Feeding and oviposition preferences of Ctenarytaina spatulata Taylor (Hemiptera, Psyllidae) for Eucalyptus spp. and other Myrtaceae in Brazil

Preferência de alimentação e oviposição de Ctenarytaina spatulata Taylor (Hemiptera, Psyllidae) por Eucalyptus spp. e outras Myrtaceae

SHORT COMMUNICATION

Feeding and oviposition preferences of Ctenarytaina spatulata Taylor (Hemiptera, Psyllidae) for Eucalyptus spp. and other Myrtaceae in Brazil

Preferência de alimentação e oviposição de Ctenarytaina spatulata Taylor (Hemiptera, Psyllidae) por Eucalyptus spp. e outras Myrtaceae

Dalva Luiz de Queiroz^I; Keti M. R. Zanol^II; Edílson B. Oliveira^I; Norivaldo dos Anjos^III; Jonathan Majer^IV

^IEmbrapa Florestas, Estrada da Ribeira, Km 111, Caixa Postal 319, 83411-000 Colombo-PR, Brazil. [e-mail]

^IIDepartmento de Zoologia, Universidade Federal de Paraná, Caixa Postal 19020, 81513-990 Curitiba-PR, Brazil. [e-mail]

^IIIDepartmento de Biologia Animal, Universidade Federal de Viçosa, 36570-000 Viçosa-MG, Brazil. [e-mail]

^IVDepartment of Environmental Biology, Curtin University of Technology, P. O. Box U 1987, Perth-WA 6845, Australia. [e-mail]

ABSTRACT

Feeding and oviposition preferences of Ctenarytaina spatulata Taylor (Hemiptera, Psyllidae) for Eucalyptus spp. and other Myrtaceae in Brazil. The Australian psyllid, Ctenarytaina spatulata Taylor (Hemiptera, Psyllidae), was first detected in Brazil in 1994, where it was found on drought-affected shoots of Eucalyptus grandis in a plantation located in the northern part of Paraná State. The oviposition and feeding preferences of this psyllid were examined on 19 Eucalyptus species, one Eucalyptus hybrid (Cambiju), three Corymbia species and four native Myrtaceae species (Hexaclames edulis, Marlieria edulis, Plinia trunciflora, and Psydium sp.) under greenhouse conditions. The largest populations of C. spatulata were found on E. robusta and E. pellita, while sizeable infestations were also found on E. urophylla, E. grandis, and the Cambiju hybrid. The plants with the greatest symptoms of damage were E. grandis and E. resinifera. Eucalyptus cinerea, E. benthamii, E. pilularis, and E. dunnii were not infested and E. cloeziana was minimally infested. Among the Corymbia species, the number of eggs of C. spatulata was very low on C. citriodora and C. torelliana. No eggs and nymphs of C. spatulata were found on native Brazilian Myrtaceae. The number of eggs on plants was highly correlated with the subsequent levels of nymphs, suggesting that egg counts can be used as a viable monitoring tool to assist with the integrated management of this pest.

Keywords: Exotic pest; forest pest; psyllid.

RESUMO

Ctenarytaina spatulata Taylor, 1997 (Hemiptera, Psyllidae), originária da Austrália, foi detectada no Brasil em 1994. Sua ocorrência foi inicialmente observada em E. grandis no Norte do Paraná associada à seca dos ponteiros. Com o objetivo de verificar a preferência deste psilídeo para postura e alimentação foram analisadas, em casa de vegetação, um híbrido e dezenove espécies do gênero Eucalyptus, três do gênero Corymbia e cinco mirtáceas nativas (Hexaclames edulis, Marlieria edulis, Plinia trunciflora and Psydium sp.). As maiores populações de C. spatulata ocorreram em E. robusta e E. pellita. No entanto, foram as espécies E. grandis e E. resinifera que apresentaram o maior número de plantas com sintomas de danos. As espécies E. cinerea, E. cloeziana, E. dunnii, E. benthamii, E. nitens, E. viminalis, E. pilularis e E. camaldulensis não apresentaram infestação por C. spatulata. Nas espécies de Corymbia foi observado um número muito reduzido de ovos de C. spatulata em C. citriodora e C. torelliana. Em nenhuma das espécies de Myrtaceae nativas foram observados ovos ou ninfas de C. spatulata. O número de ovos na planta foi altamente correlacionado com o número de ninfas, sugerindo que a contagem de ovos possa ser usada como uma ferramenta viável no monitoramento desta praga.

Palavras-chave: Pragas exóticas; pragas florestais; psilídeo.

About 5.4 million hectares of plantation forests are grown in Brazil for timber, pulp, paper, charcoal, fuel, rubber, vegetable oil, resin, tannin, and livestock shading. Although many different tree species are grown, the eucalypt is the predominant tree, comprising about 62% of the plantation. The most widely cultivated species are Eucalyptus grandis, E. urophylla, E. saligna, E. tereticornis, E. camaldulensis, E. viminalis, and Corymbia citriodora.

Many native insects have become serious pests in eucalypt plantations, probably because they have switched from native Brazilian Myrtaceae plants to eucalypts (Mariconi 1956). By 1962, 98 insect species had been reported from eucalypts in Brazil (Silva et al. 1968). The first insect pest in eucalypt plantations in Brazil was reported five years after the initial eucalypt research program was launched. There are reports of many native insect pests on eucalypts, including leaf-cutting ants, caterpillars, leaf-eating beetles, and termites (Andrade et al. 2000).

In addition to these native pests, several Australian pests have been introduced into South America and established in the eucalypt plantations. The most notable of these are the weevils (Curculionidae), Gonipterus scutellatus Gyllenhal and G. gibberus (Boisduval), which were introduced into Argentina in the mid-1920's, probably from apple fruits. They were subsequently found on eucalypts in the southern Brazilian state of Rio Grande do Sul and have progressively spread throughout the country to become serious defoliators (Freitas 1991; Anjos & Majer 2003). Another congeneric pair of pests are the wood boring cerambycids, Phoracantha semipunctata (Fab.) and P. recurva Newman. The former species was introduced in the early 1950's and both have rapidly spread throughout the country (Biezanko & Bosq 1956; Baucke 1957). They bore into the trunk and can cause 15-20% reduction in wood production (Acel 1984).

One of the most recent pest introductions is the psyllid Ctenarytaina spatulata Taylor, which was first detected in Brazil in 1994, found on drought-affected sprouts of Eucalyptus grandis in a plantation located in the northern part of Paraná State (Burckhardt et al. 1999; Santana et al. 1999, 2005; Andrade et al. 2000; Santana & Zanol 2006). This insect had previously been introduced into New Zealand without its natural enemies, causing serious damage to Eucalyptus (Symphyomyrtus) species, mainly in the Transversaria, Maidenaria and Exsertaria sections (Taylor 1997; Satchell 1999). The damage caused by this psyllid in New Zealand has become increasingly apparent over the last few years, with symptoms such as deformation and premature leaf shedding and production of substrate for sooty mould on branches and leaves (D. Satchell pers. comm.). During summer, moderate attacks in the northern New Zealand can cause senescence and premature leaf shedding, with consequent thinning of the crown. The winter shoots suffer less attack, with some distortion and staining due to the growth of sooty mould. It is thought that C. spatulata may also contribute to the loss of vigor of the trees in New Zealand (Satchell 1999). Ctenarytaina spatulata has also been recorded from California in the USA, Uruguay (Taylor 1997), Portugal and Spain (Hollis 2004; Valente et al. 2004).

In view of the economic importance of eucalypts in Brazil, the recent introduction of C. spatulata is of considerable concern. Therefore, this study was undertaken to elucidate the preference of C. spatulata for various eucalyptus species by examining oviposition and infestation rates of summer and winter generations. We also examined the potential of this psyllid to infest selected native Brazilian myrtaceous species, since the existence of plants from the same family as Australian eucalyptus might predispose them to the attack by this psyllid species.

This research was undertaken in a greenhouse at Embrapa-Florestas, in Colombo, state of Paraná, during 2000 and 2001, under average winter temperatures (27.2ºC, 15.3ºC and -0.6ºC) and summer temperatures (32.7ºC, 20ºC and 9ºC).

Experiment 1. A range of 17 Eucalyptus species, one Eucalyptus hybrid (Cambiju) and two Corymbia spp. seedlings (Table I) were produced in plastic tubes (50 ml) during the summer 2000. Ten seedlings of each species were numbered and sprayed with 0.1% sodium hypochlorite and randomly displayed inside four frames per cage, 50 seedlings per frame, and left in a nutrient solution, as described by Sarruge (1975). Solution concentration was nitrogen (225 ppm), phosphorous (31 ppm), potassium (234 ppm), calcium (200 ppm), magnesium (48 ppm), sulphur (64 ppm), borum (0.5 ppm), Manganes( 0.5 ppm), zinc (0.05 ppm), cupper (0.02 ppm), molibdenium (0,01 ppm), and iron (5-0 ppm). Nutrient solution was replaced weekly. Seedlings were exposed to C. spatulata by placing two terminal shoots of field-collected E. grandis (infested with a mean of 3.1 nymphs and 1.2 eggs) next to each plant. Seedlings were placed in four cages of voil and evaluated 180 days after initial exposure, when C. spatulata population was well established (winter 2000), counting the number of eggs and nymphs on one terminal shoot of each plant.

Experiment 2. During the 2000 winter a slightly different range was seen in plants seedbed with vermiculite, being those: 17 Eucalyptus species, plus one hybrid Eucalyptus (Cambiju), two Corymbia species and four native Myrtaceae species (Table I). Seedlings were subsequently split up and transferred to plastic-bag pots. These were mounted in frames over trays of nutrient solution as in Experiment 1. Individual seedlings were exposed to C. spatulata by placing an infested terminal shoot of E. grandis (infested with a mean of 3.1 nymphs and 1.2 eggs) next to each seedling. At the end of the experiment (summer 2001 on 19 February 2001, 180 days after initial exposure to C. spatulata), the apical terminal shoot of each plant was removed and eggs and nymphs were counted. Number of plants with deformities and black sooty mould on leaves were also scored.

The numbers of eggs and nymphs on each plant species, for the winter and summer generations respectively, were separately compared by one-way analysis of variance and the individual means were compared by Duncan's post-hoc test using a 5% significance level. Based on this analysis, the plant species were classified in four categories: "most preferred", "preferred", "not preferred" and "less preferred". To ascertain whether incidence of eggs transcribed into infestations of nymphs, the two variables were subjected to regression analysis and the Pearson correlation coefficient was calculated.

Numbers of eggs and nymph colonies were larger in the winter. There was a strong linear relationship between number of eggs and nymphs on various seedlings species both, during the winter season (r = 0.79; n = 13; P < 0.05) and summer (r = 0.95; n = 15; P < 0.05). Less preferred plants with few or no eggs or nymphs were not included in the analysis (Fig. 1). It was observed that C. spatulata oviposits preferentially on the most suitable host plants. The Duncan's test was used to classify the plant species based on the preference degree by the psyllids. These classifications are not strict, but rather are meant as a convenient way of describing the results of insect preference.

In both generations, E. robusta was the most preferred plant species for infestations, and the only one classified as most preferred. Similarly, in the two experiments E. pellita, E. urophylla, E. grandis, and the Cambiju hybrid were classified as preferred. E. deanei, E. microcorys, E. saligna, E. tereticornis were not preferred, whereas E. dunnii and E. pilularis were the less preferred. The positions of the remaining species varied between the winter and summer generations (albeit minimally) in the classification; E resinifera reclassified from not preferred to preferred, while E. camaldulensis, C. citriodora, E. cloeziana, E. nitens and E. viminalis switched from not preferred to less preferred between seasons. Note that C. maculata, C. torelliana, E. benthamii, E. cinerea, E. paniculata were subject to experimentation in only one of the seasons (Table I). None of the native Myrtaceae was infested by the psyllid.

Plants infested with C. spatulata did not show visible symptoms of attack. In the winter generation, E. robusta, which was the most preferred species, showed intermediate levels of staining and curling leaves and sooty mould. On the other hand, E. grandis and E. resinifera showed more attack symptoms, even being lower on the preference scale. E. alba also exhibited moderate symptom levels, even though it was classified as not preferred.

Neither eggs nor nymphs of C. spatulata were found on any of the native species of Brazilian Myrtaceae studied. We believe that in view of their taxonomic spread, there is a low probability that C. spatulata will adapt to non-eucalyptus hosts.

Although Taylor (1997) commented that C. spatulata has a wider host range than other members of the genus, their host range was still limited to a modest number of eucalyptus species in certain sections and subgenera of Eucalyptus and Corymbia. In this study, host plants that showed the highest levels of infestation by C. spatulata are members of the Eucalyptus subgenus Symphyomyrtus, mainly in the section Transversaria. By contrast, hosts in the Eucalyptus subgenus Symphyomyrtus, sections Adnataria, Exsertaria, Maidenaria and some Transervaria, the subgenera Idiogenes and Monocalyptus and the genus Corymbia were classified either as not preferred or less preferred.

These results indicate that several eucalypt species are potentially vulnerable to C. spatulata, although infestation levels do not necessarily transcribe into visual symptoms. However, absence of symptoms does not mean lack of importance of the insect, as the vigor of the tree might be reduced by the psyllid.

Damage may be particularly associated with drought-affected shoots, at least for E. grandis (Burckhardt et al. 1999; Santana et al. 1999, 2005; Andrade et al. 2000; Santana et al. 2003). When considering the role of chemical present in the leaves infested with Psyllidae, White (1971) proposed that plants stressed by lack or excess of water cease to grow and, consequently, accumulate nitrogen in terminal shoots. The subsequent increase in the source of soluble nitrogen associated with the stress of the host plant increase the survival of the nymphs and may explain the observations concerning C. spatulata on E. grandis in Brazil (Catling 1969; White 1969). According to these data, we believe that the plants here considered most preferred can be more severely attacked in conditions of more severe water stress.

Amongst the host species evaluated in this study, there are some that are very important to the Brazilian forestry sector, including extensively planted monoculture areas of E. grandis and E. urophylla. Continuous plantations of such species may encourage the dispersal of C. spatulata. Additionally, this pest is associated with leaf senescence and drying of terminal shoots of at least one eucalyptus species, requiring control measures following an integrated pest management program.

The statistical coefficients between eggs and nymphs (Fig. 1) indicate that immature populations can be estimated by egg numbers. The resulting information might be used to determine if either prophylactic or curative treatments were required. Alternatively, not preferred or less preferred eucalyptus species could be planted, reducing the need for active control of this pest. Candidate species might include the one that showed lower infestation levels, such as E. benthamii, E. dunnii, E. cinerea, E. cloeziana, E nitens, E. paniculata, E. pilularis, E. viminalis, C. citriodora, C. maculata and C. torelliana, or even those showing medium-low infestation levels, such as E. alba, E. camaldulensis, E. deanei, E. microcorys, E. saligna, E. resinifera, and E. tereticornis.

Acknowledgements. To the Brazilian Embrapa-Florestas for providing facilities and human resources; to Gary Taylor kindly commented on an earlier draft of this manuscript. This work is a part of a doctorate thesis which was submitted to the Universidade Federal de Paraná in Curitiba.

Received 30/09/2008; accepted 30/12/2009

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Publication Dates

• Publication in this collection
  07 May 2010
• Date of issue
  Mar 2010

History

• Accepted
  30 Dec 2009
• Received
  30 Sept 2008