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Predation Efficiency of Insect Predators in Suppressing Red Mite, Tetranychus Bioculatus Attacking Marigold

M.A. TALEB
School of Agriculture and Rural Development, Bangladesh Open University, Gazipur, Bangladesh

M.A. SARDAR
Department of Entomology, Bangladesh Agricultural University, Mymensingh, Bangladesh

Abstract/ Executive Summary:

Experiments were conducted to find out the efficiency of predators, Stethorus punctillum and Micraspis discolor in searching (behaviour), handling (time) and predating (efficiency) red mite, Tetranychus bioculatus (Wood-Mason) attacking marigold plants. Predators grub and adults spent their time through walking, running and flying for searching prey. The walking was common in both the stages and it was more common in S. punctillum than M. discolor. The grub and adult of S. punctillum were more active than that of M. discolor for searching prey. The handling times were measured by adding time required for recognition, capture and consumption of the prey. The predators recognized prey in 2.2-3.0 minutes after release. The capture and consumption time differed significantly. The study showed significantly different preying activity of predators on egg, larva, nymph and adult of red mite. The predating efficiency of S. punctillum and M. discolor was significantly higher when feeding on eggs and was ranged from 35.4 to 48.4 eggs per day than that of larva, nymph and adult of the mite. The rate of consumption of red mite by S. punctillum and M. discolor increased with increasing density of mite up to 30 mites and was correlated with its population density.

Keywords: Predation , Stethorus punctillum, Red mite, Marigold.

Location: Department of Entomology of Bangladesh Agricultural University (BAU), Mymensingh

Start Date: 00-11-2005

End Date: 00-03-2006

Program Area: Pest Management

Commodity: Predator

Objectives:

To evaluate the biotic potential of insect predators, S. punctillum and M. discolor in suppressing red mite, T. bioculatus attacking marigold plants.

Methodology:

The study utilizing Stethorus punctillum and Micraspis discolor for suppressing red mite was conducted in the laboratory of Department of Entomology of Bangladesh Agricultural University (BAU), Mymensingh between November, 2005 and March 2006. To ensure supply of the predators for the study the grubs of S. punctillum and M. discolor were cultured in the laboratory. Adult adult beetles of the predators were collected from the marigold plant infested with red mite, Tetranychus bioculatus from the marigold garden of Bangladesh Agricultural University (BAU). Red mites were provided as food for mass culturing of the predators. The beetles were kept as single pair (male and female) in ten Petri dishes (9.0 cm x 1.5 cm) for mating. Everyday field collected mites with infested marigold leaves were supplied in the Petri dishes as food for the predators. The observations were made at two times daily to examine oviposition of the beetles. Female predators laid yellow spindle shaped eggs in masses on the supplied leaves and surrounding wall of the Petri dishes. The eggs were kept undisturbed in the Petri dishes for hatching. After hatching eggs, newly emerged larvae were transferred to ten Petri dishes (14.0 cm x 1.5 cm) with the help of a camel hair brush (00) and reared on red mites until adult emergence. Each Petri dish contained 10-15 grubs each of S. punctillum and M. discolor. Mites were supplied as food for the grub of the predators as described earlier.. The Petri dishes were kept undisturbed during the pupation of the grub of predators. The newly emerged beetles were placed in other Petri dishes of the same size allowing one male and one female for successful mating and laying eggs. Red mites were supplied to the new adults everyday in the same manner as indicated. The procedure was continued to ensure required number of adult predators for subsequent studies. Searching Behaviour of Predator Grub and Adult Forty prey (adult red mite) were placed in Petri dish on the marigold leaves and allowed to settle and fed in each replicate of the experiment. Mites quickly moved from the base to the apex of the leaves where they started feeding. Forty adults of red mites released in the centre, along the edge, apex, between apex and centre and at base of marigold leaf in Petri dish and a single predator grub or adult of S. punctillum and M. discolor was released in different leaf positions in the Petri dishes and allowed to search prey feeding on various portion of the leaves. Searching by predators was observed in respect of searching path and the handling time (recognition time, capture time and consumption time) for the predator and recorded. The procedure for recording prey and predator behaviour was followed as described by Wratten (1973). Consumption of Immature Stages of Red Mite by Predators Fifty eggs, larvae and nymphs of the mite were placed separately per replicate (five replicates) on marigold leaves in the Petri dishes (9.0 cm x 1.5 cm) and a single predator of the required stage was then allowed to feed immature stages of mite. The number of mites increased or decreased was then observed in each replicate at 24 hours of predator release. Functional Response of Predators To study the functional response of predators, S. punctillum and M. discolor, the experiments was conducted on marigold plants raised in earthen pot. The study was based on different population densities of red mite as prey attacked by fixed/single number of grub and adult of predators. The method followed was that of Tamaki and Long (1978). Five grubs of predators one in single marigold plant caged with 10, 20, 30, 40 and 50 number of mite. Each treatment was replicated five times and one marigold plant considered as a replicate. The same procedure was followed for the adult predators. Caging was made for covering the whole plant by nylon net. The cages with mite were kept free from other predator before treatment. The observations were made on the number of mites increased or decreased in each treatment at 24, 48 and 72 hours of predator release. Small quantity of vaseline was applied around the base of the marigold plants which received predator grub to avoid its escape from the caged plant. The experiment was laid out following Completely Randomized Design (CRD). The number of mites were counted in leaves, stems and twigs of the plant at 24, 48 and 72 hours of predator release. During the study room temperature was recorded in the laboratory by using dry and wet thermometer. Data obtained from the study were analyzed using computer software for one factor analysis following CRD and means were separated by Duncan’s Multiple Range Test (DMRT).

Source of Information: J Agric Rural Dev 5(1&2), 98-104, June 2007 ISSN 1810-1860

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Achievement/Findings:

The study showed significantly different preying activity of predators on egg, larva, nymph and adult of red mite. The predating efficiency of S. punctillum and M. discolor was significantly higher when feeding on eggs and was ranged from 35.4 to 48.4 eggs per day than that of larva, nymph and adult of the mite. The rate of consumption of red mite by S. punctillum and M. discolor increased with increasing density of mite up to 30 mites and was correlated with its population density.

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