Olive Fruit Fly, Bactrocera oleae (Diptera: Tephritidae), Attraction to Volatile Compounds Produced by Host and Insect-Associated Yeast Strains

Abstract

The olive fruit fly, Bactrocera oleae (Rossi), is one of the most damaging insect pests of olives worldwide, requiring the use of insecticides for fruit protection in many orchards. Olive fruit flies are attracted to volatile composunds, including a female-produced pheromone, and host-plant and bacterial volatiles. Preliminary laboratory bioassays were conducted for olive fruit fly attraction to over 130 yeast strains from among 400 that were isolated from B. oleae adults and larvae or other insects, infested olives, and potential feeding sites. Kuraishia capsulata, Scheffersomyces ergatensis, Peterozyma xylosa, Wickerhamomyces subpelliculosus, and Lachancea thermotolerans appeared to attract B. oleae as well or better than did torula yeast pellets (Cyberlindnera jadinii; syn. Candida utilis). Volatile compounds emitted by these yeast strains were chemically identified, and included isobutanol, isoamyl alcohol, 2-phenethyl alcohol, isobutyl acetate, and 2-phenethyl acetate. The behavioral response of B. oleae adults to these volatile compounds at three concentrations was tested in a laboratory Y-tube olfactometer. The same volatile compounds were also tested in the field. Isoamyl alcohol was more attractive than the other compounds tested in both laboratory and field bioassays. Isobutanol was not attractive to B. oleae in either laboratory bioassay or field bioassay. Identifying yeast volatiles attractive to the olive fruit fly may lead to development of a more effective lure for detection, monitoring, and possibly control of B. oleae.

Yeasts Associated with the Olive Fruit Fly Bactrocera oleae (Rossi) (Diptera: Tephritidae) Lead to New Attractants

“…In an earlier field study [33], we evaluated 12 yeast strains as active yeasts formulations for B. oleae attraction and found that certain yeast strains were more attractive than others. Five of them were significantly more attractive to B. oleae than the torula yeast pellets (Figure 2).…”

“…Twelve yeast strains from a preliminary screening of over 130 insect-associated yeast strains that showed promise for attracting B. oleae [33] were selected for field testing (Table 1).…”

“…Over 400 yeasts were isolated from infested olives, adult flies, and potential feeding sites during preliminary studies [33]. Of these yeasts, over 130 insect-associated strains showed promise for attracting B. oleae as well or better than the industry standard torula yeast pellet.…”

“…Burrack et al [36] found that commercial torula yeast pellets were more effective for attracting olive fruit flies in the field than other attractants, such as lures based on ammonia or pheromones. In our previous study [33], we found that volatiles produced by active torula yeast formulation in potato dextrose broth (PDB) differed greatly from those produced by an inactive commercial pellet of the same yeast species suspended in water. However, from a practical standpoint, the commercialization of yeast for the attraction of tephritid fruit flies is much more easily accomplished with the dry, inactive form of yeast than for active, living cultures [33].…”

“…In our previous study [33], we found that volatiles produced by active torula yeast formulation in potato dextrose broth (PDB) differed greatly from those produced by an inactive commercial pellet of the same yeast species suspended in water. However, from a practical standpoint, the commercialization of yeast for the attraction of tephritid fruit flies is much more easily accomplished with the dry, inactive form of yeast than for active, living cultures [33]. Therefore, the five most attractive yeast species, as found here through testing, were also tested as water suspensions of their non-living freeze-dried residue as a step toward advancing a more commercially-acceptable form that could be used for B. oleae detection and monitoring.…”