reach of children, pets, and livestock.
YOU ARE REQUIRED BY LAW TO FOLLOW THE LABEL. It is a legal document. Always read the label before using any pesticide. You, the grower, are responsible for safe pesticide use. Trade (brand) names are provided for your reference only. No discrimination is intended, and other pesticides with the same active ingredient may be suitable. No endorsement is implied.
