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Control of Two–spotted Spider Mite Tetranychus Urticae Koch (acari: Tetranychidae) by Some Selected Chemicals

S. Hossain
Department of Zoology, University of Rajshahi, Rajshahi

M. M. Haque
Department of Zoology, University of Rajshahi, Rajshahi

N. Naher
Department of Zoology, University of Rajshahi, Rajshahi

Abstract/ Executive Summary:

The experiment was conducted to study the effectiveness of four commonly used chemicals viz., deltamethrin, cypermethrin, malathion and sulphur against two-spotted spider mite (TSSM), Tetranychus urticae Koch on potted bean plants and on excised leaf discs. Mite population remained significantly lower in all treated plots except malathion treatment. The population of T. urticae differed significantly due to different chemicals and it remained lower up to 4th week on single-sprayed plants, which again increased. But in double-sprayed plants mite population was checked and remained significantly lower. The estimated LD₅₀ values for cypermethrin, malathion, deltamethrin and sulphur were 2.9956, 15.8663, 0.5386 and 20.7045 nl.cm-2 respectively when the chemicals were sprayed before mite release. But the LD₅₀ values for these chemicals sprayed after mite release were estimated 1.8110, 8.2746, 0.2192 and 6.8308 nl.cm^-2. The use of chemicals is essential for better yield of crops. Among the four tested chemicals the pyrithroids (cypermethrin and deltamethrin) were found more effective against the TSSM than the other two.

Keywords: Two-spotted spider mite, Tetranychus urticae, Bean, Malathion, Sulphur

Location: Rajshahi

Start Date:

End Date:

Program Area: Pest Management

Commodity: Insects

Objectives:

The present investigation was aimed at studying the effectiveness of four selected insecticides namely, deltamethrin, cypermethrin, malathion and sulphur against TSSM on potted bean plants and the toxicity of these chemicals on this pest on excised leaf discs.

Methodology:

Control of T. urticae by chemicals on potted bean plants was conducted in the premises of the Laboratory of Ecology, Department of Zoology, Rajshahi University. For this purposes twenty clay-made pots (30×50 cm) with bean plant were maintained. All the twenty pots were arranged in 10 groups taking two in each. Among these eight were selected for chemical treatment, one for control and the remaining one for mass culture of TSSM. Every group was placed separately and covered with fine net to protect from the natural infestation. Bamboo sticks were used to support the bean plants. Infestation: After two months of sowing when the bean plants grew enough, they were infested by TSSM. TSSM used for infestation were collected from the Integrated Pest Management (IPM) laboratory, Institute of Biological Sciences, Rajshahi University. Ten adult females were released on each bean plant. Placing the infested plant parts on leaf at the height of 0.75 m made release of the mites. Spray: Four selected insecticides viz., deltamethrin, cypermethrin, malathion and sulphur were tested against T. urticae. Two groups selected for each chemical, was again separated for single spray and double sprays where insecticide was sprayed once after two week of mite infestation on single spray grouped plant and the insecticide was sprayed twice on the double-sprayed grouped plants. On these plants, first spray was done after two weeks of infestation and second spray after four weeks of infestation. The dilution of insecticides and amount were maintained as prescribed by their distributors. No chemicals were sprayed on control and culture plants. Counting: Counting of mites was started from the first week of infestation. Fifteen leaflets were collected from each group of plants that were selected randomly. Total number of adult and mature mites was recorded. The counting was made every week on all the nine groups of plants and continued till twelve weeks after infestation. The effectiveness of the selected chemicals against T. urticae was done on excised leaf discs. This test was conducted in two ways: (1) solution was sprayed on leaf discs before mite release, and (2) solution was sprayed after mite release. This method was based on the surface film technique devised by Busvine (1971). For this purpose 1.5 cm² leaf discs were made from fresh bean leaf. The discs were checked under microscope for mites other insects. Then the discs were placed in petridish having a water soaked cotton bed. The chemicals were serially diluted with water. Fixed volume (0.1 ml) of chemical solution was dropped on each leaf disc and allowed to dry for five min at room temperature. Ten adult TSSM were transferred to each disc with the help of a fine brush. The chemicals were tested against the mites.

Source of Information: Univ. j. zool. Rajshahi Univ. Vol. 25, 2006. pp. 15-18

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The present experiment was done in two different ways. In addition to a control experiment, insecticides were applied on potted bean plants. Here deltamethrin exhibited more effectiveness against T. urticae than cypermethrin.

Knowledge Management: Journal