Q: My Alberta spruces are all turning yellow and dying. It started near the top of one and now all 5 are partially infected. I have used several insecticide or fungicide products and Volck Oil with no improvement. The Ortho Book suggests Orthene but I cannot find that anywhere.
The symptoms you describe do not appear to be those of a spider mite infestation. Usually, spider mites will work a certain area, turning it brown or yellow, and they usually aren't covering the whole plant all at one time. Howver, it's not impossible, so check regularly to see if spider mites have paid you a visit.
The best way to check for mites is to hold a white piece of paper beneath the branches and strike them sharply, with the intent to dislodge the mites onto the paper for examination. Wait 10 seconds after doing so, tip the paper slightly to allow bits of plant debris to slide off, then swipe the paper with the back of your hand, with the intention of "smearing" the mites.
Greenish streaks are the bad guys (red streaks are usually the good guy predators). Mites are small, about the size of the period at the end of a sentence, so you have to look hard to see them without benefit of a magnifying lens.
I would caution against the use of oil on a dwarf Alberta spruce -- they're one of the few plants that are sensitive to oil, so you'll want to check the product label for any cautionary statements.
If possible, locate a product containing hexythiazox (this material controls not only adult spider mites but can kill their eggs, too). If you can't find this, I'd stick with a regular miticide (or insecticide if it's labelled for spidermite control). Your local garden center should be able to provide you with what you need.
But it really sounds more like you have a trunk or root problem. When the spruces were planted, the twine may not have been removed from around the trunk at the base, and the plants have grown large enough to get girdled (strangled) in this area. Carefully pull away any debris at the base of the plant and look for such a situation. If found, cut the twine and hope you've caught it in time.
You may also find trunk injury somewhere that has disrupted the flow, or it's possible the root systems have not developed well since their planting, and adverse weather conditions finally took their toll on the plants. It may also be that the roots dried out during extended dry spells, or that the area is too wet, which damages roots as well.
If they totally dry up, I would remove the plants and examine the root systems carefully to see how well (or not) they've developed.
The root system is a critical portion of the plant, and if it's not up to snuff, a plant can be doomed to fail but take quite a while to do so. I would also examine the planting sites to see how well-drained (or not) they may be, and make corrections if need be.
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