Update- May 2013- This post still seems like it is getting a lot of traffic! Full origional post below the image, but here is a quick update. They Bayer product noted below seems to be the winner. My first application kept me bug free for years. I had one bush have another outbreak last year, and one application fixed it again. In the comments below, EMiller left this helpful info- The active ingredient in the formula is Imidacloprid (the original formula also has another chemical but it’s not used anymore). Amazon sells different brands that contain Imidacloprid, here’s a link to the Bayer concentrate: clicky
Secondary update- Late June 2012- I see the popularity of this post is still growing, and wanted to give an update. The Bayer solution noted below that requires you to pour a bucket of their mixture at the base of the plant worked, and kept me totally bug free for aprox 3.5 years!!! This spring, the little buggers were back, and I re-treated them about 2 months ago. I used a hose spray solution (of the same mix, they also sell it that way) to quickly kill them so I could de-sticky my deck/patio furniture for a party I was having the same weekend. At the same time I applied a bucket of the “Tree and Shrub Protect and Feed” and have been bug free since. Below are the pics of the product and label. I know they change the names/packaging over the years. All of the other solutions tested below, and most of the ones in the comments are very temporary. This is the only thing I have done that has kept them away for more than a month.
When I bought my house last year, I told myself that I would give myself one year to see if I could figure out a way to control the aphid/spider mite infestation that all 3 of my Crepe Myrtles had. For those not familiar with the issue, the aphids infest the bottom sides of the leaves. Once there they eat the sap and then proceed to crap the sap out on whatever might be below. This aphid crap is affectionately known as “honeydew” by some, but I like to call a spade a spade and refer to it as aphid crap. You feel it as tiny mist like drops falling from the tree above. If the infestation is bad, the mist can be heavy and annoying. It is also sticky and will get all over any furniture or deck that it is above. Heavy infestation can also cause mold and other problems for the plant. Since I have one large crepe myrtle that is in the middle of my deck that provides shade in the summer, I have been determined to see if I could control the problem so that I would not have to cut the tree down. That sounds harsh, but the shade the tree provides is useless if nobody wants to sit in the mist of aphid crap. It basically makes the deck unusable.
All this black crap that I had to power wash off of my deck was caused by the aphid honeydew.
This year I tried to take a scientific approach. Since I had 2 in the front yard, and one Crepe Myrtle in the front yard that were infested, I though I would try 2 different products to see which one worked best.
Update: I see this post still gets a lot of traffic, so I thought I’d share this update. The year after I wrote the post below, I used a Bayer 12 month systemic insecticide. You mix it in a bucket of water and pour it at the base of the plants. It wiped out the problem completely and hasn’t ever required a reapplication. The bushes have been Aphid free for the past 2-3 years now!
First up- Ortho Total Kill- Lawn and Garden Insect Killer. The list of bugs that it kills includes mites and aphids, and it also claims that it has long lasting effects, and keeps killing after application. I used this on the Crepe Myrtles in the front yard. Over a period of a few days, it did kill a lot of the aphids, but it didn’t do a real good job. After checking out ground zero a few days later, it looked like about %70 of the bugs were dead on the back of the leafs, but the rest were alive and well.
Next up- Ortho Systemic Insect Killer- This stuff rocks. Within 24 hours there was not a living aphid to be found. It totally killed all of the mites and aphids, and kept them gone for about one month before I started to notice a few bugs starting to come back. This one is the winner for sure. I think if I spray with this product about once a month, I can control the aphids, and live on a deck that is free of aphid crap.