Eucalyptus cloeziana F. Muell. (Myrtales: Myrtaceae) and the tropical almond Terminalia catappa L. (Myrtales: Combretaceae) are widely cultivated in urban and forest areas of many countries where biological control is the most-preferred method to control insects. Aximopsis sp. (Hymenoptera: Eurytomidae) is reported for the first time in Brazil in a new group of lepidopteran hosts. Individuals of this species emerged from the pupae of Thyrinteina arnobia arnobia Stoll (Lepidoptera: Geometridae) and Thagona tibialis Walker (Lepidoptera: Lymantriidae) that developed from larvae defoliating E. cloeziana and T. catappa plants on the campus of the Universidade Federal de Viçosa (UFV) in Viçosa, Minas Gerais, Brazil. Aximopsis sp. was identified by comparing it with species of this group as described for the Neotropical region. Voucher specimens were deposited in the Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), France. Twenty new pupae each of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae) and Tenebrio molitor L. (Coleoptera: Tenebrionidae) were held individually in test tubes with a drop of honey as food and 3 mated Aximopsis sp. females for 2 d. Aximopsis sp. parasitized 20% of the T. molitor pupae but none of the A. gemmatalis pupae. The duration of the life cycle (egg to adult), parasitism and emergence rates, total individuals emerged from each pupa, sex ratio, length of the body and width of the head capsule, and the longevities of Aximopsis sp. males and females that emerged from parasitized T. molitor pupae were evaluated. The duration of the life cycle of Aximopsis sp. was 14 ± 2 d. An average of 62 ± 5 Aximopsis sp. individuals emerged from each T. molitor pupa, and their sex ratio was 0.96 ± 0.02. The total number of parasitoids that emerged was 248 individuals. Measurements of characters of progeny Aximopsis sp. females (n = 10) and males (n = 5), respectively, were as follows: body length: 3.50 mm (2.40-3.80 mm) and 1.99 mm (1.97-2.02 mm); head capsule width: 0.63 mm (0.58-0.72 mm) and 0.48 mm (0.46-0.51 mm), and longevity: 6 ± 1 d and 4 ± 1 d. These results open prospects for investigations of biological control of pests with this natural enemy.
Eucalyptus cloeziana F. Muell. (Myrtales: Myrtaceae) is cultivated in urban and forest areas to supply raw material for blacksmithing, props, structures, sleepers, and, especially, poles (Dall'Oglio et al. 2013). However, this plant does not thrive in regions with frost, soils with low fertility, altitudes above 1,600 m, fires, and severe water deficits, and it has reduced sprouting (Marques et al. 1996; Okino et al. 2004). Eucalyptus cloeziana can be infested by Ctenarytaina spatulata Taylor (Hemiptera: Aphalaridae), although other species of eucalyptus and other Myrtaceae are preferred by this aphalarid for feeding and oviposition (Queiroz et al. 2010). Furthermore, E. cloeziana is susceptible to defoliation by Hylesia paulex Dognin (Pereira et al. 2009) and Dirphia moderata Bouvier (Lepidoptera: Saturniidae) (Zanuncio et al. 1998; Pereira et al. 2008a) and suffers extensive damage from Thyrinteina arnobia arnobia Stoll and Thyrinteina leucoceraea Rindge (Lepidoptera: Geometridae) (Lemos et al. 1999; Pereira et al. 2008b).
Lepidopteran defoliators of Eucalyptus species can be controlled with chemical insecticides (Elek et al. 2003; Mansfield et al. 2006), but biological control with pupal parasitoids can reduce applications of these expensive and sometimes problematic products (Tavares et al. 2014a). The identification of natural enemies is the first step to develop biological control techniques in integrated management of a forest pest (Dall'Oglio et al. 2013). Thus, it is significant that Palmistichus elaeisis Delvare & LaSalle and Trichospilus diatraeae Cherian & Margabandhu (Hymenoptera: Eulophidae) were found to parasitize T. arnobia arnobia pupae on E. cloeziana plants (Pereira et al. 2008b,c), and the development and reproduction of P. elaeisis in T. arnobia arnobia pupae were studied in the laboratory (Pereira et al. 2010).
The number of natural enemies associated with T. arnobia arnobia may be great than currently is known, because Paropsis atomaria Olivier (Coleoptera: Chrysomelidae), the main pest of E. cloeziana in Australia, has a large number of egg and larval parasitoids and hyperparasitoids (Nahrung et al. 2008). The main natural enemy of this pest is Neopolycystus sp. (Hymenoptera: Pteromalidae), which was found to parasitize 45% of this beetle's eggs (Duffy et al. 2008). The aim of this study was to identify parasitoids of T. arnobia arnobia pupae on E. cloeziana plants in an urban area of Brazil and determine their parasitism rate on alternative hosts in order to develop mass production methods for use in biological control programs.
Materials and Methods
Thyrinteina arnobia arnobia pupae of various ages were collected on E. cloeziana plants at the campus of the Universidade Federal de Viçosa (UFV) in Viçosa, Minas Gerais, Brazil (20°44′S, 42°50′W; 650 m asl) in 2007. In 2011, Thagona tibialis Walker (Lepidoptera: Lymantriidae) pupae of various ages were obtained from larvae defoliating Terminalia catappa L. (Myrtales: Combretaceae) trees, which are cultivated in urban areas and on the campus of UFV (20°45′S, 42°51′W, 651 m asl). These pupae were brought to the Laboratory of Biological Control of Insects (LCBI) of UFV and kept in a room at 25 ± 1 °C, a 12:12 h L:D photoperiod, and 70 ± 10% RH. Each pupa was placed in a test tube (14.0 cm long × 2.2 cm diameter), which was sealed with a cotton swab until emergence of the lepidopteran or parasitoids. The collection areas were subjected to human impact and presented a flat terrain near a fragment of secondary forest with a diversified flora and fauna (Pereira et al. 2009; Tavares et al. 2011b, 2012c).
IDENTIFICATION OF INSECTS
Seventy-three individuals of an undescribed gregarious endoparasitoid species belonging to the genus Aximopsis (Hymenoptera: Eurytomidae), emerged from 1 T. arnobia arnobia pupa collected in Nov 2007 on E. cloeziana plants. In addition, 73 and 79 Aximopsis individuals emerged from 2 T. tibialis pupae sampled on a T. catappa tree in May and Jun 2011, respectively. This parasitoid was identified by Gerard Delvare of the Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), France, from initial comparison with the types of Neotropical Eurytomidae housed in the U.S. National Museum of Natural History, Washington D.C., USA, and the Natural History Museum, London, United Kingdom. Individuals of this species were deposited in the CIRAD and in the Regional Museum of Entomology of the Department of Entomology at UFV.
Twenty recent Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae) (271.7 ± 6.8 mg) and Tenebrio molitor L. (Coleoptera: Tenebrionidae) (118.0 ± 5.6 mg) pupae were obtained from cultures of these species reared at UFV (Zanuncio et al. 2008; Pereira et al. 2010). Larvae of A. gemmatalis had been fed with a solid artificial diet composed of 125.0 g bean grains, 62.4 g yeast, 100.0 g wheat germs, 100.0 g soy protein, 50.0 g casein, 35.0 g agar, 5.0 g Nipagin®, 6.0 g ascorbic acid, 3.0 g sorbic acid, 6.0 mL formaldehyde at 40.0%, and 10.0 mL vitamin solution (Pereira et al. 2010). Larvae of T. molitor had been fed ad libitum with wheat bran (12% protein, 2% lipids, 75% carbohydrates, and 11% minerals/sugar) and pieces of Saccharum officinarum L. (Poales: Poaceae) and Sechium edule (Jacq.) Swartz (Cucurbitales: Cucurbitaceae). Sheets of paper were placed on top of the substrate to reduce the intensity of the light on the insects (Zanuncio et al. 2008).
Each pupa was individualized in a test tube with a drop of honey and 3 mated Aximopsis sp. females that had emerged from T. tibialis pupae. These insects remained in the test tubes for 2 d according to the method proposed for parasitism of A. gemmatalis and T. molitor pupae by P. elaeisis in the laboratory (Zanuncio et al. 2008; Pereira et al. 2010). Parasitism and emergence rates of parasitoids emerged from A. gemmatalis and T. molitor pupae were evaluated according to the number of parasitized pupae presenting caramel color. Unviable pupae became black, hollow, and died, whereas adult lepidopterans or coleopterans emerged from the non-parasitized ones (Zanuncio et al. 2008; Pereira et al. 2010).
The design was completely randomized with 2 treatments represented by A. gemmatalis and T. molitor pupae. Each treatment had 20 replications (1 pupa each). The duration of the life cycle (egg to adult, in d), parasitism and emergence rates (%), number of emerged individuals from each pupa, sex ratio, length of the body and width of the head capsule, and the longevity of Aximopsis sp. females and males that emerged from host pupae were determined according to the method proposed for parasitism of Heraclides anchisiades capys Hübner (Lepidoptera: Papilionidae) pupae by P. elaeisis in the laboratory (Tavares et al. 2013c).
Aximopsis sp. did not parasitize A. gemmatalis pupae, but it parasitized T. molitor pupae, which resulted in parasitism and emergence rates of 20% and 62 ± 5 individuals per pupa of this latter host (Table 1). The duration of the life cycle (egg to adult) of Aximopsis sp. was 14 ± 2 d. The sex ratio was 0.96 ± 0.02. The total number of parasitoids that emerged was 248 individuals. The longevity of Aximopsis sp. females was 6 ± 1 d and that of males was 4 ± 1 d. The body length and the width of the head capsule of Aximopsis sp. progeny were 3.50 mm (2.40-3.80 mm) and 0.63 mm (0.58-0.72 mm), respectively, in females (n = 10) and 1.99 mm (1.97-2.02 mm) and 0.48 mm (0.46-0.51 mm), respectively, in males (n = 5).
This is the first report of an Aximopsis sp. parasitizing lepidopteran pupae, i.e., T. arnobia arnobia and T. tibialis. Individuals of Aximopsis sp. that emerged from pupae of these 2 hosts in Brazil differed in their morphology from other species of this genus. Prior to this report, Aximopsis was known to parasitize only hymenopteran hosts. Thus, Aximopsis sp. that emerged from T. arnobia arnobia and T. tibialis pupae appear to be representatives of a new group that specializes on lepidopteran host species.
The identification of Aximopsis sp. parasitizing T. arnobia arnobia pupae is important, because the pupal stage has no defense, whereas the larvae can reduce the impact of natural enemies by camouflage, by attacking natural enemies with their jaws, and by hanging from silk threads (Soares et al. 2009).
The number of individuals of Aximopsis sp. that emerged per T. molitor pupa (62 ± 5) was smaller than the numbers of P. elaeisis obtained in the following cases: (i) 4 P. elaeisis females per T. molitor pupae resulted in 100% parasitism, 90.8% emergence, and 70 ± 3 individuals per pupa (Zanuncio et al. 2008), (ii) 6 P. elaeisis females per A. gemmatalis pupa resulted in 100% parasitism,100% emergence, and 110 ± 19 individuals per pupa (Pereira et al. 2010), (iii) 10 P. elaeisis females per H. anchisiades capys pupa resulted in 40% parasitism, 40% emergence, and 323 ± 38 individuals per pupa (Tavares et al. 2013c), and (iv) 10 Trichospilus pupivorus Ferrière (Hymenoptera: Eulophidae) females per A. gemmatalis pupa resulted in 35% parasitism, 35% emergence, and 242 ± 12 individuals per pupa (Tavares et al. 2011a).
Parameters (mean ± SD, or range) of Aximopsis sp. that parasitized pupae of Tenebrio molitor in the laboratory.
This lower number of individuals of Aximopsis sp. that emerged per T. molitor pupa compared with other cases may be because of the greater body length and the greater width of the head capsule of Aximopsis sp. female and male progeny than those of P. elaeisis (2.00 ± 0.03 mm and 0.58 ± 0.01 mm, respectively, in females and 1.34 ± 0.02 mm and 0.45 ± 0.01 mm, respectively, in males) that emerged from T. molitor pupae (Zanuncio et al. 2008) and the width of the head capsule of female and male T. diatraeae (0.71 ± 0.01 mm and 0.55 ± 0.02 mm, respectively) that emerged from T. arnobia arnobia pupae (Pastori et al. 2012).
This first report of Aximopsis sp. parasitizing pupae of T. arnobia arnobia and T. tibialis in Brazil opens possibilities for biological control of these pests in Eucalyptus plantations and on T. catappa plants in urban and forest areas by producing and releasing this natural enemy. The initial infestation of T. tibialis (population peak in May) on T. catappa plants (Tavares et al. 2013b, 2014b) near E. cloeziana plantations may have contributed to the dispersion, parasitism, and occurrence of Aximopsis sp. in Nov in T. arnobia arnobia pupae. Terminalia catappa is cultivated along the Atlantic coast of Brazil and in municipalities of Amapá, Pará, and Roraima States, which border French Guiana, Guyana, and Suriname (Tavares et al. 2011a, 2012a). This area may be the region of entrance and distribution of Aximopsis sp. to central Brazil. Terminalia catappa plants are grown near Eucalyptus crops, and those plants can be a refuge for natural enemies of forest pests, just as has been reported for agricultural crops where Crotalaria juncea L. (Fabales: Fabaceae) shelters natural enemies of pests of Zea mays L. (Poales: Poaceae) (Tavares et al. 2011c). Thagona tibialis pupae are also hosts of the eulophid parasitoids P. elaeisis and T. pupivorus, which are promising biological control agents of agricultural pests such as A. gemmatalis, a major defoliator of Glycine max (L.) Merr. (Fabales: Fabaceae) (Tavares et al. 2011a, 2012a,b, 2013a).
This newly discovered Brazilian species of Aximopsis is most similar to one that parasitizes Sibine sp. (Lepidoptera: Limacodidae) pupae in the Neotropical region, and which is deposited in the collection of CIRAD (G. Delvare, pers. com.). Probably, the Brazilian species is native to South America, although the Australasia fauna of this genus is largely unknown. The phylogenetic position of the genus Aximopsis Ashmead in the Eurytominae has been redefined (Gates et al. 2006). Additional phylogenetic studies of the species of this genus are needed, because it is extremely diverse in the Neotropical region. The DNA of some Eurytominae species was sequenced in order to verify a phylogenetic analysis based on morphological characters (Lotfalizadeh et al. 2007).
The Aximopsis sp. that emerged from T. arnobia arnobia and T. tibialis pupae appears to be representative of a new group of Aximopsis that specializes on host species differing from those parasitized by Aximopsis masneri Gates (Hymenoptera: Eurytomidae). The latter species parasitizes Euglossa variabilis Friese and Euglossa cybelia Moure (Hymenoptera: Apidae) in nests of these wasps in the Neotropical region (Gates 2009).
This is the first report of a species of the genus Aximopsis in Brazil. In addition, Aximopsis sp. parasitized Lepidoptera pupae of forest pests of the families Geometridae and Lymantriidae, which constitute a host group not previously known to be parasitized by species of Aximopsis. Tenebrio molitor, an adequate alternative host for some forest parasitoids in Brazil, has the potential to be used for mass rearing Aximopsis sp. in the laboratory. This study opens prospects for programs of biological control of pests with this natural enemy in urban and forest plantation areas of E. cloeziana and T. catappa.
We extend heartfelt thanks to Olaf Hermann Hendrik Mielke (Universidade Federal do Paraná, Departamento de Zoologia in Curitiba, Paraná, Brazil) for confirming the scientific name of Thyrinteina arnobia arnobia Stoll (Lepidoptera: Geometridae). We acknowledge 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 of India rewrote and edited the English of the submitted version of this manuscript.