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Co-operative and Competitive Effect in Country Bean Aphid (aphis Craccivora Koch) at Different Colony Size

Dr. Ranajit Kundu
Ex Professor
Department of Entomology, BSMRAU, Gazipur

Dr. Md. Mohasin Hussain Khan
Professor
PSTU, Patuakhali

M. A. Maleque
Professor
Sylhet Agricultural University

Dr. Mohibul Hasan
PSO (Ex.), BRRI, Gazipur
KGF, BARC. Dhaka

Dr. Sheikh Shamiul Haque
PSO
Entomology Division, BRRI, Gazipur

Abstract/ Executive Summary:

Relative dominance of the two opposed effects of co-operation and competition in colonies of Aphis craccivora Koch was studied on field grown country bean. The relationship between colony size (x) and adult weight (y) of aphids revealed a second order polynominal regression. The area where increasing colony size increased the adult weight of aphid, within which co-operative effect seems to outweigh the competitive one, reached to a peak zone under the colony size of 700-750 aphids. Decreasing adult weight in larger aggregations indicated the dominant effect of competition over co-operation. Increasing colony size increased the production of alatoid nymphs. Reproductive potential (y) was found to show a linear positive relationship with adult weight (x).

Keywords: Aphis craccivora, Colony size, Co-operation, Competition, Alatoid.

Location: Experimental farm, BSMRAU, Gazipur

Start Date: 00-00-1997

End Date: 00-00-1998

Program Area: Pest Management

Commodity: Bean

Objectives:

TO STUDY THE CO-OPERATIVE AND COMPETITIVE EFFECT IN COUNTRY BEAN APHID (APHIS CRACCIVORA KOCH) AT DIFFERENT COLONY SIZE

Methodology:

Country been, Lablab purpureas (variety IPSA 'Seam'-2) was field grown in the experimental farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh, during the crop season, 1997- 98. Standard commercial cultivation procedure was followed except any recourse to aphid control measures. Colony selection and its size determination: Aphid infestation and population build up was allowed to occur naturally. Twenty five colonies of A. craccivora with five from each of the four plant parts viz. inflorescence, twig, pod, and leaf were randomly selected from the plants throughout the field. This was done in the afternoon. After selecting the colonies, all the adult (both apterae and alatae) were removed keeping the record of the removed individuals. Each of the selected plant parts, along with colony inserted inside finely perforated polythene bag, was clipped off from the plant in the following morning and taken to the laboratory. All the individuals in a colony were brushed off on a piece of white paper and counted. Adults removed in the previous afternoon were added to this number to determine the actual colony size in number of aphids per colony. From each colony, five freshly moulted adult apterae were randomly selected and about 25% of the nymphs were preserved in 70% ethyl alcohol for further studies in the laboratory. Weighing, dissection and embryo count: Freshly moulted adult apterae were anaesthetized with chloroform and weighed on an electronic balance and kept separately inside gelatin capsules. These were then dissected on a glass slide using few drops of water under a dissecting microscope. The number of total embryos and welt developed embryos (i.e. with pigmented eye spots) were counted for each of the dissected apterae. Dissection was performed using the standard procedure for aphids as described by Dixon and Dharma (1980a). Determination of percentage alatoid nymph: From the preserved samples of nymphs, the number of apterous and altoid nymphs (having wing pads) were counted and recorded separately for each colony. The percentage alatoid nymphs was calculated relative to total number of apterous and alatoid nymphs.

Statistical analysis: The results were analyzed using single factor ANOVA following completely randomized design. Menus were separated by Tukey's multiple comparison test. Polynominal regression was done for the relationship between colony size and adult weight. Linear regression analyses were performed to explore the relationship between colony size with dispersal parameter and also among adult weight with reproductive potential. The data on percentage alatoid nymph were subjected to angular transformation.

Source of Information: J. Asiat. Soc. Bangladesh, 26(2):189-196, December 20000

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Decreasing adult weight of aphid in larger aggregations indicated the dominant effect of competition over co-operation. Increasing colony size increased the production of alatoid nymphs. Reproductive potential (y) was found to show a linear positive relationship with adult weight (x)

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