Codling moth (Cydia pomonella) is the primary insect pest of apple and pear trees in Montana and can destroy an entire crop if uncontrolled. Understanding the moth's life cycle is important for determining management methods and timing of treatments. The purpose of this study was to compare trap-based biofix (first consistent moth capture in the spring) to two temperature based trap-free models for fixed biofix developed in other apple producing regions. Trap-free models determine a date for fixed biofix using temperature accumulation data (growing degree days) from nearby weather stations. Trap-free models compared in the present study were developed and are used in Washington state and Utah state; compared to Montana, Washington is similar latitude but lower elevation, and Utah is similar to higher elevation, but lower latitude. Results presented here suggest that the Washington state model for fixed biofix more closely aligns with Montana trap-based biofix in the 3 years of the study. Generally, trap-based biofix in Montana occured after the Washington state model fixed biofix growing degree date; we surmise that low evening temperatures and frequent high winds in some parts of the state and certain years could influence trap catch.

Data were collected in 2018, 2019, 2020 by a combination of Montana State University (MSU) staff, fruit growers, or volunteers. Data collected by paid staff are indicated in the dataset. We would like to thank all staff, fruit growers, and volunteers who assisted with this study.

Trap-based biofix dates were established by hanging Trece Pherocon III Orange Delta traps equipped with a 1-month Trece codling moth lure in apple trees in participating orchards around 100 growing degree days (GDD) after January 1 (50 degrees Fahrenheit base threshold, 88 degrees Fahrenheit maximum, single sine calculation method, horizontal cutoff); GDD for the orchard were determined using the nearest weather station with GDD data available through USPest.org. Personnel collecting data were instructed to check traps daily for adult male codling moth until biofix was established.

Fixed biofix dates were determined using a USPest.org GDD accumulation (as described above) from the weatherstation nearest to the orchard combined with fixed biofix GDD per the Washington state method (175 GDD) and the elevation and latitude specific Utah state fixed biofix GDD calculated per this equation:

GDD in Fahrenheit = (1755.559-(66.777*latitude)+(0.676*(latitude^2))-(0.0347*elevation in m))*1.8

Differences between trap-based biofix and fixed biofix dates for the two models are compared in the dataset.

References for the fixed-biofix models are:

Washington state method (Model 1):  Jones, VP, Doerr, M, Brunner, JF. 2008. Is Biofix Necessary for Predicting Codling Moth (Lepidoptera: Tortricidae) Emergence in Washington State Apple Orchards? J. Econ. Entomol. 101 (5):1651-1657.

Utah TRAPs method (Model 2): Jones, VP et al 2013.  Predicting the emergence of the codling moth, Cydia pomonella (Lepidoptera: Tortricidae), on a degree-day scale in North America. Pest Management Sci., 69:1393-1398.

This dataset will be a reference for a MSU Extension Bulletin titled "Managing codling moth (Cydia pomonella) in Montana" (currently in draft, 10/9/2020) where we will make recommendations for codling moth management in Montana, including which trap-free model to use.

Definitions

Growing degree days (GDD) are units of daily heat accumulation calculated using daily or hourly temperature data. 

Biofix is the date when two adult codling moths are trapped two nights in a row in the spring.

Trap-based biofix is synonymous with biofix and refers to the date when two adult codling moths are trapped two nights in a row in the spring.

Fixed biofix is the date, per calculations based on GDD, when adult codling moths emerge from pupae and begin flying and mating.  Fixed biofix GDD vary between the two models compared in this dataset.