Aphids are most active in cool weather spring and fall in temperate zones, and all winter long in the subtropics. Controlling daylily aphids is not as easy as with other kinds of aphids, which are usually vulnerable to such soft controls as soaps. In order to reach daylily aphids inside the fans, a pesticide with at least a mildly systemic action is needed. Do not use the pesticide Kelthane, which is known to harm daylilies. Spider Mites Spider mites are among the most common daylily pests.
Spider mites are most active in hot, dry weather.
You can get some control of spider mites just by hosing them off as needed. Thrips Several species of thrips are know to infest daylilies. Control thrips by starting early in the growing season with a pesticide having either a systemic or long residual action. To repeat, do not use the pesticide Kelthane. Slugs and Snails Slugs and snails feed on the young, tender tissues, causing ragged edges and holes.