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Abundance and Diversity of Beneficial Insect and Spider Species on Rice Ecosystem in Sylhet Region

M Rahman
Department of Entomology, Faculty of Agriculture, Sylhet Agricultural University, Sylhet-3100, Bangladesh

M A Maleque*
Department of Entomology, Faculty of Agriculture, Sylhet Agricultural University, Sylhet-3100, Bangladesh

M S Uddin
Department of Agroforestry and Environmental Science, Faculty of Agriculture, Sylhet Agricultural University, Sylhet-3100, Bangladesh

J Ahmed
Department of Entomology, Faculty of Agriculture, Sylhet Agricultural University, Sylhet-3100, Bangladesh

Abstract/ Executive Summary:

An attempt was made to determine the abundance and diversity of beneficial insect and spider species on Boro rice during the period of November 2013 to April 2014 and Aman rice during May to November 2014 at Agricultural Training Institute (ATI) farm in Sylhet district. A considerable number of beneficial insect and spider species namely ladybird beetle, carabid beetle, ground beetle, damselfly, mirid bug, ant, wasp, dipteran fly, lynx spider, wolf spider, jumping spider and long-jawed spider were found abundant at all growing stages in both rice fields. The relative abundance of insect and spider species in Boro rice ranked as ladybird beetle>damselfly>ant>wolf spider>jumping spider>ground beetle>wasp>tachinid fly>lynx spider>carabid beetle>mirid bug; whereas in Aman rice it was ranked as ladybird beetle>damselfly>long-jawed spider>dipteran fly>jumping spider>lynx spider>ant>wasp>carabid beetle. Araneae order showed the highest values while Coleoptera order showed the lowest values for Diversity index and evenness in both Boro and Aman rice. Richness index was found highest in Araneae order in Boro rice and lowest in Coleoptera order in Aman rice fields. The results clearly indicate that rice ecosystem could be utilized as a great reservoir of beneficial insect and mite species and thus rice ecosystem would foster natural biological control process in rice based agro-ecosystems all over Bangladesh especially in the Sylhet region.

Keywords: Beneficial insect, Rice ecosystem, Biodiversity, Rice season.

Location: Agricultural Training Institute (ATI) farm in Sylhet district.

Start Date: 00-11-2013

End Date: 00-11-2014

Program Area: Pest Management

Commodity: Insects, Spider, Rice

Objectives:

The present study was conducted to generate new information about the prevailing abundance and diversity of beneficial insect and spider species in Aman and Boro rice field in Sylhet region.

Methodology:

The experiment was conducted to determine the abundance and diversity of beneficial insect and spider species in Boro and Aman rice fields of Agricultural Training Institute (ATI) farm during November 2013 to April 2014 (Boro rice) and May to November 2014 (Aman rice). The experimental plot was located at 24.56°N latitude and 91.8° E longitudes at an average elevation of 19 m above the sea level belonging to the Eastern Surma-Kushiyara Flood Plain (i.e., Agro-Ecological Zone-20).Sampling and identification of beneficial insect and spider Sampling of beneficial insect and spider was done at three stages of rice growth, i.e. seedling, tillering and heading. The beneficial insect and spider were collected with a fine nylon cloth sweep net (30 cm dia.) from both Boro and Aman rice plots. Sweeping was done from the plant canopy level including inter spaces between plants as well as close to basal region of the plants as far as possible. In each rice fields, 20 complete sweeps were made randomly to collect the beneficial insect and spider species for each sample and sampling was done with three replications each in all stages. Sampling was done early morning (9.00 to 11.00 am) in both rice fields. The beneficial insect and spider species of each sample were separated and preserved in a labeled container with 70% alcohol. Afterwards, the collected samples were carefully counted and identified to order and family and common names with the help of taxonomic keys in given different publications (Borroret al., 1963; Richards and Davies, 1977; Heinrichs, 1994). Species richness of beneficial insect and spider To provide a cohesive overview of species richness, Margalef's Index was calculated along with S (actual number of species collected). Margalef's index (Margalef, 1958; Khan, 2013) assumes a theoretical relationship between the number of individuals (N) and the number of species (S) of that taxonomic group observed in a sample and is expressed as follows: M.I. = S−1/logN

The index logarithmically scales the value of S, and hence provides a means of comparison between stations with different ratios of S andN.Relative abundance of beneficial insect and spider The relative abundance of beneficial insects was calculated using the following formula:

Relative abundance (%) = Total no. of individuals of each species/Total no.of individuals of all species x100

Analysis of data The data were analyzed using MSTAT-C Computer Software (Russel, 1986). The analysis of variance (ANOVA) was calculated for interpretation of abundance of natural enemies at different growth stages of Boro and Aman rice. The means were separated and compared using Least Significant Difference (LSD) test.

Source of Information: J. Sylhet Agril. Univ. 4(1):63-70, 2017 ISSN: 2308-1597

Article Link (Online Journal): www.jsau.com.bd

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Major pest species of rice plants need to be controlled in the field using environmentally safe methods of pest management as alternative to toxic chemical pesticides. The main pest control method of rice crops in Bangladesh is still the application of chemical pesticides on the infested fields. Alternative pest management method(s) viz., use of resistant varieties, reduced use of insecticides, and conservation of bio-control agents need to be developed for rice pests. The judicious use of insecticides in rice crops greatly contribute to restoring various ecosystem functions like predation, parasitism, pollination, etc. and to minimizing human health hazards and environmental pollution. The present results clearly indicate that the diversity indices of beneficial insect and spider species were highest in the order Araneae compared to the order Coleoptera in Boro and Aman rice plots. Diversity indices of other orders were zero due to the presence of single species which indicates that there is no diversity of species under those orders. It is true that population of predatory insects such as ladybird beetle, spider and damsel fly are more abundant in rice fields, suggesting that rice ecosystems could be used as large reservoir of predatory insect and mite species and thus could be used to enhance natural biological control process of insect pest and mite species in rice based agro-ecosystem in Bangladesh particularly in the Sylhet region.

Knowledge Management: Journal