Trichomma enecator (Rossi, 1790)

Scaramozzino, Pier Luigi, Giovanni, Filippo Di, Loni, Augusto, Ricciardi, Renato & Lucchi, Andrea, 2018, Updated list of the insect parasitoids (Insecta, Hymenoptera) associated with Lobesiabotrana (Denis & Schiffermueller, 1775) (Lepidoptera, Tortricidae) in Italy. 2. Hymenoptera, Ichneumonidae, Anomaloninae and Campopleginae, ZooKeys 772, pp. 47-95 : 47

Trichomma enecator (Rossi, 1790) Figure 2

Trichomma enecator : Colombera et al. 2001: 94; Scaramozzino et al. 2017b: 133.

Italian distribution of reared parasitoids.

Piedmont: Colombera et al. 2001.

Tuscany: Scaramozzino et al. 2017b.

Distribution.

Palaearctic species occurring throughout Europe, Canary Islands, Near East (Turkey and Syria), Northern and Central Russia, Kazakhstan, Russian Far East, Korea and Japan ( Yu et al. 2012; Zwakhals and van Achterberg 2017). In 1931, it was released in North America (New Jersey, USA) to control the Oriental fruit moth, without becoming established ( Carlson 1979).

Host range.

Females lay eggs on young larvae that live hidden in the vegetation. Yu et al. (2012) list 28 host species, many of which belong to the family Tortricidae , including the fruit crop pests Cydia pomonella (Linnaeus, 1758), Archips rosana (Linnaeus, 1758) and Grapholita molesta (Busck, 1916). The following species need to be added to the list: Aphelia (Zelotherses) peramplana ( Hübner, 1825) (= A. amplana Hübner, 1813) ( Vas et al. 2015), Archips crataegana ( Hübner, 1799) ( Lungu-Constantineanu 2009), Cacoecimorpha pronubana ( Hübner, 1799) ( Scaramozzino et al. 2017b), Cydia pactolana (Zeller, 1840) ( Jansons 2013), Eudemis profundana (Denis & Schiffermüller, 1775) ( Zaemdzhikova 2017), Sparganothis pilleriana (Denis & Schiffermüller, 1775) ( Habermehl 1922), Spilonota ocellana (Denis & Schiffermüller, 1775) ( Nuzhna 2010) among the Tortricidae ; Anacampsis populella (Clerck, 1759) ( Hassanein 1978) among Gelechiidae ; Macrothylacia rubi (Linnaeus, 1758) ( Nuzhna 2010) among Lasiocampidae ; Acrobasis suavella (Zincken, 1818) ( Morley 1915) among Pyralidae ; and Prismosticta fenestrata Butler, 1880 among Endromidae ( Morley 1915). Habermehl (1922) reports as host also Gelechia boticella , but the identity of this species still remains unclear.

Ultimately, 40 host species of Trichomma enecator have been reported: 25 species belonging to Tortricidae , three each to Gelechiidae and Pyralidae , and one each to Elachistidae , Endromidae , Erebidae ( Lymantria dispar (Linnaeus, 1758)), Gracillariidae , Lasiocampidae , Noctuidae , Nolidae and Psychidae . The record by Starke (1956 in Yu et al. 2012) of Plioreocepta poeciloptera (Schrank, 1776) ( Diptera Tephritidae ) seems unlikely and is probably wrong.

In Italy, T. enecator is reported on: Earias clorana (Linnaeus, 1761) ( Lepidoptera Nolidae ) on goat willow ( Salix caprea Linnaeus, 1753) ( Leonardi 1925); Cydia pomonella in Campania ( Sciarra 1915) and Emilia Romagna ( Faggioli 1938); Tortrix viridana Linnaeus, 1758 and Aleimma loeflingiana (Linnaeus, 1758) ( Lepidoptera Tortricidae ) on oak in Calabria and Campania, respectively ( Silvestri 1923); Grapholita molesta in Emilia Romagna ( Grandi 1937); Rhyacionia buoliana (Denis & Schiffermüller, 1775) in Tuscany ( Zocchi 1952); Cacoecimorpha pronubana feeding on spurge flax ( Daphne gnidium Linnaeus, 1753) in Tuscany ( Scaramozzino et al. 2017b).

Ecological role.

Trichomma enecator is a solitary, koinobiont, larval-pupal endoparasitoid on fruit-mining or other concealed lepidopterous larvae. It is one of the most common parasitoids of the codling moth in Europe ( Franck et al. 2017). Although quite common, its control action on the codling moth is limited, with parasitization rates rarely exceeding 5% (Table 4), being inexplicably absent in some apple orchards ( Maalouly et al. 2013).

What we know about its biology is mainly due to Rosenberg (1934), who studied the codling moth in French apple orchards. This parasitoid attacks the host larvae, hibernating in the larval stage inside the host; the adult emerges from the pupa, some weeks before the host; the emergence period, in outdoor insectary, lasts 10-24 days, from the second half of May to the beginning of June. In captivity both genders may live approximately a month. Females start to oviposit one or two days after emergence, and their eggs hatch in approximately eight days ( Rosenberg 1934). Despite its presence in most of the areas in Rosenberg’s survey, the parasitism rate never surpassed 3.11%.

Trichomma enecator females parasitize all the larval instars of the codling moth inside the fruits. The females are attracted by exudates that accumulate on the surface of the fruits infested by the codling moth larvae; in the absence of these exudates, the parasitization behavior is disrupted ( Mills and Dixon 1993). To breed this species in insectarium is very difficult ( Mills 2005), even if Russ and Faber (1978) were able to rear it until F6 generation by the same method used to rear Ascogaster quadridentatus Wesmael, 1845 ( Hymenoptera , Braconidae ).

At our latitude, T. enecator is a multivoltine species, while in Central-Northern Europe ( Gauld and Mitchell 1977, Sedivy 2001) and Spain ( Miñarro and Dapena 2004) it is presumably bivoltine. According to our personal observations, in Italy it shows three generations per year, and can attack all three generations of EGVM.

Trichomma enecator has a secondary importance on EGVM; Telenga (1934) obtained it in early June in Crimea. In Piedmont (Italy), a single specimen emerged from pupae of the overwintering generation of L. botrana ( Colombera et al. 2001). In the Natural Reserve of San Rossore (Pisa, Tuscany), we obtained 13 specimens of T. enecator from EGVM pupae in July 2012 and from EGVM and C. pronubana pupae in May and July 2014. Pupae of both tortricids were collected into the nests formed by the larva on the apical buds of the spurge flax Daphne gnidium ( Malvales , Thymelaeaceae ) ( Scaramozzino et al. 2017b).