My oriental lily foliage and stems are now covered with aphids. I thought the foliage was just yellowing until I took a closer look and realized the undersides of the leaves are covered with aphids. I have over 500 lilies and have never had this problem before. About 1/3 seem to be affected. Will the bulbs be affected and can I expect foliage and blooms next summer to be normal? I have washed them off and wonder if I should apply Hort oil or insecticidal soap?