The potential for pre-emptive biological control of Aleurocanthus woglumi (EPPO A1 List)
Why
Pre-emptive biological control can be considered for plant pests prior to a pest establishing and becoming widespread in a country at risk. Potential biological control agents (BCAs) can be identified in advance of the pest arriving and some initial screening can be conducted on their safety and suitability for the EPPO region. Aleurocanthus woglumi (Hemiptera: Aleyrodidae – EPPO A1 List) is a pest of citrus but can also be found on a wide range of crops, mostly fruit trees (Nguyen, 2008; EPPO, 2026). Native to South-East Asia, A. woglumi has been reported as a pest in other countries in Asia, North America (e.g. Florida), Central and South America, and South Africa. In the EPPO region, A. woglumi has a very restricted distribution where it is reported from Western Georgia (in Adjara, Guria and Samegrelo regions). Here, the pest is present but with a low prevalence. A. woglumi can have a high economic impact on citrus, as it produces an abundance of sugary honeydew which covers leaves and fruits making the fruit unmarketable. In some citrus producing regions fruit production can be reduced up to 80 %.
Two hymenopteran parasitoids Encarsia perplexa (Hymenoptera: Aphelinidae) and Amitus hesperidum (Hymenoptera: Platygastridae) have been proven effective classical biological control agents in several regions of the world (Milonas & Giakoumaki, 2025). Having a biological control agent ready for use in case of an outbreak of A. woglumi could help to reduce the spread of the pest. This would be particularly important for citrus producing countries in the Mediterranean Basin.
Biology and ecology
Encarsia perplexa is an arrhenotokous heteronomous parasitoid where unfertilized eggs develop into males, and fertilized eggs develop into females. Females of the species can live between four and six weeks. Development from egg to adult at a constant 24°C can take between 30 and 35 days. The parasitoid can attack any nymphal stage though it has a preference for the 2nd and 3rd instars (Milonas & Giakoumaki, 2025).
Amitus hesperidum adults live for 2 to 6 days and females can oviposit between 60-70 eggs mainly on first instar nymphs.
Feeding and efficacy
Utilised together, E. perplexa and A. hesperidum have been shown to be highly effective at controlling A. woglumi. Amitus hesperidum has been recorded to reach up to 90 % parasitism rates of A. woglumi. As part of a classical biological control programme against A. woglumi in Trinidad, A. hesperidum parasitoids were released, and citrus blackfly populations declined by more than 98% at all sites while parasitism increased to 60-90% (White et al., 2005).
Due to its longer life cycle, E. perplexa is considered as an effective biological control agent even when the population level of A. woglumi is low.
Safety
Both parasitoids have an excellent safety record where they have been released as classical biological control agents. Four years after release of E. perplexa and A. hesperidum in Dominica, there were no reports of non-target effects (Lopez et al., 2009).
History of use as a biocontrol agent
Amitus hesperidum and E. perplexa both have a long history of use as classical biological control agents against A. woglumi. They were first utilised in Mexico in 1949-1950 and subsequently used in Guam (1952), the USA (Texas (1974-1975), Florida (1976-1979), Hawaii (1998)), Dominica (1996-1997) and Trinidad. Encarsia perplexa was introduced to El Salvador in 1978.
Climatic suitability
Akrivou et al. (2021) showed that all citrus producing areas in the EPPO region are at risk from A. woglumi, under both current and future climatic scenarios. With the host able to establish, it is likely that both E. perplexa and A. hesperidum would also have a high potential for establishment in the EPPO region. Milonas & Giakoumaki (2025) citing others, note that both parasitoids adapted to the climates where they were released as classical biological control agents. Of the two biological control agents, E. perplexa is considered less susceptible to dry conditions and high temperatures than A. hesperidum.
Recommendations of the Joint EPPO/IOBC Panel on Biological Control Agents
The study of Milonas & Giakoumaki (2025) concluded that it is feasible to initiate a pre-emptive biological control programme for A. woglumi in the EPPO region. The Joint EPPO/IOBC Panel on Biological Control Agents recommends that countries at risk of A. woglumi form a consortium to initiate research into the pre-emptive biological control programme against A. woglumi using E. perplexa and A. hesperidum.
Sources
Akrivou A, Georgopoulou I, Papachristos DP, Milonas PG, Kriticos DJ (2021) Potential global distribution of Aleurocanthus woglumi considering climate change and irrigation. PLoS ONE 16(12), e0261626. https://doi.org/10.1371/journal.pone.0261626
EPPO (2026) Aleurocanthus woglumi. EPPO datasheets on pests recommended for regulation. https://gd.eppo.int (accessed 2026-09-01)
Lopez VF, Kairo MTK, Pollard GV, Pierre C, Commodore N & Dominique D (2009) Post-release survey to assess impact and potential host range expansion by Amitus hesperidum and Encarsia perplexa, two parasitoids introduced for the biological control of the citrus blackfly, Aleurocanthus woglumi in Dominica. BioControl 54(4), 497-503.
Milonas PG, Giakoumaki MV (2025) Is pre-emptive classical biological control feasible for Aleurocanthus woglumi in Europe? Biological Control 206, doi.org/10.1016/j.biocontrol.2025.105795
Nguyen R (2008) Aleurocanthus woglumi (citrus blackfly). CABI Compendium 4137, https://doi.org/10.1079/cabicompendium.4137
Thompson CR, Cornell JA & Sailerl RI (1987) Interactions of parasites and a hyperparasite in biological control of citrus blackfly, Aleurocanthus woglumi (Homoptera: Aleyrodidae), in Florida. Environmental Entomology 16(1), 140-144.