Harmonic radar tracking of individual melon flies, Zeugodacus cucurbitae, in Hawaii: Determining movement parameters in cage and field settings

Authors: MILLER, N - Eastern Mennonite University; YODER, T - Eastern Mennonite University; Manoukis, Nicholas; Carvalho, Lori; SIDERHURST, M - Eastern Mennonite University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2022
Publication Date: 11/16/2022
Citation: Miller, N., Yoder, T., Manoukis, N., Carvalho, L.A., Siderhurst, M. 2022. Harmonic radar tracking of individual melon flies, Zeugodacus cucurbitae, in Hawaii: Determining movement parameters in cage and field settings. PLOS ONE. 17(11). Article e0276987. https://doi.org/10.1371/journal.pone.0276987.
DOI: https://doi.org/10.1371/journal.pone.0276987

Interpretive Summary: We have tracked individual tagged male melon flies using harmonic radar (HR). We are able to detect a light weight diode and antenna attached to the insect using a hand-held device. Information gathered from field cages and open field experiments in parkland and a papaya grove showed directed movement: Melon flies are not moving in random directions. Wind appears to not be the only factor affecting direction. This information will be important for developing more effective control measures against this pest (for example, setting the distance of treatment more accurately).

Technical Abstract: Tephritid fruit flies, such as the melon fly, Zeugodacus cucurbitae, are major horticultural pests worldwide and pose invasion risks due primarily to international trade. Determining movement parameters for fruit flies is critical to effective surveillance and control strategies, from setting quarantine boundaries after incursions to development of agent-based models for management. While mark-release-recapture, flight mills, and visual observations have been used to study tephritid movement, none of these techniques give a full picture of fruit fly movement in nature. Tracking tagged flies offers an alternative method which has the potential to observe individual fly movements in the field, mirroring studies conducted by ecologists on larger animals. In this study, harmonic radar (HR) tags were fabricated using superelastic nitinol wire which is light (tags weighed less than 1 mg), flexible, and does not tangle. Flight tests with wild melon flies showed no obvious adverse effects of HR tag attachment. Subsequent experiments successfully tracked HR tagged flies in large field cages, a papaya field, and open parkland. Unexpectedly, a majority of tagged flies showed strong flight directional biases with these biases varying between flies, similar to what has been observed in the migratory butterfly Pieris brassicae. In field cage experiments, 30 of the 36 flies observed (83%) showed directionally biased flights while similar biases were observed in roughly half the flies tracked in a papaya field. Turning angles from both cage and field experiments were non-random and indicate a strong bias toward continued “forward” movement. At least some of the observed direction bias can be explained by wind direction with a correlation observed between collective melon fly flight directions in field cage, papaya field, and open field experiments. However, individual mean flight directions coincided with the observed wind direction for only 9 out of the 25 flies in the cage experiment and half of the flies in the papaya field, suggesting wind is unlikely to be the only factor affecting flight direction. Individual flight distances (meters per flight) differed between the field cage, papaya field, and open field experiments with longer mean step-distances observed in the open field. Data on flight directionality and step-distances determined in this study might assist in the development of more effective control and better parametrize models of pest tephritid fruit fly movement.