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Biology of Selected Opiine parasitoids (Braconidae) and Their Abundance Relative to the Host, Bactrocera dorsalis (Hendel), on Carambola
Dissertation Abstract:
The opiines (Hymenoptera: Braconidae) are important parasitoids of the oriental fruit fly, Baclrocera dorsalis (Hendel) (Diptera: Tephritidae). In an attempt to exploit their potential in the integrated control of this pest, field and laboratory studies were conduted to generate information about the biology and abundance of the major species. Based on contribution to overall parasitization, the opiine parasitoides associated with B. dorsalis in star fruit could be ranked in the following order of importance: Biosteres persulcatus Silvestri, (46.53) > B. arisanus (Sonan), (32.82) > B. longicaudatus Ashmead, (15.69) > Opius fletcheri Silvestri, (4.95). Field populations of fruit fly and parasitoids had two peak periods/year, and both were significantly correlated with the abundance of their respective hosts, except B. longicaaudatus. However, their activities were significantly unaffected by size and height of host fruit in the tree.
Biological studies on three parasitoids, B. persulcatus, B. arisanus, and B. longicaudatus, showed that mating and oviposition commenced on the first day of adult emergence. Highest daily mean fecundity and number of adults produced per female occurred on the fourth day of adult life, and coincided with the peak of egg maturation. B. arisanus preferred newly laid host eggs (1-12 hour), B. persulcatus were partial to incubated eggs (24 hr), and B. longicaudatus favored older larvae (96-1 20 hr) for oviposition. The egg stages of B. arisanus, B. persulcatus and B. longicaudatus averaged 27.9, 27.0. and 53 .5 hr, respectively, and the entire developmental period of each species was one day longer for females than males (figures for males in parentheses), which were as follows: 17.3 (16.3), 17.6 (16.4), and 17. 1 (16.3 ), respectively.
Illustrations and detailed morphological descriptions were made for the different developmental stages of these three species, including their external male genitaIia.
The three parasitoids were similar in terms of gross and net lifetime fecundity: B. arisan us , 63. 19 and 36.65 eggs per female; B. longicaudatus, 60.16 and 35.48; and B. persulcatus, 56.96 and 35.38; as well as intrisic rates of increase (0.30, 0.31. and 0.31, respectively).
Since egg hatchability was unaffected by the presence of other species in multiple parasitized hosts, survival of species was determined by predation among the first-instars in the same host. B. longicaudatus prevailed over the two other species, and B. persulcatus over B. arisanus.
A II the three parasitoids were observed to superparasi tize their host. Poor effective parasitization in B. longicaudatus can be attributed to the high incidence of superparas itization and encapsulation of its eggs by the host larvae. Encapsulation was not observed on eggs of B. arisanus and B. persulcalus and superparasitization of host by these species was not as prevalent as in B. longicaudatus.
Six-day old puparia containing any of the three paras itoids could be stored at 12ºC for two weeks and still have about 50 percent adult emergence.
