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Study on the Relative Abundance of Insect Pests and Their Natural Enemies Associated in Rice

M. M. Rahman
Assistant Professor
Department of Entomology, Sher-e-Bangla Agricultural University, Dhaka-1207

Abstract/ Executive Summary:

The field experiment was conducted at Bangladesh Agricultural University (BAU) farm in Mymensingh during Boro season. Thirteen different rice pests viz. Short- homed grasshopper, yellow stem borer, dark- headed striped borer, pink borer, white- backed plant hopper, green leafhopper, brown plant hopper, zigzag leafhopper, whorl maggot, long homed grasshopper, rice leaf roller, green semi looper and rice bug were recorded during the present study. Among the stem borers, yellow stem borer (Scripophaga incertulas) was most dominant throughout the crop season followed by the dark- headed striped borer (chilo polychrysa) and pink borer (Sesamia inferens). Green leafhopper (Nephotettix virescens) was the dominant species among the plant- sucking insects. The population of leaf feeding insects was quite high and their densities varied in relation to plant age and season. Local improved Pajam had lower infestation than high yielding variety BR2. Twelve natural enemies (predator/ parasitiod) were recorded from the crop field. They were carabid beetle (Ophionea nigrofaciata), damselfly (Agriocnemis famina), ladybird beetle (Micraspis discolor, M. crucea, Menochilous sexmaculatus), spider (Tetragnathus sp. Oxyopes sp. and Lycosa pseudoanmulata), mirid bug (Cyrtorhinus lividipennisi), Tetrastichus schoenobii and Telenomus rowani. The ladybird beetle Micraspis discolor was abundant from early to late stage of rice crops.

Keywords: Rice pests, Natural enemies, Boro rice

Location: Bangladesh Agricultural University farm, Mymensingh

Start Date: 01-01-2005

End Date: 31-12-2005

Program Area: Pest Management

Commodity: Rice

Objectives:

1. To find out the varietals performances of local improved Pajam and high yielding rice variety BR2 in reducing pest infestation and supporting abundance of natural enemies, 2. To find out the seasonal pattern of pests and its damage effects on the growth phases of rice.

Methodology:

The field experiment was conducted at Bangladesh Agricultural University farm in Mymensingh during Boro season. The soil of the study area was under Brahmmaputra alluvial tract with sandy loam soil texture. The climate was characterized by high rainfall and high temperature during the kharif season. The experiment was conducted with the rice variety Pajam and BR2. The factorial experiment was laid out in a 72 m² plot demarcated into six equal blocks and 3 m x 4 m with 0.5 m gap between main plots and blocks, and 2 m spaces in borders on all sides. At first land was ploughed with a rotavator and then with a country plough followed by laddering. Experiment plots were fertilized with nitrogen, phosphate and potash at the rate of 80- 60- 40 kg/ ha. Urea, Triple super phosphate (TSP) and Murate of potash (MP) were used as sources of N. P. K. respectively. The entire amounts of TSP, MP and 1/3^rd of urea were applied at the time of final land preparation. The rest amount of urea was top dressed in two equal splits at maximum tillering and before panicle initiation stage. The seedling age for transplanted variety was 25 days. Two seedlings were transplanted in each hill and water levels in the study plots were maintained at 8-10 cm for about 7 days with alternate drying and irrigation for another 15 days. During vegetative and reproductive phase irrigation were applied. No pesticide was used in the experimental fields. The major pests of rice and their natural enemies (Predators and parasitoids) were collected by a sweep net (diameter 30 cm) from the top portion of the plants as well as close to the basal region of the plants. Usually ten sweeps were made to collect the adult, nymphs and larvae of insect pests and predators. The sweeping was started from 20 days after transplantation (DAT) and continued weekly up to milking stage of rice plants. Collected insects were killed in killing jar provided with cotton (ball) soaked with chloroform. Then the soft bodied insect pests and predators were preserved in 80% alcohol and identified in the departmental laboratory using available keys. Intercultural operations required as per recommendation for rice cultivation. Ten random sweeps per plot were made to collect the rice green leafhopper and its predators. The sweeping started from 20 days after transplantation (DAT) and continued up to 77 DAT, with 7 days interval. Samples were taken to the laboratory for counting and identifications. The statistical packages used for the analysis were M stat and path analysis programme. The analysis of variance (ANOVA) of the results on various insect pests abundance and prey- predator association were done on the square root transformed values. Their mean were separated by Duncan's' Multiple Range Test (DMRT) on insect pest attack and their natural enemies associated with indigenous rice variety, Pajam and HYV BR2 separately but both in T. Aman season.

Source of Information: JOURNAL OF SHER-E-BANGLA AGRICULTURAL UNIVERSITY, Vol. 01 (1), July 2007, pp. 09-15.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It may be concluded from the study that among the borer Scirpophaga incertulas occur abundantly followed by Chilo polychrysa with medium intensity and Sesamia inferens have low level of intensity. All the sap sucker viz. White-2 backed plant hopper (WBPH), Green leaf hopper (GLH) and Brown plant hopper (BPH) had high level of intensity except Recilia dorsalis with medium level of intensity of attack. Among the listed leaf feeder 50% of them had high level of intensity of attack. Two recorded parasitoids, Telenomus rowani and Tetragnatha schoenobii occurred with high intensity. Incidence of predators like spiders and lady bird beetles appeared with high to low intensity. Numerically higher infestation of insect pests and their natural enemies recorded in HYV of rice (BR2) compared to those of indigenous rice variety Pajam.

Knowledge Management: Journal