I can't comment on hydrogen peroxide but I will add that sanitation does help with mites at my place. The key though is timing and getting them under control. Everything is affected by the weather conditions - even insects it seems. This year we are hot and dry like never before, so no fungus disease but it seems that spruce mites are blowing in my greenhouse windows. The neat thing is, there are some really small spiders that evidently prey on these mites, and they turn up to feed on them. I don't mind reducing their food supply at all by picking off the feeding stations, and when the mites are really in defeat the spiders just disappear from the greenhouse to better feeding grounds. I was at my friend's farm this afternoon pruning and tying her tomatoes - which came from me, with a few mites in tow! - and the same small spiders are still hanging about there (and some big ones!). Plants looking great. But if I didn't pinch off and dispose the damaged leaves, these infestations would get out of control, then the plants suffer too badly and there's nothing left to pick off.
I'm still seeing a few affected leaves now and then near the windows in my greenhouse, so I keep taking them out. I have seen this before and if you let it go without action, the spread is really bad. Not even spiders can eat so many.
So here's hoping the weather and the insect predators cooperate to bring your tomatoes to a lush and happy condition!
