DEVELOPMENT OF QUARANTINE ALTERNATIVES FOR SUBTROPICAL FRUIT AND VEGETABLE PESTS
Title: Host status of grapefruit and Valencia oranges for Anastrepha serpentina and Anastrepha ludens
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 7, 2010
Publication Date: April 1, 2011
Citation: Mangan, R.L., Thomas, D.B., Tarshis Moreno, A.M. 2011. Host status of grapefruit and Valencia oranges for Anastrepha serpentina and Anastrepha ludens. Journal of Economic Entomology. 104(2):388-397.
Interpretive Summary: The fruit fly, Anastrepha serpentina, commonly called the sapote fly or the serpentine fruit fly, is occasionally captured in subtropical areas in Texas and California. In Texas, most years (from 1994-2009) we had trappings of zero to one or two flies per year, with one outbreak year of ten flies. The host plant list for this species includes several citrus species, so regulatory actions are required when this species is captured in citrus growing regions of the United States. In this paper, we tested la coma as a host and discovered that females could infest, and eggs hatched and produced adults in this species. The host status of citrus was tested with A. serpentine and the known citrus pest, A. ludens, the Mexican fruit fly. Laboratory infestations of restricted area caged fruit were made, then the fruit was dissected at weekly intervals to determine the developmental stage and survival rates in the various tissues. Rio Red grapefruit and Valencia oranges were tested. In both fruit, all inserted eggs for either fruit fly species were deposited in the white tissue (albedo) below the oil glands. Mortality of eggs not hatching to produce larvae was over 90% in A. serpentine and between 40-60% for A. ludens. Larval mortality for both species was also quite high in the albedo. However, in all fruit samples with larvae surviving and entering the pulp tissues, very few dead larvae were found and there was survival of eggs to pupate and form adults. In grapefruit, there was some survival to adults in all stages of commercially mature fruit. Survival to adult stage was much greater for A. ludens in oranges, but no A. serpentine larvae survived to enter the pulp or produced adults. These developmental data suggest that citrus fruit have much higher resistance compared to A. ludens. The historical data for A. serpentina indicate that only one infestation was found when populations of A. serpentina in commercial orchards were thousands of times greater than present trapping records. The observed resistance and historical paucity of infestations under very high populations suggest that a quarantine system should be based on this host resistance and preference in the field.
Anastrepha serpentina, known as the zapote fly or serpentine fruit fly, is occasionally captured in the Rio Grande Valley of Texas. Lists of host plants for this species include several species of citrus, such as oranges and grapefruit. Current regulatory procedures require quarantines and treatments for all commercial citrus in an outbreak area following captures of A. serpentine. Citrus host reports from North/Central America and the history of A. serpentine populations in northern Mexico and Texas were used as references. Citrus field infestations include one report from grapefruit in Texas in 1934, one report from sweet and sour oranges from Chiapas in 1987, and one report of several field infestations from Panama in the early 1930s. Tests were performed with la coma, a native species of Sapotaceae and la coma (Siderxylon celastrinum) with A. serpentine, which successfully oviposited into berries on the plants, and normal adults developed. Our research study evaluated the host status of commercial citrus for A. serpentina and we tested oviposition and development of this species and A. ludens under laboratory conditions. Both species showed oviposition behavior typical of polyphagous (multiple hosts) species. Both species oviposited in early season fruits in which all eggs and larvae died in the albedo of the fruit. In oranges, both species dumped eggs on the surface of the fruit, also a characteristic of polyphagous species. Survival on both citrus species was much lower for A. serpentine, only about 5% of eggs of A. serpentina eclosed into larvae in grapefruit compared to about 50% for A. ludens. In oranges, about 16% of A. serpentine eggs eclosed compared to about 76% for A. ludens. In grapefruit, 23 A. serpentine survived to adult stage compared to 104 A. ludens. In oranges, no A. serpentine larvae survived in the albedo, but 150 A. ludens survived to form adults. Population densities of A. serpentine were at least 500 times greater in the 1930s when the grapefruit infestation in Texas was reported than present populations. This, coupled with the high mortality during development in the albedo, suggests that Valencia oranges and Rio Red grapefruit are unlikely to allow survival of adults under current population levels.