There's been an interesting discussion on the gesneriphile list talking about the use of Marathon systemic granules for insect eradication with regards to people's collections of gesneriads and African violets. Certain insects are very hard to control and this particular chemical has sparked some interest because it seems quite effective. Here's a little information about this chemical, Imidacloprid.
Imidacloprid is a systemic, chloro-nicotinyl insecticide with soil, seed and foliar uses for the control of sucking insects including rice hoppers, aphids, thrips, whiteflies, termites, turf insects, soil insects and some beetles. Imidacloprid is found in a variety of commercial insecticides. The products Admire, Condifor, Gaucho, Premier, Premise, Provado, and Marathon all contain imidacloprid as the active ingredient (223). (Material from EXTOXNET from Oregon State University). Please look at this link to see more information.
Posts from the gesneriphile list have been discussing ways to control mealy and soil mealy bugs. One person, Irina Nicholson was saying, "I join the Marathon afficionadoes. I got a half gallon of it - seems it is a smallest container you can get, paid about $100 for it - but it will last for a long time. I add a half tablespoon per a gallon of soil when repot - and it works for 3-4 months. I had a root mealy bugs infestation in 2004 - and it was the only thing to get rid of them. It keeps off any kind of mealy bugs, fungus gnats and thrips - in their soil and leaf eating stage, it doesn't help against thrips in the buds, though, so if they fly in in summer - I need to disbud everything."
Mel Grice on the firstname.lastname@example.org said "Bayer Advanced Tree & Shrub insect control comes in a 32 oz. blue plastic bottle and contains the same concentration of Imidacloprid as found in Marathon granules. It is a milky white liquid that I mix with water in a watering can and use as a soil drench. A couple of applications a few days apart seemed to solve my mealy bug problems. It doesn't seem to smell and is a lot easier than spraying everything. You can purchase it at Lowe's, Home Depot and places like that. The 32 oz. bottle costs about $20.00 the last time I looked.
Another reader from the list asked about the dilution and application rates. Mel answered, I use ¼ tsp. of the Bayer Tree & Shrub / Imidacloprid in a 1 gallon watering can. It is a systemic insecticide so you want to water the plant when it is slightly on the dry side so that the plant absorbs as much of the solution as possible. I don't like to get out the measuring spoon all the time because I usually spill some of the Bayer. I use a funnel to fill plastic squeeze bottles like you see below with the Bayer T&S. The empty bottles can be purchased at craft, hobby, art stores, etc. in various sizes. They usually have a separate cap and you have to cut off the tip. You get a small hole if you cut it off at the top and a progressively larger hole the farther down you go. I get 20 drops in a ¼ tsp. measuring spoon. You should measure how many drops fit in your spoon the first time you try it."
Usually people have been getting the granular form of imidacloprid under the trade name of Marathon. Many times it seems hard to purchase and expensive for the amount you get. This is perhaps an alternative. I am not endorsing this product or telling you that it's safe for either you or your plants. I'm more of an organic gardener with over 15 years of completely NO chemicals in my vegetable beds and only rare use of systemic fungicides on my heritage peonies that came from my grandmother. (I couldn't bear to lose them.) But, for those interested in a chemical that others have found useful, this might be of some interest. The link and many more like it will provide lots of useable information so that you can make an educated choice of what sorts of chemicals you're exposing yourself to. The comments and picture came from the gesneriphile discussion list.