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item Robacker, David
item Fraser, Ivich

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2003
Publication Date: 5/15/2003
Citation: Robacker, D.C., Fraser, I. 2003. Relative attractiveness of oranges and grapefruits to mexican fruit flies (diptera: tephritidae) in a wind tunnel. Journal of Entomological Science. 38(4):566-575.

Interpretive Summary: Mexican fruit flies lay their eggs into citrus, mangoes and other fruits making them one of the most important tropical fruit pests in North America. While infested fruit loses most of its market value, a bigger problem is that fruit cannot be exported from infested production areas to many markets around the world where flies exiting infested fruit could become established and compromise fruit industries in those places. Industry and government agencies have requested studies of how this insect chooses its hosts in the hope that increased understanding of its biology may lead to more effective control and eradication programs. In this study, we wanted to determine if female flies prefer grapefruit to oranges as suggested by well-documented reports that grapefruit orchards usually suffer higher infestation and damage than orange orchards. We found that grapefruis are not more attractive to females than oranges and are not preferred over oranges for oviposition. This indicates that heavier infestations of grapefruit compared with orange orchards is not caused by greater attractiveness of grapefruits, but probably by suitability of the fruit to growing maggots, cultural practices used in orchard management, or environmental factors. Other results demonstrated that females with experience with grapefruits preferred grapefruits to oranges and those with experience with oranges preferred oranges. Moreover, flies that never experienced either fruit were not attracted to either fruit. These results indicate that Mexican fruit flies are not attracted instinctively to either of these fruits, but must learn they are suitable hosts. This suggests that removing fruit from orchards during the off-season may reduce future infestations by preventing young inexperienced flies from learning these fruits are hosts. These studies show that simple cultural practices could have major impacts on infestation of citrus orchards by fruit flies.

Technical Abstract: Grapefruits and sweet oranges were equally attractive and elicited similar oviposition behavior from native, oviposition-ready, laboratory-strain female Mexican fruit flies (Anastrepha ludens Loew). Naïve wild females were attracted equally to grapefruits, oranges, and yellow plastic balls. For lab females, experience with grapefruit enhanced attraction only to grapefruits, but experience with oranges enhanced attraction to both fruits. For wild females, experience with grapefruit enhanced attraction to both fruits and experience with oranges enhanced attraction at least to oranges. In general, experience with a fruit increased response moreso to the experienced fruit than to the other. Experience with oranges, but not grapefruits, also enhanced attraction of wild females to plastic yellow balls of similar size to oranges, indicating that flies were learning to recognize fruit by its size moreso than its color. Other results showed that naïve lab females, but not wild females, were attracted to both host fruits; experience with fruit decreased oviposition behavior directed toward wind-tunnel walls; laboratory males were attracted to both fruits, but wild males were attracted to neither; and experience with fruit had very little effect on behavior of males. Our results do not explain reported host preference for grapefruits over oranges by Mexican fruit flies.