Parasitoid Fopius Arisanus Research Articles

Mortality by parasitization in the association between the egg-pupal parasitoid Fopius arisanus and Ceratitis capitata

We studied the interaction betweenthe egg-pupal parasitoid Fopius (+ Biosteres) arisanus (Sonan) (+Opius oophilus Fullaway) (Hymenoptera: Braconidae) and Ceratitis capitata (Wiedemann)(Diptera: Tephritidae) to assess the totalimpact of the parasitoid on the survival ofthis host. We tried to discover the factorsdetermining host suitability, measure actualpercent parasitism, and quantify host mortalityby parasitization. Research was carried outapplying dechorionation treatment, anon-destructive procedure that makes hosteggshells transparent to microscopicobservation, without interfering withdevelopment. We found that percent parasitismobserved at the egg stage did not correspond tothat detectable for emerging adults. In fact,parasitized host eggs were subject to a highermortality than non-parasitized ones. Moreover,a certain percentage of the parasitoid eggs didnot develop to the adult stage. Results fromour study allowed us to measure the percentmortality by parasitization per parasitizedegg. Furthermore, we analyzed the mortalityfactors due to parasitization acting during thehost egg stage. Most of them had never beenevidenced before and may help to explain thisphenomenon. In particular, we found that theage of the host eggs exposed to parasitoidsplays a fundamental role in the mortality byparasitization and that F. arisanusparasitizes C. capitata eggs moreefficiently close to the time of eclosion.

Oviposition response and development of the egg‐pupal parasitoid Fopius arisanus on Bactrocera oleae, a tephritid fruit fly pest of olive in the Mediterranean basin

AbstractTo date, information is wanting with regard to the use of new exotic parasitoids against olive fruit fly, Bactrocera (=Dacus) oleae (Gmelin) (Diptera: Tephritidae), a serious pest of olives Olea europaea L., in the Mediterranean basin. We investigated the oviposition response and developmental biology on B. oleae of Fopius (=Biosteres) arisanus (Sonan) (=Opius oophilus Fullaway) (Hymenoptera: Braconidae), an egg‐pupal parasitoid of tephritid fruit flies, never tested before as a potential parasitoid of this host. Our results showed that olive fruits infested with B. oleae eggs exerted a relevant attraction to gravid F. arisanus and represented a stimulus for oviposition. Nevertheless they were not as attractive to female parasitoids as the Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae), eggs infested papaya fruits (Carica papaya L.). In our experimental conditions, F. arisanus completed development in B. oleae within 33 ± 1.7 days (males) and 35 ± 1.6 (females). Increases in host egg to female parasitoid ratios of 1:1, 5:1, 10:1 and 20:1 corresponded with decreases in the percentage of B. oleae parasitisation and host killing but corresponded also with increases in absolute parasitisation. Our findings are discussed in light of possibilities of utilising F. arisanus for biological control of olive fruit fly.

The fruit fly parasitoid Fopius arisanus: reproductive attributes of pre‐released females and the use of added sugar as a potential food supplement in the field

Abstract Fopius (= Biosteres) arisanus (Sonan) (=Opius oophilus Fullaway) (Hymenoptera: Braconidae) is an egg‐pupal parasitoid of tephritid fruit flies. Small scale releases of F. arisanus were undertaken in coffee, Coffea arabica L., on the island of Kauai, to evaluate its potential for suppression of fruit fly populations. In conjunction with field releases, assays were conducted to determine the quality of pre‐released parasitoids. In addition, the suitability of various sugars as potential food supplements in the field was evaluated. Spermathecal dissection showed that >70% of a total 1.7 million females released in 1998 and 1999 were successfully mated. Moreover, a sperm rating of 2.5–2.6 indicated that the spermathecae of inseminated females were 50% full. There were 85–137 matured eggs (mean = 101.7 ± 11.5) in the ovaries of mated or virgin females. When honey was replaced with ripe coffee and water, ripe coffee, or water alone, 10 days after emergence, females remained alive for another 5.5, 5.4, and 4.9 days, respectively. There was corresponding deterioration in the ovaries of gravid females. Mean eggs of honey‐deprived females declined from >100 to <70 shortly before their death. Suitability test of various sugars showed that females lived longer when fed with honey (26 days), maple syrup (25 days) or molasses (20 days). Moreover, females provided with these sugars produced mean cumulative progeny per female of 77.2 ± 19, 67 ± 7, and 81 ± 14, respectively, during a 2‐week egging period. Our findings provided a basis for development of field release strategy for F. arisanus.

Host preference and host suitability in an egg‐pupal fruit fly parasitoid, Fopius arisanus (Sonan) (Hym., Braconidae)

The relative oviposition rate of the parasitoid Fopius arisanus (Sonan) was investigated across three frugivorous tephritid species, Bactrocera tryoni Froggart, Bactrocera jarvisi (Tryon) and Bactrocera cucumis French. Choice and no‐choice tests were both used. The suitability of these three species for sustaining larval development and survival to the adult stage was also assessed. Fopius arisanus parasitized all three tephritid species, regardless of the method of exposure, but showed stronger preference for B. tryoni and B. jarvisi over B. cucumis. Superparasitism was extremely rare. Successful development of F. arisanus varied across host species. Bactrocera tryoni yielded significantly more parasitoids than B. jarvisi, but no wasps emerged from B. cucumis puparia. Tests were set up in replicated trials, but results were not homogeneous across trials. We discuss the host relationships of F. arisanus with reference to this variation and in relation to host suitability for larval development.