# The Parasitoid Complex of Aleurothrixus floccosus (Hemiptera: Aleyrodidae) in the Citrus Groves of Central–Southern Italy

## TL;DR

Researchers found new parasitoid species in Italy that help control the invasive woolly whitefly, a pest in citrus groves.

## Contribution

The study reports the first records of Eretmocerus paulistus and Signiphora xanthographa in Italy and Europe, expanding the biological control potential for Aleurothrixus floccosus.

## Key findings

- Eretmocerus paulistus and Signiphora xanthographa were newly documented in Italy and Europe.
- These parasitoids showed high parasitism rates of woolly whitefly nymphs.
- The parasitoid complex includes both primary and hyperparasitoid species, influencing pest control effectiveness.

## Abstract

The woolly whitefly Aleurothrixus floccosus, an invasive species in Italy, was first reported in 1974. Due to the limited efficacy of insecticides, its management relies primarily on classical biological control, notably through introducing the biological control agents Cales noacki and Amitus spiniferus. Approximately thirty years later, between 2024 and 2025, new surveys conducted in organic citrus orchards revealed a diversification of the parasitoid community associated with A. floccosus. These investigations confirmed the activity of two additional Neotropical species: Eretmocerus paulistus and Signiphora xanthographa. These findings represent new records for Italy and Europe, respectively. Their parasitic activity, distribution in various central and southern Italy locations, and ecological interactions with the host and among parasitoids are described.

The woolly whitefly, Aleurothrixus floccosus, is likely a Neotropical origin species that has spread globally. Introduced to France in 1969, it became a pest in southern European citrus groves, first reported in Italy in 1974. Integrated management using biological control agents is crucial due to the low efficacy of chemical controls. Nymphs produce waxy filaments and honeydew, limiting insecticide contact. Natural enemies, especially from Neotropics, have been documented. The parasitoids Amitus spiniferus and Cales noacki were released in France in 1970 and later observed in Liguria, Italy. In the Campania region, C. noacki was first found on Aleurotuba jelineki in 1984 and this finding preceded the first report of A. floccosus in the same area. Subsequently, C. noacki was also introduced in other regions where it showed better adaptation throughout the Italian territory, reaching high parasitization levels on the woolly whitefly nymphs. After many years since the last field investigations, surveys in 2024–2025 in organic citrus groves in central and southern Italy identified additional parasitoids. Besides C. noacki and A. spiniferus, Eretmocerus paulistus and Signiphora xanthographa were found for the first time in Italy. Both species were originally described from the Neotropical ecozone. The aphelinid finding represents its first documented establishment in Italy, while the signiphorid one represents a new record for the European fauna. E. paulistus is a primary parasitoid, while S. xanthographa is a hyperparasitoid that can limit the effectiveness of other parasitoids. The interaction of these parasitoids resulted in high parasitism rates for A. floccosus nymphs. Preserving the current complexity of parasitoids in integrated pest management (IPM) programs could effectively control the woolly whitefly in central and southern Italy.