The expansion of the area planted with Eucalyptus species and the trade of its products in the world have been accompanied by accidental introduction of exotic insects. The genus Phoracantha Newman (Coleoptera: Cerambycidae), from Australia and New Guinea, has 40 borer species that use trees and freshly cut logs of the genus Angophora, Corymbia, and Eucalyptus. The objective of this report is to document the occurrence of P. recurva damaging weakened C. citriodora trees in an urban area of the Atlantic rainforest in Viçosa, Minas Gerais State, Brazil. Extensive feeding galleries and the presence of a P. recurva male adult were found in the trunks of weakened trees of C. citriodora logs in an area near the forest nursery of the Universidade Federal de Viçosa. This is the first report of this borer species in this climate zone of the Atlantic rainforest biome of Minas Gerais, Brazil. This suggests that P. recurva has high plasticity to establish in regions with different climatic conditions, being able to survive in most regions of Brazil. The record of P. recurva infesting C. citriodora trees in the Minas Gerais Atlantic rainforest region increases its distribution in Brazil. This knowledge is important in reducing or preventing its damage in Brazil.
Eucalyptus species (Myrtaceae), Australian trees with fast growth and wood suitable for different purposes (Pirralho et al. 2014; IBÁ 2017), have become the trees with the largest planted area in the world. Unfortunately, the increase of the planted area with Eucalyptus spp. and related species, and the international trade of its products, are increasing accidental introductions of exotic insects (Mansfield 2016; Almeida et al. 2018).
Phoracantha Newman (Coleoptera: Cerambycidae), a genus from Australia and New Guinea with 40 longhorn borer beetle species, use healthy or weakened Angophora, Corymbia, and Eucalyptus (Myrtaceae) trees or their logs (Wang et al. 1995, 1999) for development. Trees damaged by Phoracantha spp. have decayed crowns with discolored, dried, and withered leaves, bark with cracks, and sawdust and expelled excrement (Paine et al. 2009).
Phoracantha semipunctata (Fabricius) (Coleoptera: Cerambycidae) and Phoracantha recurva Newman (Coleoptera: Cerambycidae) have been introduced accidentally into different regions of the world, where they colonize weakened trees or cut logs. These insects can survive inside the wood while it is being processed for various uses (Wang et al. 1999; Mansfield 2016). Larvae of these insects damage the trunk of host trees or their logs by forming galleries beneath their bark, with higher survival on trees that have been subjected to water stress (Hanks et al. 1991).
Phoracantha recurva, which occurs naturally in Australia and the southern part of Papua New Guinea, has high dispersal capacity and survives for long periods inside stored logs. Therefore, it has potential to infest other regions of the world. This insect has been introduced into Argentina, Chile, France, Israel, Maltese Islands, Morocco, Portugal, Spain, Tunisia, Turkey, USA, and Uruguay (Lanfranco & Dungey 2001; Mifsud 2002; Monné et al. 2002; Bybee et al. 2004; Di-Iorio 2004; Grosso-Silva 2007; Friedman et al. 2008; Faucheux 2012; Dhahri et al. 2016; Özdikmen 2017; Valladares et al. 2017). In Brazil, this borer damaged Corymbia citriodora (Hook) Hill & Johnson (Myrtaceae) logs in Paranapanema, São Paulo State, Brazil, in 2001; Eucalyptus urophylla Blake (Myrtaceae) clone logs in Lavras, a cerrado region of the state of Minas Gerais, in 2005; and it was collected in ethanolic traps in Pinheiro Machado, Rio Grande do Sul (host plants not specified) in 2011 (Wilcken et al. 2002; Santos et al. 2007; Bernardi et al. 2011).
The objective of this report is to document the occurrence of P. recurva damaging weakened C. citriodora trees in an urban area of the Atlantic rainforest in Viçosa, Minas Gerais State, Brazil. This is the first report of its occurrence in this biome of Minas Gerais State, a region with temperate climate with dry winters and hot summers (Cwa, Koppen climate classification system) (Sá Júnior et al. 2012).
Two C. citriodora trees were cut near the forest nursery of the Universidade Federal de Viçosa in early Jul 2017. Galleries were excavated under the bark (Fig. 1A), and 1 P. recurva male adult was observed in the trunk of the cut trees (Fig. 1B). The 2 C. citriodora trees had sparse crowns, leaf fall, and exit holes from adult insects on their bark. The source of the stress that predisposed these trees to P. recurva damage was not determined.
Phoracantha recurva differs from P. semipunctata by possessing long, dense gold-colored hairs below each antennal segment, and the elytra with a greater amount of cream to yellow color. The sex of P. recurva was determined by the antennae length, which is almost twice as long as the body for males, but only slightly longer for females (Wang 1995).
The importance of P. recurva is increasing worldwide due to its greater damage compared to P. semipunctata, as well as its greater reproductive capacity, faster development, and longer adult longevity (Millar et al. 2003; Bybee et al. 2004). Additionally, biological control of P. recurva populations seems to be less efficient than for P. semipunctata (Luhring et al. 2000).
Climatic conditions may favor or limit the dispersal of harmful insects to regions where their host plants are present (Liang & Fei 2014). This is the first record of P. recurva in the Atlantic rainforest of Minas Gerais State, Brazil, a temperate climate with dry winters and hot summers (Cwa) (Sá Júnior et al. 2012). This shows a high plasticity of P. recurva to establish in regions with distinct climate conditions, and suggesting that it may survive in most parts of Brazil. Suitable forest practices, such as prevention and integrated pest management programs for this and other introduced insects, are fundamental to avoid or reduce their establishment in new areas, and to reduce economic losses in regions where they are present (Paine et al. 2009).
Fig. 1.
Phoracantha recurva (Coleoptera: Cerambycidae) signs on Corymbia citriodora (Myrtaceae) trunk in Viçosa, Minas Gerais State, Brazil. Corymbia citriodora trunk bored by P. recurva larvae with oviposition sites, galleries, and adult exit holes (A), and P. recurva adult collected on the C. citriodora trunk gallery (B). Oviposition sites (I), galleries (II), adult exit holes (III), P. recurva adult (IV), and excrement (V). Photo: Norivaldo dos Anjos, 7 Jul 2017.
The record of P. recurva infesting C. citriodora logs in the Minas Gerais Atlantic rainforest region increases its distribution in Brazil; this knowledge is important to reduce or preventing its damage in Brazil.
The authors acknowledge the Brazilian agencies “Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq),” “Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)” - Finance Code 001, “Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG),” and “Programa Cooperativo sobre Proteção Florestal/PROTEF do Instituto de Pesquisas e Estudos Florestais/IPEF” for scholarships and financial support.
