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In Vitro Evaluation of Contact Fungicides Against Beauveria Bassiana (bals) Vuill. Pathogenic to Silkwrom, Bombyx Mori L.

M.K. Pasha
Senior Research Officer
Bangladesh Sericulture Research and training Institute (BSRTI), Rajshahi.

M.S. Alam
Department of Botany, Rajshahi University

Abstract/ Executive Summary:

Beauveria bassiana (Bals) Vuill is the most virulent pathogen of white muscardine disease of silkworm, Bombyx mori L. White muscardine disease is prevalent in all.the sericultural countries of the world and cocoons production losses by this disease varies from 5 to 50 percent. (Jayaramaiah et al 1986). In Bangladesh this disease is also common during pre winter (October-November) and post winter (February-March) seasons as the low temperature and humidity of these periods are congenial for normal growth of bassiana. The maximum incidence of 18.39 percent has been reported here (Pasha and Alam 1998). Sevaral attempts have been made to control white muscardine by application of chemicals and fungicides. Samson and Mummigutti (1779) detected a number of organic and inorganic acids and bases which proved to be anti muscardine. Krishnaprased et al. (1978) reported that application of Bavistin at 10 ppm inhibit the growth of bassiana. The use of Captan and Dithane-M45 have also been stressed by Samson et al. (1986) against white muscardine disease. However the knowledge and technology developed by a country are not sufficient and applicable for control the same disease in other countries, because there is a wide range of climatic variation.

Keywords: Fungicides, Bombyx mori, Beauveria bassiana.

Location: Bangladesh Sericulture Research and Training Institute

Start Date:

End Date:

Program Area: Pest Management

Commodity: Diseases

Objectives:

To evaluate the toxicity of five contact fungicides against bassiana in vitro under the climatic conditions of Bangladesh.

Methodology:

Five contact fungicivies, viz. Dithane-M 45. Macuprax 65 WP, Robral 50 WP, Cupravit 50, Wp and Antracol 50 WP, each with three concentrations, eg. 0.05, 0.2 and 0.5%, were tested against bassiana. Conidia of bassiana were taken from 10 days old culture tubes and conidial suspensions with 30-40 conidia per optical field of compound microscope were prepared in a mixture of 1% peptone and 2% glucose solutions. An equal volume of conidial suspensions and desired fungicide were taken on a groove slide separately for each concentration in two replications. Groove slides were then placed in the humid chamber for 24 hours at 25<->C in an incubator. The humid chamber consisted of a petridish of 90 mm in size with its lid. The inner wall of petridish and its lid was lined with sterilized filter paper which was then moistened with sterilized disitilled water. Over the moist filter paper two glass bars were placed which prevented groove slides coming in contact with the moisture of the filter paper directly. After the incubation period was over one drop of cotton blue was given on groove slide and then it was examined under the microscope. The average value of two replications were calculated for determining the conidial germination and to evaluate desired fungicides with dose against bassiana under in vitro condition. A control line was also maintained side by side for comparison. The results are presented in Table 1. Dithane-M 45 showed the complete inhibition of conidial germination at the highest concentration of 0.5% followed by Robral. The highest conidial germination (23.31%) was recorded at 0.05% of Antracol 50. Higher conidial germination were observed at lower concentrations by all the fungicides tested.

Source of Information: Bulletin of Sericulture Research. 1999 Vol.10:87-89 published by Bangladesh Sericulture Research and Training Institute.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Out of five contact fungicides, Dithane-M-45 at 0.5% produced zero conidial germination. The other two concentrations of the said fungicide were also found to be effective and only 6.31 and 2.36% conidial germination were recorded at 0.05 and 0.2% respectively. Robral 50 was also found to be effective. The other three fungicides Macuprax 65. Cupravit 50 and Antracol 50 only inhibited conidial germination at 0.5% substantially. Siddaramiah (1979) reported that Dithane M-45 at 0.05% was effective against bassiana, which is in agreement with the present study. The over all performanc of the contact fungicides against conidial germination in vitro was better as compared to the control. Before recommendation for application it requires further stud on silkworm directly.

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