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

Responses of two Anastrepha species' immature stages infesting preferential hosts to different temperature exposures

Anastrepha fraterculus (Wiedemann) and A. obliqua (Macquart) are important pests of fruit crops. In Brazil, these species cause damage to fruit growing in the South (annual average temperature of 20.9 °C) and Northeast (average yearly temperature of 24 °C). We evaluated the effect of temperature on the viability and development time of A. fraterculus and A. obliqua immature stages in their respective preferred hosts, guava (Psidium guajava L., Myrtaceae) and mango (Mangifera indica L., Anacardiaceae). The duration of egg and pupal stages, egg to pre-pupa, and viability of egg and pupal stages under different temperatures (15, 20, 25, 30, and 35 °C) were assessed. For both species, development time decreased with increasing temperature. Viability in the evaluated stages was only observed between 15 and 30 °C. However, the species responded differently to the exposure temperatures (15 and 30 °C), especially in the pupal stage and from egg to pre-pupa. Anastrepha fraterculus showed a lower tolerance to high temperatures, especially in the pupal stage and from egg to pre-pupa, which may explain its lower importance and economic impact in warmer Brazilian regions. Anastrepha obliqua had a lower tolerance at 15 °C, indicating greater adequacy for temperatures above 20 °C, characteristic of Northeast Brazil, suggesting the capacity to spread to cooler areas with rising temperatures.

The applicability of species sensitivity distributions to the development of generic doses for phytosanitary irradiation

Ionizing radiation is used as a phytosanitary treatment to prevent the introduction of pests through trade. Generic doses are a valuable means to increase the number of pest-commodity combinations that can be treated using phytosanitary irradiation. Generic doses allow for the treatment of the entire taxa for which the dose has been approved, allowing for the treatment of untested species. As such, the approval of a generic dose requires substantial supporting data and careful consideration of the risks involved. We adopt the Species Sensitivity Distribution (SSD) framework, already in widespread use in the field of ecotoxicology and environmental risk assessment, to evaluate generic doses for phytosanitary irradiation treatments. Parametric SSDs for Curculionidae and Tephritidae were developed using existing data on efficacious phytosanitary irradiation treatments. The resulting SSDs provided estimates of the taxa coverage expected by the generic dose, along with the margin of uncertainty. The SSD analysis lends support to the existing 150 Gy generic dose for Tephritidae and a proposed 175 Gy generic dose for Curculionidae. The quantitative estimates of risk produced by the SSD approach can be a valuable tool for phytosanitary rule making, improving the process for generic dose development and approval.

Phytosanitary and Technical Quality Challenges in Export Fresh Vegetables and Strategies to Compliance with Market Requirements: Case of Smallholder Snap Beans in Kenya

Kenya is one of the leading exporters of snap beans (Phaseolus vulgaris) to Europe, but the export volume has remained below potential mainly due to failure to meet the market quality standards. The quality concerns include the presence of regulated and quarantine pests, pesticide residues, harmful organisms, and noncompliance with the technical standards. These challenges call for the development of alternative approaches in overcoming the phytosanitary and quality challenges in the export of snap beans and other fresh vegetables. These may include integrated pest management (IPM) approaches that incorporate non synthetic chemical options, such as diversified cropping systems, plant and microbial-based pesticides, varieties with multiple disease and pest resistance, insecticidal soaps, pheromones and kairomones, entomopathogens and predators. These approaches, coupled with capacity-building and adherence to the set quality standards, will improve compliance with export market requirements. The aim of this paper is to increase knowledge on implementing good practices across the value chain of fresh vegetables that would lead to improved quality and thereby meeting institutional requirements for the export market. The novelty of the current review is using snap beans as a model vegetable to discuss the challenges that must be mitigated for the quest of achieving high quality and increased volume of fresh export products. Whilst many of the publications have focused on alternatives to synthetic pesticides in addressing MRLs in fresh vegetable exports, there is a disconnect between research and industry in achieving chemical residue and pest free export vegetables. This review describes the phytosanitary and technical challenges faced by smallholder farmers in accessing export markets, evaluates the phytosanitary and quality requirements by the niche markets, and explores the strategies that could be used to enhance compliance to the institutional and market requirements for fresh vegetables.

Geographic distribution of sex chromosome polymorphism in Anastrepha fraterculus sp. 1 from Argentina

BACKGROUND

Anastrepha fraterculus is recognized as a quarantine pest in several American countries. This fruit fly species is native to the American continent and distributed throughout tropical and subtropical regions. It has been reported as a complex of cryptic species, and at least eight morphotypes have been described. Only one entity of this complex, formerly named Anastrepha fraterculus sp. 1, is present in Argentina. Previous cytogenetic studies on this morphotype described the presence of sex chromosome variation identified by chromosomal size and staining patterns. In this work, we expanded the cytological study of this morphotype by analyzing laboratory strains and wild populations to provide information about the frequency and geographic distribution of these sex chromosome variants. We analyzed the mitotic metaphases of individuals from four laboratory strains and five wild populations from the main fruit-producing areas of Argentina, including the northwest (Tucumán and La Rioja), northeast (Entre Ríos and Misiones), and center (Buenos Aires) of the country.

RESULTS

In wild samples, we observed a high frequency of X1X1 (0.94) and X1Y5 (0.93) karyomorphs, whereas X1X2 and X1Y6 were exclusively found at a low frequency in Buenos Aires (0.07 and 0.13, respectively), Entre Ríos (0.16 and 0.14, respectively) and Tucumán (0.03 and 0.04, respectively). X2X2 and X2Y5 karyomorphs were not found in wild populations but were detected at a low frequency in laboratory strains. In fact, karyomorph frequencies differed between wild populations and laboratory strains. No significant differences among A. fraterculus wild populations were evidenced in either karyotypic or chromosomal frequencies. However, a significant correlation was observed between Y5 chromosomal frequency and latitude.

CONCLUSIONS

We discuss the importance of cytogenetics to understand the possible route of invasion and dispersion of this pest in Argentina and the evolutionary forces acting under laboratory conditions, possibly driving changes in the chromosomal frequencies. Our findings provide deep and integral genetic knowledge of this species, which has become of relevance to the characterization and selection of valuable A. fraterculus sp. 1 strains for mass rearing production and SIT implementation.