Bactrocera tryoni (Froggatt, 1897)

Queensland fruit fly  

General

• Insect of the Tephritidae family native to Queensland on the east coast of Australia. Arrived in New Caledonia at the end of the sixties.
• In New Caledonia, it is capable of carrying out its development cycle on more than 50 cultivated or wild plant species.
• Particularly damaging in fruit growing, this fly parasitizes Solanaceae in particular, as well as strawberries on which the damage can be substantial.
• It is one of the most economically impactful fruit fly species in the world.
• Observed in the open field as well as under shelters.

• Sensitive botanical family (s)

* cultivated : tomato, pepper in particular, eggplant and pepper.

• Affected production areas :

• Organs attacked

 Symptoms, damage

• Symptoms :
  • More or less punctiform lesions on the fruits corresponding to fly bites; recent bites are often quite discreet.
  • Extension of the puncture zone which darkens and often evolves into rot gradually spreading to all the fruits, this as the activity of the maggots progresses. Note the possible presence of Drosphyla maggots ( Drosophila spp. ) as opportunistic invaders.

• Signs : Presence of flies and larvae on and in the affected organs, and in the culture (figures ).
• Possible confusion : This fruit fly could be confused with Bactrocera dorsalis which is currently absent from New Caledonia.

 Biology

• Biological cycle : The female lays her eggs under the skin of the host fruit a few millimeters deep thanks to her pointed ovipositor.
  • The eggs hatch in 1 to 3 days.
  • The larvae feed in the bitten fruits for about twenty days, the time to complete 3 successive larval stages.
  • At the end of the third larval stage, the larva extracts itself from the fruit to fall to the ground and pupate underground at the foot of the host plant.
  • Les adultes émergent enfin après 1 à 2 semaines, ils mesurent 6 à 7 millimètres. De couleur brun clair, ils sont identifiables grâce au trait jaune longitudinal présent de chaque côté de l’abdomen, et de leur scutellum (partie postérieure du thorax) entièrement jaune vif. Les bandes présentes le long des marges internes et externes des ailes complètent leur identification.
• Le cycle d’œuf à œuf de cette espèce est d’environ 40 jours. La durée du cycle diminue avec l’augmentation des températures. B. tryoni est présente tout au long de l’année, avec un pic d’activité de février à mai et des populations beaucoup moins importantes entre juin et octobre. Les niveaux de population dépendent à la fois des variations de température et de la disponibilité en nourriture dans l’environnement immédiat de la parcelle.

 Protection

• The strategy for combating this fruit fly revolves around three complementary areas of intervention:
  • Mass trapping (MAT: Male Attractant Technique): this trapping is done using cuelure (sex pheromone attracting males) and placing traps at a rate of 25 traps per hectare (1 every 20 meters). It must be carried out continuously throughout the year.
  • Collecting and placing in an augmentorium (1) bitten fruits and fruits on the ground in order to limit access to food for adult insects, but also to promote the maintenance of naturally present fruit fly parasitoids.
  • Spot treatment triggered when the impact on the crop becomes too great. This consists of spraying a food attractant associated with an insecticide on 1 m² of surface every 20 m. The treatment can be carried out on canvas, portions of hessian or on grassy parts within the plot.

• A count every 15 days on a few control traps makes it possible to follow the evolution of population levels over time and to better manage the triggering of treatments by tasks.

(1) Structure resembling a closed tent in which infested fruits collected in the field are regularly placed. The augmentorium thus prevents the re-infestation of the agroecosystem by a new generation of adult flies that emerge in the augmentorium, while a net with an appropriate mesh, placed on the roof of the augmentorium, makes it possible to release fly parasitoids into the wild.