Seasonal visitation of insects to honeydew on crape myrtle trees in urban landscapes

Crape myrtle is a predominant ornamental tree in urban landscapes throughout the southeastern United States. Crape myrtle bark scale (Acanthococcus lagerstroemiae) and crape myrtle aphid (Sarucallis kahawaluokalani) are among the few pests of crape myrtle. These exotic sap-sucking pests have resulted in widespread use of systemic insecticides on crape myrtle trees. Both pest species produce honeydew, the sugar rich excretion product of phloem feeding insects. Honeydew has been implicated as an important sugar resource for beneficial flies and wasps and insecticide residues were recently reported in honeydew at lethal levels. This study explored how honeydew affects seasonal insect visitation to crape myrtles through the following two questions: What beneficial insects using honeydew on crape myrtle trees at varying times throughout the year? Does the time of year affect honeydew production? A field experiment measured the abundance and diversity of insects that visited potted trees, uninfested or infested with S. kahawaluokalani and A. lagerstroemiae. Potted trees placed in landscapes for 2 days per month (June-Oct, 2020 and March-May, 2021), were monitored every 3 hours from 0600-1500 hours. . Visual surveys and selective netting were used to confirm identifications.  Plate collectors were used to determine monthly honeydew production from landscape trees and from trees used in the visitation experiment. Honeydew collections (48 h) were eluted and dried to determine weight produced at each evaluation. The results show that the presence of phloem feeding insects and the associated honeydew on crape myrtle changes community diversity of hymenoptera and diptera visiting crape myrtles.