@ajao,

I think you sow the soybean crop in a closed/controlled chamber. When the crop will reach the stage of pest attack, you have to allow the pest to attack the crop. For this you need a population of the pest. If you can arrange all this, you can try this method.

Otherwise in open field it will be difficult to record that which plant is attacked by the pest. If there are some particular symptoms that appears only after the attack of the pest in question, you can study the seeds and pods of the affected plants.