Further details on the situation of Rhagoletis completa in Italy
In the EPPO Reporting Service 97/037, the situation of Rhagoletis completa (EU Annex I/A1) in Italy was briefly presented. Since then, the EPPO Secretariat has obtained more details, especially on the damage observed. It can be recalled that R. completa was first found in Europe on walnut in 1991, in Switzerland (Ticino) and at the same time in Northern Italy (Friuli-Venezia Giulia and Veneto). In 1992, it was also observed in Lombardia and Piemonte. In 1994, it was reported in Trentino. Surveys are being carried out by using yellow sticky traps with ammonium carbonate as an attractant. They confirmed the presence of the pest in Northern Italy, and showed that R. completa was also present in a limited area in Central Italy, near Viterbo (Lazio). Damage observed is caused by oviposition punctures and the feeding of larvae on the walnut husk; as a consequence brown blotches develop on the husk and then enlarge. Usually, attacked nuts fall prematurely. In north-east Italy, damage levels up to 70-80 % have been observed. In Lombardia, a 30 % reduction in walnut production has been estimated. The authors also stressed the possibility that R. completa might attack fruit species other than walnut, and in particular peaches, although no such attacks have yet been detected in Italy. Prof. Trematerra (personal communication) indicated that very strong damage has been observed on walnut trees near apple orchards, and he has observed damage caused by Diptera (other than Ceratitis capitata) on apples, but the species was not identified.
Concerning other potential hosts of R. completa, little information can be found from the literature. Peaches are reported as occasional hosts in the Pacific Northwest of the USA (Retan, 1991). In California, Yokohama and Miller (1994) noted that in the San Joaquin valley, no larval infestations have been observed in peaches, nectarines or plums. However, in field and laboratory experiments, they have shown that peaches and nectarines can be considered as poor hosts for R. completa and plums as non-hosts. Studies on ovipositional preference of R. completa were carried on various fruits, vegetables and walnut cultivars (Abudulmadjid Kasana et al., 1995). Among fruits (other than walnut) and vegetables tested, pear was most often chosen for oviposition, followed by nectarine, apple, Capsicum, potato and tomato. But larvae completed their growth and development only in nectarine.
Abdulmadjid Kasana; Aliniazee, M.T.; Kasana, A. (1995) Ovipositional preferences of the walnut husk fly, Rhagoletis completa (Diptera: Tephritidae) on various fruits, vegetables and varieties of walnuts.
Journal of the Entomological Society of British Columbia, 82, 3-7. (CABI abstract)
Retan, A.H. (1991) Walnut husk fly.
Extension Bulletin, College of Agriculture and Home Economics, Washington State University, no. EB0904, 3pp. (CABI abstract)
Trematerra, P.; Paparatti, B.; Girgenti, P. (1995) Attenzione alla presenza della mosca delle noci.
Informatore Agrario, 51(47), 74-76.
Yokohama, V.Y.; Miller, G.T. (1994) Walnut husk fly (Diptera: Tephritidae) pest-free and preovipositional periods and adult emergence for stone fruits exported to New Zealand.
Journal of Economic Entomology, 87(3), 747-751.