Parasitoid guild of the citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) in Tunisian citrus orchards and a new report of Cirrospilus ingenuus Gahan (Hymenoptera: Eulophidae)

Abstract

A survey of the parasitoid species of the citrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), a cosmopolitan  pest of citrus, was carried out in 2019 and 2020 in the major citrus production area of Tunisia. Four different Eulophidae species were  found: Citrostichus phyllocnistoides (Narayanan), representing 81.82% of the identified parasitoids, Semielacher petiolatus (Girault)  (9.40%) and the native species Pnigalio pectinicornis (L.) (2.82%). Cirrospilus ingenuus Gahan (Hymenoptera: Eulophidae) is a new report  for the parasitoid entomofauna of P. citrella in the country, representing 5.96% of the identified parasitoids. It has probably spread  naturally from other Mediterranean regions. Predation by generalist predators is the main mortality factor of CLM (up to 59.11% of the  mortality was caused by natural enemies), followed by parasitism (oviposition) (22.47%) and host-feeding (18.42%). Second and third  instar larvae of the CLM were the preferred stages for parasitism. Host-feeding and generalist predators’ attacks were most common on  first and second instars. Data highlighting the ability for C. phyllocnistoides to develop and disperse clearly predominates in Tunisian  citrus orchards. Citrostichus phyllocnistoides may compete with S. petiolatus, exerting a complementary action to that of C.  phyllocnistoides, particularly earlier in the season when the densities of the latter species are low. Further studies focusing on inter- specific relationships between these two exotic parasitoids are needed in order to test whether the observed field results could have  been estimated from laboratory assays. This will be helpful in critically evaluating the results of the classical biological control programme  developed against CLM in Tunisia.