Natural efficiency of parasitism by Billaea rhynchophorae (Blanchard) (Diptera: Tachinidae) for the control of Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae)

Eficiência do parasitismo natural por Billaea rhynchophorae (Blanchard) (Diptera: Tachinidae) para o controle de Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae)

SCIENTIFIC NOTE

Natural efficiency of parasitism by Billaea rhynchophorae (Blanchard) (Diptera: Tachinidae) for the control of Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae)

Eficiência do parasitismo natural por Billaea rhynchophorae (Blanchard) (Diptera: Tachinidae) para o controle de Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae)

José Inacio L. Moura^I; Ronaldo Toma^II; Ricardo B. Sgrillo^III; Jacques H.C. Delabie^IV

^IEstação Experimental Lemos Maia / CEPLAC, 45690-000 Una, BA, [e-mail]

^IIMuseu de Zoologia, USP, Avenida Ipiranga, 481, C. postal 42694, 04299-970 São Paulo, SP

^IIISeção de Métodos Quantitativos

^IVUnidade de Pesquisa Associada Laboratório de Mirmecologia, Convênio UESC-CEPEC, [e-mail]. CEPEC/CEPLAC, C. postal 7, 45600-000 Itabuna, BA

ABSTRACT

The occurrence of the tachinid parasitoid Billaea rhynchophorae (Blanchard) on larvae of the palm weevil Rhynchophorus palmarum (L.) was evaluated in plantations of piassava palm (Attalea funifera Mart.) and African oil palm (Elaeis guineensis Jacquin), in southeastern Bahia, Brazil. The monthly percentages of parasitism were evaluated during 13 months, from November 2000 to November 2001, based on the comparison between the number of parasitized and non-parasitized cocoons of R. palmarum. Mean parasitism was 40% and ranged from 50% in November 2000 to 18% in July 2001. While there is no method of mass reproduction of the parasitoid, a simple management practice is recommended, in order to preserve its beneficial effects in palm plantations.

Key words:Attalea funifera, Elaeis guineensis, palm tree, Bursaphelenchus cocophilus, red ring disease

RESUMO

Foi avaliada a ocorrência do parasitóide Billaea rhynchophorae (Blanchard) em larvas de Rhynchophorus palmarum (L.) em plantações das palmeiras piaçava (Attalea funifera Mart.) e dendê (Elaeis guineensis Jacquin) no Sudeste da Bahia. As porcentagens mensais de parasitismo foram determinadas durante 13 meses, entre novembro de 2000 e novembro de 2001, comparando-se o número de casulos de R. palmarum parasitados e não-parasitados. O índice médio de parasitismo foi 40%, variando de 57% em novembro de 2000 a 18% em julho de 2001. Enquanto não existe método de criação massal do parasitóide, recomenda-se uma prática simples de manejo que visa a preservar seu efeito benéfico nas plantações de palmeiras.

Palavras-chave:Attalea funifera, Elaeis guineensis, palmeira, Bursaphelenchus cocophilus, doença do anel vermelho

The palm weevil Rhynchophorus palmarum (L.) is one of the most important pests of coconut and African oil palm in Tropical America causing relevant economic damages (Bondar 1940; Franco 1964; Ferreira et al. 1998, 2002). This insect is the main vector of the red ring disease caused by the nematode Bursaphelenchus cocophilus (Cobb). Many researches have been carried out (Bondar 1940, Franco 1964, Morin et al. 1986) in order to find more efficient ways of controlling R. palmarum. Among the reports on the use of natural enemies aiming at the biological control of the beetle, there are references in the literature on the fungus Beauveria bassiana (Balsamo) Vuillemin and the parasitoid tachinid Billaea menezesi (Guimarães) (formerly Paratheresia menezesi) (Diptera: Tachinidae) (Moura et al. 1993, Ferreira et al. 2002). The other tachinid Billaea rhynchophorae (Blanchard) was reported by Guimarães (1977a, 1977b) as a parasitoid of R. palmarum, but, according to Murphy & Briscoe (1999), no recent study has been reported on this fly.

Observations on piassava, Attalea funifera Mart, and African oil palms, Elaeis guineensis Jacquin, were carried out in palm plantations at Una and Canavieiras, Bahia State, Brazil. Twenty cocoons of R. palmarum were collected monthly in A. funifera and another 20 in E. guineensis, all on plants infected with the red ring disease in advanced stage of decomposition. Percent parasitism was calculated as the ratio between the number of parasitized and non-parasitized cocoons of R. palmarums. We considered as non-parasitized cocoons those that presented inside living imago, larvae or pupae of R. palmarum, and as parasitized those with larva, exsuviae, puparia or rests of puparium of B. rhynchophorae.

Mean parasitism of B. rhynchophorae on R. palmarum was 40% (Fig. 1). The results showed a reduction in the percentage of parasitism during winter probably linked to the increase of precipitation in May and June as well as a reduction of temperature.

Mass rearing and release of B. rhyncophorae for the control of R. palmarum is not possible yet because the biological cycle of the former species is unknown. However, in order to protect this parasitoid we suggest that large amounts of cocoons of R. palmarum should be collected and placed in screening cages in which the mesh size would allow the tachinid flies to escape while the non-parasitized hosts are retained.

Received 23/I/04. Accepted 18/VI/05.

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Publication Dates

• Publication in this collection
  10 July 2006
• Date of issue
  Apr 2006

History

• Accepted
  18 June 2005
• Received
  23 Jan 2004