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Effect of Insecticidns on the Microbial Flora of Phyllospher.e and Rfiizosphere of Leguminous Plant

K. Alam
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

M. M. Chowdhury
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

S. Haque
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

M. S. A. Hossain
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

A. Islam
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh.

Abstract/ Executive Summary:

A pot culture experiment in net house with Dhaincha (Sesbania aculeata, L) was carried out to study the microbial population of both phyllosphere and rhizosphere. The insecticide diazinon was used for phyllosphere keeping in view a range of apprication varying from 0.05 to 0.35 % (of the insecticide and that dieldrin was used for rhizosphere in the range of 0.25 to 1.75%. It was found that diazinon decreased the number of bacteria, actinomycetes and fungi as revealed by both plate and MPN counts. The effect was also found to be pronounced during the first fortnight of application and less conspicuous at the later period. As for dieldrin application, the number of bacteria and actinomycetes remained unaltered whereas fungal population was found to increase slightly although the application of dieldrin was at a higher concentration.

Keywords: Dhaincha, Fertilizer, Soil, Insecticides, Microbial flora

Location: Dhaka, Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Dhaincha

Objectives:

To determine the effect of insecticides on the microbial flora of phyllosphere and rhizosphere of Sesbania aculeata (Dhaincha).

Methodology:

In order to study the effect of insecticides on the microbial flora of both phyllosphere and rhizosphere, soil samples of Tejgaon series were collected from 0 to 15 cm depth. Five Kg soil was taken in each pot and kept exposed in net house. Each pot contained five plants. Different doses (0.05,0.10,0.15, 0.20,0.25,0.30 and 0.35%) of diazinon in constant volume were sprayed over the phyllosphere of 15 days old plants and at the same time constant volume of dieldrin of different doses (0.25, 0.50, 0.75, 1.00, 1.25,1.50 and 1.75%) were sprayed in the rhizosphere. Total microbial (bacteria, actinomycetes and fungi) counts of both phyllosphere and rhizosphere were determined by MPN counting technique (6) at specific intervals upto 75 days of plant growth.

Source of Information: Dhaka University Studies B, 72, 1985

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Organophosphorus insecticides were known to affect oxidative phosphorylation (4). Depression of microbial growth by organophosphate insecticides was due probably to inhibition of oxidative metabolism (9). Inhibition of growth of microbial flora by the organoposphate insecticide ‘diazinon’ 11 the present investigation may be responsible for the increase of residual phosphate in the phyllosphere which affect oxidative phosphorylation and oxidative metabolism. The toxicity of diazinon was due to the residual effect of phosphate but dieldrin by its durable nature showed no toxic effect to microbial flora except for fungi. On the other hand, dieldrin produced stimulatory effect on the growth of saprophytic fungi. The effect was also found to be pronounced during the first fortnight of application and less conspicuous at the later period. As for dieldrin application, the number of bacteria and actinomycetes remained unaltered whereas fungal population was found to increase slightly although the application of dieldrin was at a higher concentration.

Knowledge Management: Journal