Now is the time for soybean aphid. Turn over leaves and estimate aphids per plant.
Have you ever tried Speed Scouting to make treatment decisions for soybean aphid? In an area with lots of soybean aphid, this sampling method can greatly reduce the amount of time it takes to decide if an application is needed. I've got blank Speed Scouting forms available here. Or you can take a look at a blank form below.
It's easy to use and most importantly can save a lot of time (hence the name!). You only have to count to 40. Once you get to 40 - stop and consider that plant infested. Look at 11 plants to get started and then use the decision matrix to get the sampling decision. Most of time you will know if you should treat or not in less than 15 minutes.