Psorocampa denticulata Schaus (Lepidoptera: Notodontidae) is a pest of Eucalyptus species (Myrtales: Myrtaceae) in Brazil. The pre-pupa stage of this species is present in the soil surrounding infested trees for up to 6 mo during the dry season and can be collected and stored in large numbers. The potential use of P. denticulata pupae as an alternative host for rearing the parasitoid Palmistichus elaeisis Delvare & LaSalle (Hymenoptera: Eulophidae) was tested in the laboratory. Up to 24-h-old P. denticulata pupae (787.40 ± 78.29 mg) were individually exposed to twenty 72-h-old P. elaeisis females for 48 h. These exposed pre-pupae were individually transferred to a glass tube for the emergence either of parasitoid progeny or of the adult lepidopteran. The parasitism and emergence rates of P. elaeisis from P. denticulata pupae were 100 and 90%, respectively. The life cycle (egg to adult) was 22.22 ± 0.49 days, and the number of progeny of this parasitoid was 734.55 ± 54.56 per host. We concluded that this generalist parasitoid could be mass reared on P. denticulata pupae and released as part of an integrated program to manage lepidopteran pests in eucalyptus plantations.
The parasitoid Palmistichus elaeisis Delvare & LaSalle (Hymenoptera: Eulophidae) has potential for biological control (Pereira et al. 2010a) because it has been found parasitizing the pupae of lepidopteran defoliators of Eucalyptus species (Myrtales: Myrtaceae) in Brazil including Eupseudosoma involuta Sepp (Arctiidae), Euselasia eucerus Hewitson (Riodinidae), Sabulodes sp. (Geometridae), Dirphia moderata Bouvier (Saturniidae), Halysidota pearsoni Watson (Arctiidae), Hypsipyla grandella Zeller (Pyralidae), Thyrinteina arnobia Stoll (Geometridae), and Thyrinteina leucocerae Rindge (Geometridae) (Bittencourt & Berti Filho 1999; Pereira et al. 2008a,b, 2009; Zaché et al. 2013). In addition to these natural hosts, P. elaeisis can be reared on Tenebrio molitor L. (Coleoptera: Tenebrionidae) and Bombyx mori L. (Lepidoptera: Bombycidae) in the laboratory (Zanuncio et al. 2008; Pereira et al. 2009, 2010a).
Biological control programs with predators (Molina-Rugama et al. 1998; Torres et al. 1998) and parasitoids often rely on the availability of suitable alternative prey and hosts for economically mass rearing natural enemies (Zaviezo & Mills 2000). However, the nutritional requirements, size, age, and immune response of hosts may affect the quality of the natural enemies produced (Zanuncio et al. 1996; Silva-Torres et al. 2009; Andrade et al. 2010).
Psorocampa denticulata Schaus (Lepidoptera: Notodontidae) is a pest in Eucalyptus plantations in Brazil (Zanuncio et al. 2003). This species is a potential host for rearing parasitoids of lepidopteran defoliators of Eucalyptus species because its pre-pupae can be collected in large numbers from the soil around eucalyptus trees in areas with outbreaks of this insect (Guedes et al. 2000). Pre-pupae of P. denticulata are readily available in the soil for up to 6 mo until the onset of the rainy season, when its adults emerge. The pre-pupae of this insect can be stored, which suggests the possibility of using them as alternative host for mass rearing the parasitoid P. elaeisis during the dry period, when the populations of lepidopteran defoliators of eucalyptus are high and cause economic damage (Zanuncio et al. 1998). Therefore, the aim of this study was to evaluate the possibility of using P. denticulata as an alternative host for rearing the parasitoid P. elaeisis in the laboratory or in a mass-rearing facility.
This study was conducted in the Laboratory of Biological Control of Insects (LCBI) of the Institute of Biotechnology Applied to Agriculture (BIOAGRO) of the “Universidade Federal de Viçosa (UFV)” in Viçosa, Minas Gerais State, Brazil. The pre-pupae of P. denticulata were collected in a Eucalyptus plantation in Sete Lagoas, Minas Gerais State, Brazil, stored in cloth bags, and transported to the laboratory, where they were held in plastic trays with sterilized soil at 25 ± 1 °C, 70 ± 10% RH, and a 12:12 h L:D photoperiod until pupation.
Thirty P. denticulata pupae, in total, were placed individually in test tubes plugged with cotton wool. Next, twenty 72-h-old P. elaeisis females were placed per glass tube (14 × 2.2 cm) with one 24-h-old P. denticulata pupa (biomass of 787.40 ± 78.29 mg). The parasitoids were fed with drops of honey every 48 h (Pereira et al. 2009). After this period, the P. denticulata pupae were transferred to other glass tubes (14 × 2.2 cm) to observe the emergence of the parasitoid progeny or of the lepidopteran adults.
The percentages of parasitism and emergence, the duration of the life cycle (egg to adult), and the number of P. elaeisis progeny per P. denticulata pupa were recorded. Also, the body length (distance from the front of the head to the tip of the abdomen) and the head capsule width (distance between the eyes) of 90 males and 180 females of P. eleasis that emerged from the P. denticulata pupae were measured. The measurements were made with an ocular micrometer installed in a stereomicroscope (Pereira et al. 2010b).
Results showed that parasitism and emergence rates of the progeny of P. elaeisis were 100 and 90%, respectively, from the host pupae parasitized; the egg-to-adult period was 22.22 ± 0.49 d; and 734.55 ± 54.56 P. elaeisis individuals emerged per P. denticulata pupa. Each P. denticulata pupa produced more parasitoid progeny than those of alternative hosts such as B. mori, Diatraea saccharalis F. sensu Guenée (Lepidoptera: Crambidae), and Anticarsia gemmatalis Hübner, Heliothis virescens F., and Spodoptera frugiperda Smith & Abbot (Lepidoptera: Noctuidae) (Bittencourt & Filho Berti 1999; Pereira et al. 2010b).
Psorocampa denticulata pupae have the attributes to serve as a more suitable host to mass rear P. elaeisis than other host species such as T. arnobia and T. leucoceraeae (Pereira et al. 2008a). These attributes may include superior nutritional value (Zaviezo & Mills 2000) and larger body size (Brodeur & Boivin 2004). The duration of the P. elaeisis life cycle within P. denticulata pupae and other alternative hosts (i.e., T. molitor [Zanuncio et al. 2008]) were similar. The greater progeny of P. elaeisis per host could be related to the better nutritional quality and higher biomass of the P. denticulata pupa, such as observed for the B. mori pupa (Pereira et al. 2009). Furthermore, the larger body of P. denticulata has more resources for the immature of this parasitoid as was found in the parasitoid Apanteles galleriae Wilkinson (Hymenoptera: Braconidae) (Uçkan et al. 2004). The body length of P. elaeisis females and males that emerged from P. denticulata pupae was 1.94 ± 0.039 mm and 1.50 ± 0.022 mm, respectively, and the width of the head capsule was 0.48 ± 0.530 mm and 0.39 ± 0.011 mm, respectively. These results were similar to those of P. elaeisis reared on A. gemmatalis and B. mori pupae, which were considered suitable hosts for this parasitoid (Pereira et al. 2010b). The size of the body and the width of the head capsule of parasitoids and predators were positively correlated with reproductive traits such as fecundity, sex ratio, and the number and longevity of the offspring (Sagarra et al. 2001; Oliveira et al. 2003; Moreira et al. 2009).
This study showed that P. elaeisis can be reared on P. denticulata pupae as an alternative host to produce this parasitoid for release in biological control programs of lepidopteran pests of eucalyptus.
We thank “Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq),” “Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES),” and “Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)” for financial support. Global Edico Services edited and rewrote the English of this manuscript. We thank Jesusa C. Legaspi for revising the final version of this manuscript.