IMO, the best insecticide for tender plants is imidacloprid. You can find it in Bayer Tree & Shrub drench, which is good for large tropicals (a foot or so and up). This is a liquid systemic that you water into the soil. The advantage of a systemic is that it goes into the plant, unlike a spray which lets the bugs live if you miss a spot while spraying.

However, if you want to hit the spider mites at the same time, you might prefer Bayer 3-in-1 Insect, Disease & Mite Control Ready-To-Use Spray. This would also be more suitable than the Tree & Shrub drench for small plants.

Either of these products must be used OUTDOORS ONLY. Check labels for safety precautions.

If you have a large collection, I recommend Marathon II Granules. Same chemical as the Tree & Shrub drench, but you just dump them onto the soil. They are hard to find (I can give you one or two online sources or you need access to a wholesale supplier). Also pricey; they cost about $110 for a jug but it should last you a very long time. They work great. This is what we use professionally on plants we care for inside office buildings.

I'm interested in sources for the Marathon II Granules...a wholesale supplier would be great, as I can provide the necessary documents. I did find a couple sources, but they were higher than $110.

Thank you!

Looks like I got the name a little off - Marathon 1% Granules - sorry about that. Here are two sources I found on a google search:

http://www.growersupply.com/mar1granin.html - $125 on sale for a 5 lb jug

http://www.atlanticfec.com/39-42.htm - $92 for a 5 lb bag but a big delivery fee!

Be sure to follow the directions about not watering heavily for a while after applying. There has been a little scientific research that using this chemical actually encourages spider mite reproduction, but I have not observed it personally and I've seen a lot of plants treated with it. Good luck!

Thanks!

You're very welcome. Good luck keeping those bugs at bay.