No Sting in the Tail for Sterile Bisex Queensland Fruit Fly (Bactrocera tryoni Froggatt) Release Programs

SIMPLE SUMMARY: Fruit fly (Tephritidae) present a global market-access issue for horticultural produce. A key method of control for tephritidae pests is the sterile insect technique (SIT). Australia has released a bisex strain, i.e., males and females of sterile Queensland fruit fly, Bactrocera tryoni Froggatt, although only the males contribute to wild-population decline. While the number of stings were higher in one SIT release orchard, compared with the control, we showed that sterile female B. tryoni released in large numbers do not lead to degraded or unmarketable fruit, and therefore are suitable for release in commercial nectarine, peach and plum orchards. ABSTRACT: Global markets do not tolerate the presence of fruit fly (Tephritidae) in horticultural produce. A key method of control for tephritidae pests, is the sterile insect technique (SIT). Several countries release a bisex strain, i.e., males and females, however the sterile male is the only sex which contributes to wild population declines when released en masse. In commercial orchards, there are concerns that sterile females released as part of bisex strains, may oviposit, i.e., ‘sting’ and cause damage to fruit, rendering it unmarketable. Australia has released a bisex strain of sterile Queensland fruit fly, Bactrocera tryoni Froggatt, for several decades to suppress wild pest populations, particularly in peri-urban and urban environments. Here, we assessed fruit damage in two commercially grown stone fruit orchards where bisex sterile B. tryoni were released, and in an orchard that did not receive sterile flies. The number of detected stings were higher in only one SIT release orchard, compared with the control; however, there was no difference between SIT and control orchards in the number of larvae detected. We showed that there is no evidence that sterile female B. tryoni released in large numbers caused stings, or damage that led to downgraded or unsaleable fruit. The bisex strain of sterile B. tryoni is recommended for use in commercial stone-fruit orchards, under the conditions in which this trial was conducted.