Dormant oil as part of Codling Moth Control

Of course if TMin>TThreshold, then GDD=DD, and you skip the trigonometry, which is simple enough but only good during warm weather.

But I’m surprised that GDD accumulates so much before bud-break in the South. I’ll have to look into this.

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Hi. I found a very good resource that helped me immensely last year with knowing where I was on degree days and generations of codling moth, etc. It also has numerous plant diseases and pests for multiple fruit and vegetables . You can pick a weather station close to you and set the threasehold of what you want for degree days. It’s helped me as well with forecasting fire blight danger.
I’m really confused this year and hopeful that maybe the little guys got frozen when we had a warm weather and then abrupt 20’s. I also sprayed mit-e oil at 1/4 green tip. I just haven’t seen any moths in traps at all. We started full bloom a couple days ago and I think the apples are at about 375 degree days. It would sure be helpful if there really aren’t many but maybe my traps just are not working. I put up mating disruptors two weeks ago. We normally go through several generations of moths here because it can be in the 80s in October. We usually sprayed intrepid every 10-14 days and last year I also alternated a generation with altacor. It seemed to work well. Any suggestions? Thanks.


From a commercial perspective, it’s very difficult to manage IPM on a degree day model in this area. The reason is because most of the insects have different DD schedules. Here in humid country we fight multiple insects, so it’s impossible to focus on one IPM DD schedule for one species. OFM has a one month reproductive cycle, so it’s season long. OFM is an apple pest when you grow stonefruits close by.

Then you have something like stinkbug which is also season long. If you ignore them, you’ll get a bunch of catfaced fruits which are either impossible to sell, or sell at a loss.

Honestly, IPM here is more of a gut feel than a science. When it doesn’t rain, we can lengthen the spray interval significantly. If it’s raining regularly, we have to stick to a schedule. This kind of stuff isn’t in the literature (yet) at least for my area, it’s almost like you have to develop a feel for it. Heat and dry slows down all your insect pests, regardless of their individual reproductive cycles.


Golden Noble is at ¼" green, and I’ve let slip yet another opportunity to apply dormant oil because it’s just too warm and breezy today. I’m beginning to accumulate growing degree-days in the run-up to bloom and the first flight of the codling moth. I know that most of you to the south have long since reached this stage. What surprised me was that you were able to accumulate so much growing degree-days before bud break, and this caused me to try to reevaluate my notions of when bloom and codling moth first flight occurs. Sadly, this does not seem to be very simple. I’m with @Olpea:

This kind of stuff isn’t in the literature (yet) at least for my area.

Apple bloom and codling moth first flight occur at different times in different years and in different places, but they are nearly always simultaneous in a given year in a given place even though they are separate phenomena. This is odd because, while apple trees are induced to bloom by duration of temperatures around freezing that they experience during the winter followed by excursions of warmer weather in the spring, codling moths are induced to break diapause and pupate by changes in photoperiod. The swindle here is that local strains of codling moth have adapted to emerge at about the time that apple comes into bloom in a given region.

I did find an old reference that describes the problem from the point of view of culturing codling moth for research purposes:

The article laments the lack of research into regional differences, while detailing the great effort required to verify models in the lab.

Suffice it to say that the timing of 250 growing degree-days Fahrenheit between first flight and the beginning of egg hatch is more or less consistent from year to year and place to place and thus forms the basis for chemical-treatment protocols. Because neither bloom nor first flight can be predicted accurately, they must instead be observed, so you really have to set your pheromone traps to be sure when first flight is occurring.


We’re still waiting for the leaves to unfold on the apple, but the pear is trying to bloom. I’m trying to finesse my dormant oil spray to cover both at the same time but probably won’t get away with it. Tomorrow is supposed to be nice, so I should have a chance to hit the pear then, and I’ll just use up the leftover on the apple. Then I’ll have to hit the apple again when the blooms want to open.