Eurytoma samsonovi a new pest of apricot in Tunisia
Over the last decade in Tunisia, growers in the oasis of Gafsa have reported massive premature fruit fall in apricot (Prunus armeniaca) orchards. It was initially thought that the Mediterranean fruit fly (Ceratitis capitata) or physiological disorders were responsible for the damage. In February 2015, a large number of ‘mummified’ apricots still attached to the trees were collected and brought to the laboratory. Some of the collected fruit was dissected, and others were maintained in emergence cages. Insect larvae, pupa, and adult wasps could be found inside apricot stones, and adults also emerged from collected apricots. Laboratory studies confirmed the identity of the pest as Eurytoma samsonovi (Hymenoptera: Eurytomidae), the apricot seed wasp. Surveys were then conducted from 2017 to 2021 in the main Tunisian apricot production areas (i.e. Gafsa, Sidi Bouzid, Kairouan and Tozeur) and revealed the presence of E. samsonovi in Gafsa (Oasis Lela, Oasis El Guettar), Sidi Bouzid (Sidi Ali ben Aoun) and Tozeur (Neflayet and Deguedch). Severe damage was observed in some areas. Infested fruit either fall prematurely or became black, ‘mummified’ and remain attached to the tree. The highest infestation rates in infested orchards reached 64 to 76 %, depending on the year.
The authors recalled that E. samsonovi was first described in 1915 in the Ferghana region, in Uzbekistan, and that it has also been recorded in Armenia, India, Kyrgyzstan, Pakistan, Russia, Tajikistan, and Southern Europe*. Larvae of E. samsonovi feed on apricot nucellar tissues. The authors finally noted that considering the severity of losses observed in orchards, E. samsonovi should be considered as an emerging economic pest of apricots in Tunisia and that management measures were needed against this pest.
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* There is little data available from the literature on this insect and the EPPO Secretariat could not find recent publications to confirm the presence of E. samsonovi in Europe.
Sources
Wannassi T, Harbi A, Abbes K, Elimem M, Delvare G, Chermiti B (2022) Emergence of the apricot seed wasp Eurytoma samsonowi Vassiliev (Hymenoptera: Eurytomidae) as an economic pest of apricots in Tunisia. Phytoparasitica 50, 837-852.
Additional sources
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Narendran TC (1994) Torymidae and Eurytomidae of Indian subcontinent (Hymenoptera: Chalcidoidea). Zoological Monograph, Department of Zoology, University of Calicut, Kerala, India, pp 132-133.
Uzokov SM, Shermatov MR, Khomidova, ZM (2021) Data on the biology and harmfulness of pests (Insecta) of apricot trees in Western Fergana. TJM - Tematics Journal of Microbiology, 2277-2952. https://ssrn.com/abstract=3775399