Taxonomy, biology, and efficacy of two Australian parasitoids of the eucalyptus gall wasp, Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae: Tetrastichinae)

Abstract

Two species of Tetrastichinae (Hymenoptera: Eulophidae) from Australia are described as parasitoids of Leptocybe invasa Fisher & La Salle: Quadrastichus mendeli Kim & La Salle sp.nov. and Selitrichodes kryceri Kim & La Salle sp. nov. These parasitoids were introduced to Israel as part of a biological control program to counter the severe levels of damage caused by L. invasa to Eucalyptus plantations throughout the Mediterranean Basin. The biology of these species, as well as their potential as biological control agents, is discussed. Both species are now successfully established in Israel. The parasitoids were collected from L. invasa galls on 3–4 year old Eucalyptus tereticornis trees in central west Queensland, between Gympie and Hervey Bay, and on the Atherton Tableland. Both species are small (about 1 mm in length), solitary, and apparently ectoparasitic wasps. S. kryceri is biparental whereas Q. mendeli is uniparental. Maximum survival (~ 6 days at 25°C) for both species was obtained when they were fed with honey solution. S. kryceri and Q. mendeli successfully parasitized approximately 2.2 and 2.5 gall units per day, respectively. Both species developed on both young and mature host larvae. L. invasa may be considered as an early colonizer of regenerated young stands in Australia, which may imply that its parasitoids will display a similar fast-tracking behavior with respect to their host in its invasive range. The generic status of Selitrichodes is reinstated, with Epomphaloides and Zagrammosomoides placed as new synonyms of Selitrichodes.

First record ofQuadrastichus mendeli, a parasitoid ofLeptocybe invasa, in South Africa

“…This study provides the first report of Q. mendeli in South Africa and in sub-Saharan Africa. Quadrastichus mendeli is a parasitoid of young and mature L. invasa larvae and it is currently unknown whether the larvae are killed immediately or shortly after parasitization (Kim et al 2008). Quadrastichus mendeli is a uniparental and solitary parasitoid with an approximate developmental time of 30 days at 28.1°C (Kim et al 2008).…”

“…Quadrastichus mendeli is a parasitoid of young and mature L. invasa larvae and it is currently unknown whether the larvae are killed immediately or shortly after parasitization (Kim et al 2008). Quadrastichus mendeli is a uniparental and solitary parasitoid with an approximate developmental time of 30 days at 28.1°C (Kim et al 2008). Laboratory studies in Israel have shown a parasitism rate of between 7.9 and 84%, depending on the life stage attacked (Kim et al 2008).…”

“…In addition to this deliberate movement of Q. mendeli it has also been reported in Italy as an unintentional introduction (Nugnes et al 2016). Morphological characteristics described by Kim et al (2008) were used to tentatively identify the hymenopteran. Specific characteristics included a small body size (1.15-1.35mm), a mainly yellow body with dark brown markings, antennae with three funicular segments longer than they are wide and a large anellus, as well as a gaster longer than the head plus mesosoma.…”

Diversity in Eucalyptus susceptibility to the gall‐forming wasp Leptocybe invasa

“…However, biological control is a preferred strategy that has shown much promise. For example, the parasitic wasps, Quadrastichus mendeli Kim & La Salle (Hymenoptera: Eulophidae) and Selitrichodes kryceri Kim & La Salle (Hymenoptera: Eulophidae) have been introduced to Israel from Australia in an effort to control L. invasa in the Mediterranean region (Kim et al , 2008). An Australian Megastigmus species (Hymenoptera: Torymidae) (Doğanlar & Hassan, 2010), two Megastigmus species native to Israel and Turkey (Protasov et al , 2008) and a range of parasitoids native to India (Kulkarni et al , 2010), have also been used.…”

“…An Australian Megastigmus species (Hymenoptera: Torymidae) (Doğanlar & Hassan, 2010), two Megastigmus species native to Israel and Turkey (Protasov et al , 2008) and a range of parasitoids native to India (Kulkarni et al , 2010), have also been used. Detailed work on the biology of S. kryceri and Q. mendeli has shown parasitism levels of 52% and 73%, respectively (Kim et al , 2008).…”