Title: Oriental Fruit Fly: Males-Only Sterile Fly Releases in Hawaii Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 20, 2005
Publication Date: March 7, 2005
Citation: Mcinnis, D.O., Lim, R.R., Muromoto, D.S., Komatsu, J., Tam, S.Y., Murasaki, N.M. Oriental fruit fly: males-only sterile fly releases in Hawaii. The 8th Exotic Fruit Fly Symposium. Riverside, California. March 7-9, 2005. P.34. Interpretive Summary: Abstract only.
Technical Abstract: Beginning in late August, 2004, we began a program to release sterile male oriental fruit flies, Bactrocera dorsalis, in a citrus orchard in central Oahu, Hawaii. This program follows the encouraging results obtained with the melon fly genetic sexing strain on the islands of Hawaii, Maui, and Oahu. The oriental fruit fly sexing strain is like our melon fly sexing strain in being based on a white pupal color system in which females emerge from white pupae and males emerge from normal brown pupae. Efficient color sorting machines are used to separate the white from brown pupae and provide a virtually all-male sterile population for field release. The sterile insect technique has been shown to be significantly more effective when only sterile males are released into the field. Since the oriental fruit fly sexing strain was made some 10 years ago by University of Hawaii entomologists (Drs. Susan McCombs and Stephen Saul), the strain has been tested for quality both in the laboratory and in field cages. It has proven to be a very competitive strain worthy of mass-production and release into the field. For 4 months (Sept.-Dec.), we made weekly releases of up to 300,000 sterile males into the 15 ha orchard. We started with 5 weeks of single point releases to measure sterile fly dispersal and longevity from a central release point. Following those first 5 releases, we made releases at 10-12 points spaced within the. To monitor the sterile and wild male populations, we placed 5 male bucket traps baited with methyl eugenol, the male attractant, and pest strips containing insecticide. The traps were placed around the field within the 4 fruit host areas- pomelo, lime, tangerine and orange and were serviced every 2 weeks. We observed an increasing sterile:wild (S:W) fly ratio during the course of the test, rising from less than 1:1 to ca. 30:1 in the last month. The level of fly control was measured by periodic (monthly) collections of host fruit from the treated field from which wild oriental fruit fly eggs were dissected and scored for hatch. The level of egg sterility provided a direct measure of induced sterility caused by the sterile males released. We observed a high initial level of sterility (35%) likely an anomaly due to the intensive male annihilation effort that was conducted for several months immediately prior to our sterile fly study. Normal control egg hatch in non-SIT areas was noted to be ca. 90%. Egg sterility rose to a level 60-70% over the remainder of the experiment, for S:W ratios as low as 2:1 to 30:1. This suggests that the sterile males succeeded quickly in sterilizing the most of the resident virgin females; but, understandably, were unable to affect a likely constant influx of mated females that migrated into the orchard from outside host areas.