I've had the opportunity to walk through several Christmas tree fields the last couple of weeks. Here are some of my observations.
BALSAM TWIG APHIDS: I'm still not seeing many fields that have high twig aphid numbers. I finally found a couple that did, but mostly there aren't many aphid eggs. Bryan and I found our first live twig aphid on March 30! It was tiny -- just a fist instar. The weather during April will determine how bad twig aphids end up being. Now we're having warm, dry weather which will allow the aphids to quickly hatch, mature, and start to reproduce -- laying live young. If this kind of weather keeps up, those few aphid eggs will turn into plenty of aphids to curl needles by bud break.
We were in one field that had been treated with Talstar in the fall, that actually had a dead aphid sticking out of the aphid egg. But it's still a bit early to be evaluating how these fall aphid treatments are working. Wait until April 15, and then it should be easy to beat aphids out of trees if they are present.
However, if you didn't treat in the fall, and you need to control twig aphids, don't wait until the 15th unless you are using either Di-Syston or Thionex. All other materials including Asana, Talstar (Wisdom), and Dimethoate can be applied now.
BALSAM WOOLLY ADELGID: I visited another field yesterday where several trees were showing symptoms of woollies (flat tops, swollen buds, stiff trunks), but it was extremely hard to find any live woolly on the trees. What we did find were on the buds, and we had to look at lots of buds before we found them. These trees had been completely untreated in 2009. Therefore, I think we're seeing quite a bit of winter kill of BWA, but don't assume they are all killed out. Fields with symptoms of woollies should still be treated for them.
SPRUCE SPIDER MITES: I have yet to find a field with more than just a few spider mite eggs this spring. I'm sure they are out there, but for now, I don't think there are many growers that will have to worry about this pest.
HEMLOCK RUST MITES: Rust mites are really active this spring -- much more so than in the last couple of years. We walked through several fields last week that had been treated in July or August with Dimethoate + Asana to control elongate hemlock scale. This is a combination that should create rust mite problems the following spring, but of the four fields we visited, only one had rust mites. The other fields had virtually no mites.
We walked through another farm this week that had been treated with Talstar in October. It was a very large farm that rambled up and over a ridge, dropping down to the river. On the ridge top, the rust mites were nearing treatment threshold. In other areas of the farm, there weren't any.
So what's a grower to do??? SCOUT!!!! You can find the blocks that need rust mite controls and target only those for treatment. It doesn't take a lot of time to scout. A field of several acres can be evaluated in just 30 minutes. That's worth knowing where you need and don't need rust mite control.
Envidor will provide longer lasting control than just dimethoate. After all, it's a long time until summer. Spring's barely started.