White pupae phenotype of tephritids is caused by parallel mutations of a MFS transporter.

Mass releases of sterilized male insects, in the frame of sterile insect technique programs, have helped suppress insect pest populations since the 1950s. In the major horticultural pests Bactrocera dorsalis, Ceratitis capitata, and Zeugodacus cucurbitae, a key phenotype white pupae (wp) has been used for decades to selectively remove females before releases, yet the gene responsible remained unknown. Here, we use classical and modern genetic approaches to identify and functionally characterize causal wp- mutations in these distantly related fruit fly species. We find that the wp phenotype is produced by parallel mutations in a single, conserved gene. CRISPR/Cas9-mediated knockout of the wp gene leads to the rapid generation of white pupae strains in C. capitata and B. tryoni. The conserved phenotype and independent nature of wp- mutations suggest this technique can provide a generic approach to produce sexing strains in other major medical and agricultural insect pests.

Modified Atmosphere Does Not Reduce the Efficacy of Phytosanitary Irradiation Doses Recommended for Tephritid Fruit Flies.

Phytosanitary irradiation (PI) has been successfully used to disinfest fresh commodities and facilitate international agricultural trade. Critical aspects that may reduce PI efficacy must be considered to ensure the consistency and effectiveness of approved treatment schedules. One factor that can potentially reduce PI efficacy is irradiation under low oxygen conditions. This factor is particularly important because storage and packaging of horticultural commodities under low oxygen levels constitute practices widely used to preserve their quality and extend their shelf life. Hence, international organizations and regulatory agencies have considered the uncertainties regarding the efficacy of PI doses for insects infesting fresh commodities stored under low oxygen levels as a rationale for restricting PI application under modified atmosphere. Our research examines the extent to which low oxygen treatments can reduce the efficacy of phytosanitary irradiation for tephritids naturally infesting fruits. The effects of normoxia (21% O2), hypoxia (~5% O2), and severe hypoxia (< 0.5% O2) on radiation sensitivity of third instars of Anastrepha fraterculus (sensu lato), A. ludens (Loew), Bactrocera dorsalis (Hendel), and Ceratitis capitata (Wiedemann) were evaluated and compared at several gamma radiation doses. Our findings suggest that, compared to normoxia, hypoxic and severe-hypoxic conditioning before and during irradiation can increase adult emergence and contribute to advancement of larval development of tephritid fruit flies only at low radiation doses that are not used as phytosanitary treatments. With phytosanitary irradiation doses approved internationally for several tephritids, low oxygen treatments applied before and during irradiation did not increase the emergence rates of any fruit fly species evaluated, and all treated insects died as coarctate larvae. Thus, the findings of our research support a re-evaluation of restrictions related to phytosanitary irradiation application under modified atmospheres targeting tephritid fruit flies.

Relative Tolerance of Three Morphotypes of the Anastrepha fraterculus Complex (Diptera: Tephritidae) to Cold Phytosanitary Treatment.

The Anastrepha fraterculus (Wiedemann) complex is currently comprised of at least eight morphotypes, including several that are likely to be described as new species. It is critical to evaluate whether the morphotypes differ in tolerance to phytosanitary treatments. Temperatures from 0 to 3°C are used as a phytosanitary treatment for some commodities exported from the region and at risk of infestation by the A. fraterculus complex. Description of A. fraterculus morphotypes as new species could result in the annulation of phytosanitary treatment schedules for the new species. This study compared the relative cold tolerance of five populations from three morphotypes of the A. fraterculus complex: Andean, Peruvian, and Brazilian-1. Both a laboratory and wild strain of the Brazilian-1 morphotype were studied. Differences in mortality of third instars of the five A. fraterculus populations reared on nectarines were observed only with short treatment durations at temperatures ranging from 1.38 ± 0.04°C to 1.51 ± 0.08°C (mean ± SEM). Estimated times to achieve the LT99.99682 (probit 9) showed that Brazilian-1 wild, Brazilian-1 laboratory, and Cusco population were the most cold tolerant, followed by Andean and Peruvian, the least cold tolerant morphotype (i.e., Brazilian-1 wild = Brazilian-1 laboratory = Cusco population > Andean > Peruvian). These findings suggest that the current cold treatment schedules of 15 d at ≤ 1.11°C and 17 d at ≤ 1.67°C can be applied as cold treatments to any potential new species that may arise from the A. fraterculus complex.

Comparison of Populations of Ceratitis capitata (Diptera: Tephritidae) from Three Continents for Susceptibility to Cold Phytosanitary Treatment and Implications for Generic Cold Treatments.

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is arguably the most significant and studied quarantine pest of fresh fruits. There is well over a century of research observations on its response to cold, first as it pertains to shipment of fruits using cold temperatures to preserve fruit quality and how that may aid the survival and distribution of the pest, and then the use of colder temperatures to kill the pest in fruit shipments. Cold tolerance at 1.1°C in three populations of C. capitata generally increased as the insect developed; therefore, the third instar is the most tolerant of the stages that are found in fruit. The three populations did not differ in cold tolerance, indicating that cold phytosanitary treatments against this pest can be harmonized regardless of country of origin of marketed fruit hosts. This study facilitated the approval of some cold treatment schedules for the International Plant Protection Convention treatment manual that were being held up by concerns of possible differences in cold tolerance among C. capitata populations from different countries and points toward the possibility of generic, broadly applicable phytosanitary cold treatments. Most larvae found alive after 9 d of cold treatment did not pupariate and fewer still emerged as adults, indicating that acute larval mortality need not always be the objective of a cold phytosanitary treatment to be efficacious in preventing the establishment of invasive species.

Eradication of tephritid fruit fly pest populations: outcomes and prospects.

BACKGROUND: The number of insect eradication programmes is rising in response to globalisation. A database of arthropod and plant pathogen eradications covers 1050 incursion responses, with 928 eradication programmes on 299 pest and disease taxa in 104 countries (global eradication database b3.net.nz/gerda). METHODS: A subset of the database was assembled with 211 eradication or response programmes against 17 species of fruit flies (Tephritidae) in 31 countries, in order to investigate factors affecting the outcome. RESULTS: The failure rate for fruit fly eradication programmes was about 7%, with 0% for Ceratitis capitata (n = 85 programmes) and 0% for two Anastrepha species (n = 12 programmes), but 12% for 13 Bactrocera species (n = 108 programmes). A number of intended eradication programmes against long-established populations were not initiated because of cost and other considerations, or evolved during the planning phase into suppression programmes. Cost was dependent on area, ranged from $US 0.1 million to $US 240 million and averaged about $US 12 million (normalised to $US in 2012). In addition to the routine use of surveillance networks, quarantine and fruit destruction, the key tactics used in eradication programmes were male annihilation, protein bait sprays (which can attract both sexes), fruit destruction and the sterile insect technique. CONCLUSIONS: Eradication success generally required the combination of several tactics applied on an area-wide basis. Because the likelihood of eradication declines with an increase in the area infested, it pays to invest in effective surveillance networks that allow early detection and delimitation while invading populations are small, thereby greatly favouring eradication success.