Updates on the development of female attractants for improved monitoring of oviposition-impending Bactrocera dorsalis

Authors: Cha, Dong; ROH, GUANG-HYUN - US Department Of Agriculture (USDA); Kendra, Paul

Submitted to: Fruit Flies of Economic Importance International Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2022
Publication Date: 11/13/2022
Citation: Cha, D.H., Roh, G.H., Kendra, P.E. 2022. Updates on the development of female attractants for improved monitoring of oviposition-impending Bactrocera dorsalis. 11th Fruit Flies of Economic Importance International Symposium. Sydney, Australia. 13-18 Nov 2022.

Interpretive Summary:

Technical Abstract: Background: There is a clear need for a new and more potent attractant for surveillance of female oriental fruit fly (OFF). Worldwide, OFF is one of the most destructive invasive pests of fruit that can become a serious trade-barrier once established. Current OFF surveillance programs in the US rely on a large number of traps (10,000 traps/yr in CA) baited with methyl eugenol and liquid protein bait (torula yeast, TY). Although methyl eugenol is a highly potent attractant, it only attracts males and cannot monitor OFF females. TY-baited traps can attract both sexes and thus have been used for detection of female OFF. However, TY is not strong enough to meet program needs as a standard female attractant; furthermore, TY traps are difficult to maintain, attracts many non-target insects, and changes attractiveness with time. Methods: We evaluated differences in egg load and oviposition by mated female OFF that preferred host fruit odor or protein food odor. We collected headspace volatiles from a preferred host fruit (guava), then used GC-EAD and GC-MS to identify host fruit volatiles that can be detected by female OFF antennae. We evaluated the attractiveness of EAD-active compounds using laboratory bioassays and field trapping experiments. Results: The lack of suitable sensitivity of TY traps for OFF females appears to be related to its inability to attract females ready for oviposition. In bioassays using cohorts of 14~16-day old mated OFF females, some preferred traps baited with TY while some preferred traps baited with host fruit. Interestingly, the mated females that preferred host fruit odor had 2X more mature eggs in their ovaries and laid 2X more eggs than mated females that preferred TY odor, suggesting great potential for using host fruit odor-based lures to monitor “oviposition-ready” mated females and improve the efficacy of OFF detection. We identified a 16-component chemical lure that is as attractive to female OFF as a preferred host fruit and significantly more effective than TY in catching oviposition-impending females in the field. Conclusion: Our results suggest that protein-odor based OFF attractant will be preferentially more effective for unmated and not oviposition-ready mated female, while host fruit odor based lure is more sensitive to oviposition-ready mated OFF females. Thus, using both types of lures targeting OFF females with different reproductive physiological status will increase detection sensitivity of OFF females. In this talk, brief updates on other chemical ecology projects currently being conducted to develop synthetic protein based lure and oviposition deterrents for OFF.