Efficacy of Beauveria bassiana (Bals.) Vuill. against the spruce bark beetle, Ips typographus L., in the laboratory under various conditions |
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Authors: | J Kreutz O Vaupel G Zimmermann |
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Institution: | Federal Biological Research Centre for Agriculture and Forestry, Institute for Biological Control, Darmstadt, Germany;;HESSIAN FOREST –Service Centre for Forest Management, Information and Forest Research, Hann. Münden, Germany |
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Abstract: | Abstract: In laboratory bioassays, the efficacy of the entomopathogenic fungus Beauveria bassiana against the spruce bark beetle, Ips typographus , was tested under various conditions. Four of the tested isolates and the commercial product Boverol® caused 99–100% mortality when tested at a concentration of 1.0 × 107 conidia/ml at 25°C. Using B. bassiana isolate 138 at a concentration of 1.0 × 106, the median survival time (MST) was 6.1 d and significantly longer compared with the MST of 4.2 and 4.0 d at 1.0 × 107 and 1.0 × 108 conidia/ml, respectively. In the next experiment, the beetles were maintained on spruce bark, filter paper or artificial diet during the bioassay with Boverol®, and significant differences in the MST of 3.6, 2.5 and 5.3 d, respectively, were noticed. The experiment with Boverol® at different temperatures showed that the beetles lived significantly longer at 15°C (MST 8.7 d) than at 20, 25, 30 and 35°C. At 25°C, the beetles died most rapidly (MST 3.5 d). At different relative humidities (RH) of 40, 70 and 100%, nearly all beetles were dead after treatment with a suspension of Boverol® at 1.0 × 107 conidia/ml. At 40% RH, 49% of the untreated beetles died after 7 d. The best effects were achieved with the following bioassay: beetles were fed for three days on artificial diet, then dipped into a solution of 1.0 × 107 conidia/ml and transferred on a piece of spruce bark in Petri dishes at 25°C and 70% RH. |
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Keywords: | Ips typographus Beauveria bassiana bioassay biological control Boverol® |
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