Ganaspis and Coptera show efficacy against Anastrepha fraterculus

Researchers have identified two parasitoids native to South America with high potential for biological control of fruit flies (Anastrepha fraterculus). Their study evaluated the functional responses of four species of hymenoptera associated with this pest that causes economic and phytosanitary losses in orchards in the region.

The work highlights Ganaspis pelleranoi e Coptera haywardi as viable candidates for augmentative biological control programs. These species exhibited high attack rates and good host utilization, in addition to characteristics that favor their adaptation to production systems and field releases.

The phytosanitary problem

Anastrepha fraterculus is one of the main fruit pests in South America. The presence of this fly in fruit-producing regions creates quarantine barriers, hindering exports. In Brazil and Argentina, this species coexists with the also invasive Ceratitis capitata, requiring specific management strategies.

Until now, biological control with native parasitoids had not been applied on a large scale against A. fraterculus. The use of the sterile insect technique (SIT), although already used against C. capitata, is not yet available for A. fraterculus. Options are limited to traps, chemical control, and cultural practices.

Parasitoids evaluated

The research investigated the performance of four species of native parasitoids:

• Coptera haywardi (Diapriidae) – pupal parasitoid

• Ganaspis pelleranoi (Figitidae) – larval parasitoid

• Doryctobracon crawfordi (Braconidae) – larval parasitoid

• Opius bellus (Braconidae) – larval parasitoid

The experiments were conducted at the PROIMI-CONICET laboratory in Argentina, with individuals artificially raised for up to 48 generations. The researchers exposed different densities of larvae and pupae to A. fraterculus to the female parasitoids and analyzed the attack patterns with the statistical package “frair”, from the R software.

Functional responses

Functional response describes how a parasitoid responds to different host densities. It allows predicting the attack rate and effectiveness of the natural enemy, making it a useful tool for selecting biological control agents.

The study showed that:

• G. pelleranoi presented a type III functional response, which indicates an increase in attack rate as host density increases. This response suggests greater ecological stability.

• C. haywardi, D. crawfordi e O. bellus presented type II responses, where the attack rate stabilizes or decreases with increasing host density.

• G. pelleranoi had the shortest host manipulation time, which increases its efficiency.

• C. haywardi e G. pelleranoi were the most effective in terms of attack rate and low number of discarded hosts.

Biological control

The data indicate that G. pelleranoi stands out as a highly efficient larval parasitoid, especially at high host densities. Already C. haywardi It acts more efficiently at low pupal densities, offering a complementary action in the control system.

Both species also demonstrated a lower proportion of discarded hosts, which reduces losses in rearing systems and mass releases. Analyzing these rates is essential for adjusting parasitoid-host ratios in rearing and release programs.

Field use

The study is part of a line of research initiated in 2010 in Argentina, focused on the colonization and use of native parasitoids against fruit pests. The next step involves transitioning from experimental management to large-scale production and subsequent field application.

According to the authors, the adoption of native parasitoids in augmentative biological control programs represents an ecologically sustainable alternative. Furthermore, the results contribute to the selection of more efficient species adapted to local environmental conditions, reducing dependence on exotic species such as Diachasmimorpha longicaudata.

Further information at doi.org/10.3390/insects16090919