Monitoring of Honeydew Excretion in the Field as a Method of Sampling Illinoia liriodendri (Homoptera: Aphididae) Infesting Liriodendron tulipifera

Honeydew excreted by the tuliptree aphid, Illinoia liriodendri (Monell), was monitored in the field using yellow water-sensitive papers on tuliptrees (Liriodendron tulipifera L.) at two sites in Berkeley, Calif. Significant correlations were found between aphid numbers and honeydew (droplets per hour per square centimeter) except at relatively low densities (approximately four aphids per leaf). Honeydew excretion rate was positively correlated with temperature. The highest rate occurred from 1100 to 1500 hours and the lowest from 1900 to 0700 hours. Monitoring honeydew required 30% less sampling time than counting insects. An efficient method of monitoring tuliptree aphid honeydew will permit more precise timing of spot treatments and could be adapted to monitor other honeydew-excreting insects in the field.