Alan Taylor has been a Benton County OSU Extension Master Gardener since 2015. When he’s not growing grapes and fruit, Alan puts his scientific background to use at the Master Gardener plant clinic by helping communities, teaching new volunteers and troubleshooting equipment.
If you have ever bitten into an apple and gotten a taste of a worm, there is a good chance it was the larva of a codling moth, a major pest of apples in the Pacific Northwest. Read on to see how Alan uses the data to get ahead of codling moths– and how you can, too!
biofix (plural biofixes)
(biology, pest management) A biological event or indicator of a developmental event, usually in the life of an insect pest, that initiates the beginning of growing-degree-day calculations.
For codling moth, this is the first date of consistent capture of adult moths in pheromone traps, and this year the consensus date for the mid-Valley biofix appears to be 29 April.
Now the fun part: CLICK HERE to visit the IPPC codling moth model (Brunner and Hoyt).
This link to the degree-day model gives a map to let the user select the weather station, and the correct biological model has already been selected. The user will need to enter the biofix date (I’ve been using 29 April) and then the calculations will give the appropriate dates for spraying.
For example, I clocked on a weather station in SW Corvallis, then entered 4/29 as starting date. This gives 20% hatch at 6 June and 50% hatch at 18 June. These two dates are the timing of the two sprays of insecticide for the first generation of codling moth.
Then I selected a site NW of Corvallis with an elevation of 780’, more representative of where I live (unfortunately no good sites both to the SW and at elevation are shown in the map), and the prediction is 20% hatch on 11 June and 50% hatch on 23 June. You can see the effect of a cooler location or microclimate. I have consistently noted that bloom and ripening of my fruit (apples, pears, grapes, etc.) is 7 – 10 later than that of friends down in Corvallis. Being at ~700’ and somewhat closer to the coast does make a difference, and I’ll be allowing for that in my sprays this year. Realistically, this is a conservative estimate, because I should also have a later biofix at my site, but I’ve chosen to ignore this. Last year, I used the timing for the Valley sites, and my apples were very clean.
Just to complicate things, not all insecticides remain effective for 12 days. I think spinosad, which I used, is supposed to be good for 10 days. Always compromises, so I used the model timing of the first spray, then waited 10 days for the second spray.
Finally, there are 2 and sometimes 3 generations of codling moth in the Valley. I’ll use the model to predict the spray timing for the second generation (we can cover that later), and I chose to ignore the potential 3rd generation last year. Four sprays is enough!
Read more about codling moths and how to manage them in the Pacific Northwest Insect Management Handbook.
Managing Diseases and Insects in Home Orchards is another useful guide.
“Project Happy Apples: Reducing codling moth damage in backyard orchards” is a free webinar for Master gardeners and home orchardists alike. Watch it HERE.