Preliminary Survey of the Occurrence of Entomopathogenic Nematodes and Fungi in the Forest Soils of Algeria

摘要

The natural distribution and diversity of entomopathogenic nematodes (EPN) and fungi (EPF) in various biotopes in Algeria was studied, particularly in forests and plantations of cedar, oak, pine, eucalyptus and palm. The objective of this study was to identify EPN and/or EPF species which could be used to control forest insect pests. Soil sampling was carried out at 223 sites from April 2007 to March 2008. To trap EPN's juvenile larvae of Steinernematidae and Heterorhabditidae and EPF, the method of "insect-trap" was used in the laboratory. Caterpillars of Galleria mellonella (Lep., Pyralidae) and the forest insects Thaumetopoea pityocampa (Lep., Thaumetopoeidae) and Lymantria dispar (Lep. Lymantriidae) were used. The presence of EPN was noted in 8.1% of the sampled sites and EPF in 9.9%. The presence of the EPN in the oasis biotope may result from particular microclimate conditions (of temperature and humidity). Nematodes belonging to the Steinernematidae family and Steinernema genus were identified. In addition, 10 fungal species were isolated, namely: Beauveria bassiana, Fusarium sp., Alternaria sp., Penicellium sp., Trichoderma sp., Sordaria sp., Mucor sp., Chaetomium globosum, Aspergillus nigricans and Rhizopus nigricans. The majority of the fungi were isolated in the conidian form, except for Chaetomium globosum which had its perfect form with perithecia. The presence of EPN and EPF seems to depend on the dominant species of forest trees, either cork oak (35%), cedar (12.5%), pine (12.5%), palm (10%) or eucalyptus (7.5%). Key words: Entomopathogenic; nematodes; fungi; forest insect pests; biological control; Algeria Prospe??o Preliminar de Nemátodos e Fungos Entomopatogénicos em Solos Florestais da Argélia Sumário A distribui??o natural e a diversidade de nemátodos e fungos entomopatogénicos em vários biótipos da Argélia foram estudadas, incidindo particularmente em florestas de cedro, carvalho, pinheiro, eucalipto e palmeiras. O objetivo do estudo foi identificar nemátodos e/ou fungos que possam vir a ser utilizados em futuros programas de controlo biológico de pragas florestais. Amostragens de solo foram efetuadas em 223 locais da Argélia, entre Abril de 2007 e Mar?o de 2008. Para capturar os nemátodos e fungos foi utilizado o método do "inseto-armadilha" do "inseto-armadilha", usando-se como isco lagartas de Galleria mellonella (Lep., Pyralidae), Thaumetopoea pityocampa (Lep., Thaumetopoeidae) e Lymantria dispar (Lep. Lymantriidae). Detetou-se a presen?a de nemátodos entomopatogénicos em 8,1% dos locais amostrados e de fungos em 9,9%. A presen?a destes organismos em oásis pode derivar de características micro-climáticas particulares, nomeadamente de temperatura e humidade. Foram identificados nemátodos pertencentes à família Steinernematidae e ao género Steinernema, e cerca de 10 espécies de fungos, nomeadamente: Beauveria bassiana, Fusarium sp., Alternaria sp., Penicellium sp., Trichoderma sp., Sordaria sp., Mucor sp., Chaetomium globosum, Aspergillus nigricans e Rhizopus nigricans. A maioria dos fungos foi isolada como conídios, excepto Chaetomium globosum que apresentou a forma perfeita com peritecas. A presen?a dos nemátodos e fungos parece estar dependente do coberto florestal dominante, seja ele sobreiro (35%), cedro (12,5%), pinheiro (12,5%), palmeira (10%) ou eucalipto (7,5%). Palavras-chave: Entomopatogénico; nemátodos; fungo; pragas florestais; controlo biológico; Argélia Introduction During the last ten years, great efforts toward the increase and protection of forest trees in nurseries and agro-forestry plantations have been made in Algeria. To support these efforts, phytophagous insect pests must be controlled in young reforestation and also in nurseries. More than 100 000 hectares of reforestation and natural forests have been treated yearly against the principal defoliating forest insect pests, such as Thaumetopoea pityocampa (Lep. Thaumetopoeaidae), Lymantria dispar (Lep. Ly