Parasitoids of Fruit-Infesting Tephritidae

For additional information, see the Diachasmimorpha page.

This species was originally described by Cameron (1911) as Opius tryoni. In older literature, the generic names most commonly used for this species are Opius, Diachasma, and Biosteres . Wharton and Gilstrap (1983), for example, used the combination Biosteres tryoni and Clausen et al. (1965) used the combination Opius tryoni . However, Silvestri (1914), when he introduced this species from Australia to Hawaii, called it Diachasma tryoni as did Pemberton and Willard (1918), who published one of the most detailed and earliest studies on it’s biology. Fischer (1987) has also used the name Parasteres tryoni . Wharton 1987 transferred this species to Diachasmimorpha.

Biosteres acidusae Fischer, 1967 is a synonym of tryoni (Wharton and Marsh 1978, Wharton and Gilstrap 1983).

Diachasmimorpha tryoni has an apically sinuate ovipositor (Fig. 4) and deeply impressed notauli, but no striae on the second metasomal tergum (Fig. 1). Unlike the majority of the species now placed in Diachasmimorpha, the occipital carina of D. tryoni is absent or nearly so (sometimes represented by a very short ridge near the base of the mandible).

Native to eastern Australia (see Carmichael et al. 2005).

Introduced to Hawaii, Florida, California, and several places in Latin America but in most places outside Hawaii, either failed to establish or establishment has not been confirmed. Guatemala is a relatively recent exception.

Detailed biologies of this parasitoid have been published, beginning with the careful studies of Pemberton and Willard (1918a, 1918b). More recently, Ramadan et al. (1989), Wong et al. (1990), and Messing et al. (1993) examined such features as realized fecundity and the influence of cohort age and host age on offspring sex ratio as a prelude to work on developing a mass rearing program for inundative releases using this species (Ramadan et al. 1989, Wong et al. 1991, Wong et al. 1992, Messing et al. 1994, Sivinski et al. 2000). Hurtrel et al. described the development time and temperature thresholds for Diachasmimorpha tryoni (Cameron) in Ceratitis capitata (Hurtrel et al. 2001) when this species was introduced to the island of La Reunion. They found that D. tryoni can develop within the temperature range of 15°C to 28°C, with development times of 63.60 and 16.52 days respectively. At the lower end of the temperature range they found the sex ratio to be heavily male-biased. Vargas et al. (2002) published useful studies on comparative demography of this and other species introduced to Hawaii.

The first records of Diachasmimorpha tryoni were apparently by Gurney (1910), (1911) in Australia who noted that it developed on both the native host, Queensland fruit fly, as well as the introduced pest Mediterranean fruit fly. May and Kleinschmidt (1954) placed D. tryoni in perspective relative to other opiine parasitoids of Tephritidae in Queensland. Jessup and Walsh (1998) examined diapause in lab cultures that had been recently collected in New South Wales.

Diachasmimorpha tryoni has been reared from gall-making tephritids, though uncommonly (Bess and Haramoto 1958, Bess and Haramoto 1972, Duan and Messing, 1996, Duan et al. 2000). In an experiment to address the issue of nontarget host impacts of introduced fruit fly parastoids, Duan et al. found that D. tryoni and D. longicaudata (Ashmead) were able to successfully recognize the host plant of the the gall forming tephritid Eutreta xanthochaeta Aldrich and parasitize the fly larvae within an experimental setting (Duan et al. 1997, Duan and Messing 1999). Eutreta xanthochaeta, a nontarget host of the opiine parasitoids, was introduced to Hawaii to control lantana in 1902. The success rate for locating the infested lantana in a natural field setting for these parasitoids is not known. Duan and Messing (2000) also looked at attack of flower-infesting tephritids in experimental cage settings.

In interspecific competition studies with Fopius arisanus (Sonan), a tephritid egg-prepupal parasitoid, Wang and Messing (2003), found that D. tryoni rarely survived in hosts previously parasitized by F. arisanus. The authors suggest that competition from F. arisanus in regions of Hawaii where both parasitoids have been introduced may be driving D. tryoni to select nontarget host species. Earlier work (summarized in Willard and Mason 1937) showed effect of competitive displacement between Psyttalia humilis and D. tryoni, with both operating effectively in preferred habitats/seasons.

This species does not develop on Oriental fruit fly unless the latter has previously been attacked by another parasitoid.

Diachasmimorpha tryoni is one of the most important species used in tephritid biocontrol programs to date. It has been introduced to Hawaii, Florida, Latin America, and elsewhere, where it attacks fruit-infesting tephritids in other genera such as Anastrepha Schiner and Ceratitis MacLeay. Early efforts even included movement of individuals within Australia from areas where it was abundant to areas where it was not (Jarvis 1922).

Originally introduced to Hawaii by Silvestri in 1913 to control Ceratitis capitata, the medfly (Back and Pemberton 1915, Pemberton and Willard 1918, Back and Pemberton 1918, Willard and Mason 1937), this species continues to play an important role in suppression of populations of this pest in Hawaii (Wong et al. 1984, Wong and Ramadan 1987).

Methods for mass rearing this species for augmentative biological control have been published (Ramadan et al. 1989, Wong and Ramadan 1992), and production figures of over a million wasps per week have been achieved. Associated demographic work was published by Carey et al. (1988).

A listing of D. tryoni introductions in the New World for biological control is provided below summarized from Ovruski et al. (2000):

Argentina—-against Ceratitis capitata (Ovruski et al. 2003).
Puerto Rico—introduced in 1935-37 against Anastrepha suspensa, A. obliqua (Bartlett 1941).
Costa Rica—introduced in 1955 against Ceratitis capitata (Clausen 1978).
Mexico—introduced in 1988, 1994 against A. ludens.
Guatemala—introduced in 1995 against C. capitata (Sivinski et al. 2000).