Incoming question - Do you know if emergence is or has occurred for the white pine weevil?
A great question for this time of year. I’m not sure if they have emerged but suspect them to emerge anytime now.
In conversations with others on this topic in the past, many felt it was too late really to wait for visual evidence first, in order to apply treatment. The thought was that one would probably miss several of the first adults and they would oviposit before the spray went on. Not sure I would disagree with that.
I’ve noted that Ohio State's Phenological Indicator site has adult emergence at 84 degree days and nearby phenological indicators are first bloom of star magnolia and first bloom of border forsythia. It's been cool but some forsythia is in full bloom. My saucer magnolia is already going gang busters. Not sure what they used as their temperature base for the white pine weevil but base 50 is commonly used so, going with that, I see we are around 75.9 as of yesterday here in Aurora. Prediction is that we hit 84 on 4/18.
I calculated this using the Online Calculator and Degree Day Model. This is a handy site to figure out degree days for a lot of sites in the PNW. I encourage you to play with it and learn more.
So back to timing apps for white pine weevil protection, I’d say jump on it, which doesn’t sound like a scientific phrase but it conveys my meaning. This is one pest where it is better to be too early with an app than too late. Once the eggs are laid, much of the future is ordained.