 When you're out scouting, sample at least 20 to 30 plants per field. What I always do is pull them out of the ground, turn them over. The aphids tend to be on the bottom of the leaf. Look at those leaves, and if you're averaging over 250 per plant, that's kind of the treatment level. 250 aphids per plant on an average, it does not look like much at all. There's not going to be plants dripping with honeydew or anything like that. Potter says to also weigh the economic injury level with the economic threshold.