The Selecting Of The Entomogenous Fungus, Beauveria Bassiana On Dendrolimus Tabulaeformis In North Dry Area

Pine caterpillar, Dendrolimus (Lepidoptera : Lasiocampidae) is a kind of great injurious pest to pine forest in China. Beauveria as the disease-producing germ is often used to control these pests in south part of China. But it is limited in north part of China, because of the climatic characteristics such as less rain, dry and lower temperature. This thesis is to study the pathogens of pine caterpillar in north China The disease-producing germ was obtained from the larval illness corpse of Dendrolimus tabulaeformis Tsai et Liu which was collected from the pine forest of Lingqiu County, Shanxi Province, during 2001-2003. The results showed as following:1. Through isolation, culture and observation, the disease-producing germ was identified as Beauveria bassiana, belongs to the genus, Beauveria in the order, Hyphomycetes, the class of Hyphomyceres and the subphylum Deuteromycotina. Its morphological characteristics were described.2. Some biological characteristics were known on the entomogenous. Its growth rates were 4.12mm/d, 3.77mm/d and 1.99mm/d when the cultural temperatures were respectively set at 26 ± 1℃, 15 ± 1℃ and 7 ±1℃. The bourgeon rate of its spores was 100%.3. The germ solution in five different concentrations was tested to infect the larvae of Dendrolimus tabulaeformis in the stages of 1 - 4 instar. The result showed that at 25℃ and the relative humidity of (95± 5 ) %, the mortalities of the larvae appear the supreme and theLT50 is the lowest. The two concentrations 5× 10 and 1 × 10 spores/ml caused the most mortality of the larvae in the 5 concentrations tested. Therefore, the concentration of 1 × 108 spores/ml was recommended for controlling the pest in practice.