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Title: Host status of Meyer and Eureka lemons for Anastrepha A. ludens (Loew)

item Mangan, Robert
item Tarshis Moreno, Aleena

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/2011
Publication Date: 4/20/2012
Citation: Mangan, R.L., Tarshis Moreno, A.M. 2012. Host status of Meyer and Eureka lemons for Anastrepha A. ludens (Loew). Journal of Economic Entomology. 105:363-370.

Interpretive Summary: Smooth skinned lemons, such as the Eureka cultivar, are not hosts for the Mexican fruit fly for early to midseason harvested fruit. Fruit harvested from regions where these flies are established or when outbreaks of these flies occur, may be shipped to fly free areas without quarantine treatment for commercial maturity fruit. Meyer lemon is a hybrid cultivar thought to be from lemon x orange or lemon x mandarin. Meyer lemons are listed as hosts for several fruit fly species, but not as a host for the Mexican fruit fly. Tests were performed to compare Eureka and Meyer lemons as hosts for this pest. Tree blossoming and fruit set were coordinated so that fruit were approximately the same maturity. Fruit were harvested over the early to late season (September to March) period in 2008 and 2009 to compare host status over the maturity cycle. Fruit were harvested and infested in laboratory cages with fruit wrapped to expose a small (2.5 cm diameter) hole for oviposition. Fruit were then held in covered trays until larvae matured and fruit were dissected. Eggs were deposited into both the albedo (white inner peel tissue) and pulp for both cultivars. Eureka lemons had very low survival of larvae in the September to December harvests (early to midseason) and did not produce pupae or adults until very late season. Meyer lemons produced some mature larvae and adults from early through late mature stages. Physical and chemical characteristics of the fruit, such as color and sugar content were related to maturity, but only weakly related to larval survival to produce pupae and adults. Since Meyer lemons produced mature larvae, pupae and adults over the very early to late maturity stages and greater numbers of survivors through the larval stages, we rated Meyer lemons as a host at all maturities. Eureka lemons were rated as hosts only at maturities which would not be marketable.

Technical Abstract: Host status for Mexican fruit fly Anastrepha ludens (Loew) was examined under laboratory conditions in cage infested Eureka and Meyer lemons. Our approach was to allow females to oviposit on the two cultivars in separate laboratory cages with aluminum foil covering to restrict the areas where females had access to fruit surface. Fruit of each cultivar were placed in covered trays for incubation and at approximately weekly intervals, fruit were removed and dissected. Larvae and live/dead eggs were tabulated in each tissue of the fruit. Infestation and survival rates were tabulated/analyzed for the effects of harvest date, fruit color, and briz indices, post-oviposition period, and cultivar. Infestation rate, determined by counts of total eggs and larvae, was significantly higher in Meyer lemons. In both cultivars, females deposited eggs into both albedo and pulp tissue, but not into flavedo. Both cultivars showed high resistance (greater than 90 percent mortality) to egg and first instar survival in albedo and pulp. Second and third instars surviving in the pulp had high survival rates (greater than 60 percent) in both cultivars in fruit dissected at weeks 2-4 after infestation. Total adults produced were slightly higher and total second/third stage larvae were also higher for Meyer lemons. Numbers of adults and total second/third stage larvae increased in Eureka lemons in more mature fruit, but the higher numbers in Meyer lemons were not associated with fruit maturity, at time of infestation. Numbers of second/third stage larvae were significantly correlated with some fruit color indices in Eureka, but not in Meyer lemons. Application of these results to quarantine risk analysis is discussed.