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Exploring the Possibilities of Biological Control of Weeds by Phytophagus Insects

M. Shahjahan
Department of Entomology, Bangladesh Agricultural University, Mymensingh

A.A. Mamun
Department of Agronomy, BAU, Mymensingh

Abstract/ Executive Summary:

Insects feeding and taking Shelter on weeds of wheat, mustard, lentil, rice (aman, boro and aus) and jute were Identified. Large grasshoppers, chrysomelid beetles [Cassida enervis (Boheman), Galerucella grisescens (Joannis)], leaf beetles and black beetles were found to feed on weeds. The crop feeding and predatory insects which take shelter on different weeds were white backed plant hoppers, large grass hoppers, epilachna beetles, Cassida enervis, Galerucella qrisescens, leaf beetles, lady bird beetles, black beetles, rice green leaf hoppers, spiders, aphids, hispa and dragon flies. Various stages of the life cycle of Cassida enervis and Galerucella grisescens were studied. They are observed to be voracious feeder of the weed helencha, biskatali, gangpalong and nunia.

Keywords: Weeds, Insects, Host preference food consumption, Biology of chrysomelid beetles

Location: Department of Entomology, Bangladesh Agricultural University, Mymensingh

Start Date:

End Date:

Program Area: Pest Management

Commodity: Insects

Objectives:

1. To survey the weeds serving as alternate hosts for harmful insects of crops.

2. To identify the insects feeding and taking shelter on weeds.

3. To identify the host-specific weed feeding insects that will not attack the crop plant.

4. To study the biology, ecology, host-range and damage potential of weed feeding insects.

Methodology:

The insects species feeding on weeds, infesting both weeds and crops and taking shelter on weeds were observed visually in the rice (aman, boro and aus). mustard, wheat, lentil and jute crop fields. Regular observations at 15 days intervals and at different growth stages of the crop and weed were made to record pest incidence. Larval and adult stages were collected as they appeared to feed/take shelter on crop and weeds simply by hand and aerial net. In the laboratory, insects were identified on the basis of their morphological characters. For further confirmation rice plant and weeds of rice plants were grown in iron tray in all seasons. Insects were collected from rice fields and then released into the iron tray which was covered with iron net cage, Thereafter, the insects feeding and taking shelter on weed and crop plant were observed visually. For undertaking the biological studies of Chrysomelid beetle, various stages of the life cycle of Cassida enervis and Galerucella grisescens were studied under laboratory condition. Five pairs of newly emerged beetles for each case were released in the separate petridishes containing helencha (Jussieua repens), and gangpalong (Rumex maritimus) weed plants were allowed to lay eggs. The eggs were left undisturbed till their eclosion. About six hours of hatching, the hatchling from different eggs were distributed carefully in 10 (ten) pairs of petridishes (100 x 15 mm) for each insects at a constant density (10 larvae per pair of petridishes) to carry out their life processes in the usual way. Observations were made on pro-oviposition, oviposition, incubation, larval and pupal period.and adult longevity. A total of 29 plant species under 15 family for chrysomelid beetle and 19 plant species under 12 family for black beetle were selected for the larval starvation test. Larval starvation tests were carried out in the laboratory during the month of February 1994 for Galerucella grisescens and December 1993 for Haltica foveicollis. Fresh leaves of each test plant were placed in a petridish containing wet cotton in a side to maintain suitable humidity. Twenty, first instar larvae were put in the petridish together for test. The test was continued until all larvae had died. The leaves of test plants were replaced as necessary and examined for any evidence of larval feeding. Each test was repeated five times for all test plants. Only helencha Jussiena repens weed plant was selected for Cassida enervis. Two host weed plants were selected for Galerucella grisescens. They were: Biskatali (Polygonum orientale) and Gangpalong (Rumex maritimus). The first instar larvae were transferred individually to each of the hosts and reared in petridishes (90 x 16 mm). The larvae were provided with fresh leaves daily and the petridishes containing wet cotton in a side to maintain suitable humidity. Data on area of food consumption by larvae were recorded daily. The area of the leaves eaten were measured with the help of a transparent graph paper. The test was continued until larval development completed. Each test was repeated ten times for all test plants.

Source of Information: BAU Res. Prog. 9: 160-168, 1995

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Various stages of the life cycle of Cassida enervis and Galerucella grisescens were studied. They are observed to be voracious feeder of the weed helencha, biskatali, gangpalong and nunia.

Knowledge Management: Report/Proceedings