Improvement of the Mass-Rearing Protocols for the South American Fruit Fly for Application of the Sterile Insect Technique

The existing rearing protocols for Anastrepha fraterculus must be reviewed to make economically viable the production of sterile flies for their area-wide application. Additionally, evidence of sexual incompatibility between a long-term mass-reared Brazilian strain and wild populations has been found. To address these issues, this study aimed to refine rearing protocols and to assess the suitability of an A. fraterculus strain for the mass production of sterile flies. A series of bioassays were carried out to evaluate incubation times for eggs in a bubbling bath and to assess the temporal variation of egg production from ovipositing cages at different adult densities. A novel larval diet containing carrageenan was also evaluated. Egg incubation times higher than 48 h in water at 25 °C showed reduced larval and pupal yields. Based on egg production and hatchability, the density of 0.3 flies/cm2 can be recommended for adult cages. The diet with carrageenan was suitable for mass production at egg-seeding densities between 1.0 and 1.5 mL of eggs/kg of diet, providing higher insect yields than a corn-based diet from Embrapa. Even after two years of being reared under the new rearing protocols, no sexual isolation was found between the bisexual strain and wild flies.

Anastrepha fraterculus (South American fruit fly).

A. fraterculus has a broad host range, particularly in the family Myrtaceae, but it is also a pest of citrus and apples [Malus domestica] in some areas. It is the most important pest species of Anastrepha in subtropical areas of South America, thus it and Anastrepha ludens may be more of a threat of introduction to other subtropical areas of the world than other species of Anastrepha. It is invasive in the Galapagos Islands. As it is probably a complex of cryptic species whose ranges and delimitation remain unresolved, there is also the threat of introduction of particular cryptic species to other areas within the range of the complex. It is considered an A1 quarantine pest by EPPO.

Determining the Sterilization Doses under Hypoxia for the Novel Black Pupae Genetic Sexing Strain of Anastrepha fraterculus (Diptera, Tephritidae)

A common strategy used to maintain sterile fly quality without sacrificing sterility is to irradiate the insects under an oxygen-reduced atmosphere. So far, sterilizing doses for the South American fruit fly Anastrepha fraterculus have only been determined under normoxia. Our study reports for the first time the dose-sterility response under hypoxia for two different A. fraterculus strains. The pupae were derived from a bisexual strain (a Brazilian-1 population) and a recently developed genetic sexing strain (GSS-89). Two hours prior to irradiation, pupae were transferred to sealed glass bottles and irradiated when oxygen concentration was below 3%. Four types of crosses with nonirradiated flies of the bisexual strain were set to assess sterility for each radiation dose. For males from both strains, Weibull dose–response curves between radiation doses and the proportion of egg hatch, egg-to-pupa recovery, and recovery of adults were determined. The GSS males revealed high sterility/mortality levels compared to males from the bisexual strain at doses < 40 Gy, but a dose of 74 Gy reduced egg hatch by 99% regardless of the male strain and was considered the sterilizing dose. The fertility of irradiated females was severely affected even at low doses under hypoxia.

Use of toxic bait to manage the south american fruit fly in apple orchards in Southern Brazil

Anastrepha fraterculus the South American fruit fly, is an important insect pest in apple orchards of southern Brazil, especially in small farms, where it often causes total crop loss. Experiments were conducted to evaluate, during four crop seasons (2009/2010, 2010/2011, 2012/2013, and 2013/2014) in organic and conventional apple orchards in southern Brazil, the toxic bait formulation ANAMED™ (oils and waxes 49.0% + M7 attractant 24.2% + spinosad insecticide 0.1%) for its capacity to reduce the South American fruit fly population. ANAMED applications started after apples with an average diameter of 20 mm had been thinned, and they were made every 14 days until harvest. ANAMED was sprayed on non-crop vegetation growing on the edges of the orchards at a rate of 1.0 kg.ha-1. Adult fruit flies were monitored weekly using McPhail traps baited with Torula™ yeast. Injured fruits were evaluated seven days before harvest. ANAMED reduced the adult population of trapped fruit flies captured in all crop seasons and the injured fruit, except for the first year of evaluation (2009/2010). In conclusion, the sequential use of ANAMED toxic bait over time significantly reduced adult populations of A. fraterculus and the percentage of fruits injured by this pest.

Identification and in situ hybridization to mitotic chromosomes of a molecular marker linked to maleness in Anastrepha fraterculus (Wied.)

The present report shows the molecular identification, isolation and citologically localization of a DNA-sequence from the South American fruit fly Anastrepha fraterculus (DIPTERA: Tephritidae) involved in sex- determination. It belongs to the Tephritidae family, the true fruit flies which are consider a pest of fruit crops. The sex determination system is of vital importance in the genetic control of the fruit fly pest: Sterile Insect Technique which unlike chemical control tactics, is environmentally friendly and does not pose any health concerns. We used in situ hybridization on mitotic chromosomes for localizing the primary sex determination factor in this fruit fly pest. Our results show that in Anastrepha fraterculus the Y chromosome is responsible for sex determination

Larvicidal and Adulticidal Activities of Neem Oil against Anastrepha fraterculus (Wied.) (Tephritidae)

In the laboratory, a neem oil-based formulation was evaluated for its insecticidal potential against the South American fruit fly Anastrepha fraterculus (Wied.), as efficient alternative for growers harvest fruits more harmless for the human consumption. The commercial product was evaluated against eggs in vitro, guavas infested with eggs and young larvae, and adults. The application of 0.8% neem oil significantly reduced the larval hatching of A. fraterculus. Neem oil at 0.4, 0.6 and 0.8% significantly reduced the number of pupae and adults per fruit infested with eggs. Guava infested with A. fraterculus eggs and treated with neem oil at 0.8% exhibited a reduction of 90.0% and 92.6% of pupae and adults per fruit, respectively. The same dosage to guava infested by larvae achieved a 44.6 and 51.4% reduction of pupae and larvae, respectively. At 360 minutes after treatment, 0.8% of neem oil provided 67.9% of corrected adult mortality. This double insecticidal effect of neem oil and lack of phytotoxicity in ripe guavas at the tested concentrations demonstrate its potential in biorational management.

Symbionts do not affect the mating incompatibility between the Brazilian-1 and Peruvian morphotypes of the Anastrepha fraterculus cryptic species complex

The South American fruit fly, Anastrepha fraterculus, is clearly undergoing a speciation process. Among others, two of their morphotypes, the Brazilian-1 and Peruvian, have accumulated differences in pre- and post-zygotic mechanisms resulting in a degree of reproductive isolation. Both harbor a different strain of Wolbachia, which is a widespread endosymbiotic bacterium among many invertebrates producing a range of reproductive effects. In this paper, we studied the role of this bacterium as one of the factors involved in such isolation process. Infected and cured laboratory colonies were used to test pre- and post-zygotic effects, with special emphasis in uni- and bi-directional cytoplasmic incompatibility (CI). We showed that Wolbachia is the only known reproductive symbiont present in these morphotypes. Wolbachia reduced the ability for embryonic development in crosses involving cured females and infected males within each morphotype (uni-directional CI). This inhibition showed to be more effective in the Peruvian morphotype. Bi-directional CI was not evidenced, suggesting the presence of compatible Wolbachia strains. We conclude that Wolbachia is not directly involved in the speciation process of these morphotypes. Other mechanisms rather than CI should be explored in order to explain the reduced mating compatibility between the Brazilian-1 and Peruvian morphotypes.