I posted the following on GardenWeb’s Rocky Mountain Forum:

I’ve NEVER had a problem with mites like I do now. Is it caused by this unusually hot, dry summer we’ve had? Maybe my trees have had more water stress in this weather, making them more susceptible?

Here’s what’s happening:

Starting in June, I got spider mites really bad on my Granny Smith apple and somewhat less on my Jonathan apple. I’ve been spraying every couple weeks with malathion to prevent codling moth and other pests, but I don’t know if it’s working very well for the mites. I know soap can help, but I’d think malathion would be more effective, don’t you?. Any more serious chemicals I should try?

I also have an Arctic blue willow shrub suffering from mites, and since it’s not a food plant, I could use a systemic insecticide on that one.

Also, one of my young (3-yr old) cherry trees has been hit by mites, too. Not as bad as the one apple, but suffering moderate damage. Then, it suddenly got yellow leaves and dropped a lot of them. It didn’t look like iron chlorosis — I thought maybe it was too dry, so I soaked it with a hose (it only gets drip irrigation from one of those star-pattern sprayer things, and it doesn’t cover the whole root zone). Anyway, then it dropped more leaves, making me wonder if it was actually too wet rather than too dry (after a couple rainstorms last week, it dropped more leaves). Now, it’s growing a new crop of leaves on some of the branch tips. Anyone know how much water cherry trees need? I’m pretty sure I’ve stressed it with inadequate water, which made the mites attack more. I really need to keep this tree alive!