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Relative Abundance of Insect Pests and Loss Assessment of Rice Seeds at Different Storage Conditions

M.T.H. Howlader
Department of Entomology, Bangladesh Agricultural University, Mymensingh-2202

M.A. Hague
Department of Entomology, Bangladesh Agricultural University, Mymensingh-2202

M. Shahjahan
Department of Entomology, Bangladesh Agricultural University, Mymensingh-2202

Abstract/ Executive Summary:

An investigation on the abundance of storage insects of rice seeds and loss assessment was made In Aman during February to July, 2002 and Boro during May to October, 2002 in different storage structures viz. Dole, Motka, Kolshi, Steel Drum, Kerosene Tin, Polythene/Plastic Bag, Gunny Bag and Plastic Drum at three villages of Mymensingh Sadar Upazila. Analysis of seed sample of 250g from each storage structure at monthly interval showed four insect species namely, Sitotroga cerealella Oliv., Rhizopertha dominica Fab., Sitophilus oryzae L. and Tribolium castaneum Hebst. A higher insect population was recorded in Boro seeds. In Aman, the mean number of S. cerealella, R. domonica, S. oryzae, T. castaneum was recorded as 13.8, 2.1, 0.38, 0.6, respectively and in Boro, it was 18.6, 1.6, 2.7, 1.0 in 250g of seeds, respectively. The highest insect population, seed damage and weight loss were recorded in Gunny Bag and the lowest were in metal structures (Steel Drum in Aman or Kerosene Tin in Boro) followed by Polythene/Plastic Bag. Seed damage and weight loss were increased with the storage period in Aman but decreased after an initial increase in Boro. The highest moisture content was also found in Gunny Bag. More than 80% germination was recorded in all structures except in Gunny Bag in both seasons after six months. The germination was decreased with an increasing storage period. Therefore, the storage structures, Steel Drum, Kerosene Tin and Polythene/Plastic Bag could be used for the safe storage of rice seeds.

Keywords: Storage structures, Storage period, Storage insects, Abundance, Seed quality

Location: Three villages namely, Boyra, Chatrapur, and Sutiakhali of Mymensingh Sadar Upazila and in MS Laboratory of the Department of Entomology, Bangladesh Agricultural University, Mymensingh-2202

Start Date: 00-01-2002

End Date: 00-10-2002

Program Area: Postharvest and Agro-processing

Commodity: Insects, Rice

Objectives:

The situation is quite vulnerable in Bangladesh because of (i) hot and humid climate favouring rapid insect population development, deterioration of seed storage life and (ii) the lack of knowledge and facilities to prevent such losses. Insects were reported to be the number one factor causing 10 percent losses in storage (Islam, 1984). The present study was undertaken to investigate the impact of storage structures on insect infestation in rice.

Methodology:

The present study was conducted in three villages namely, Boyra, Chatrapur, and Sutiakhali of Mymensingh Sadar upazila and in MS Laboratory of the Department of Entomology, Bangladesh Agricultural University, Mymensingh-2202 during January to October, 2002. Identification of the rice seed storage structures To identify the storage structures used by the farmer's for storing rice seeds, data were collected by farm survey with a pre-made questionnaire during January to February 2002. A total of 169 farmers were randomly interviewed. The prevalence of insect pests of stored rice seeds at various traditional storage structures was studied in Aman and Boro season.

Prevalence of insect pests and determination of their population Seed samples of 250g were collected by a Trier from the top layer of farmer's storage structures (15-20 cm). Samples were kept in a polythene bag with an identification card and tied with a thread. Samples were collected from each storage structure at monthly intervals for six months of each season (For Aman during February to July 2002 and for Boro during, May to October 2002) and were brought to MS Laboratory of the Department of Entomology, Bangladesh Agricultural University, Mymensingh. Thirty-six farmers and eighteen farmers were selected for Aman and Boro season, respectively. Seeds of BR-11 and BR-14 rice varieties were selected for Aman and Boro season, respectively. For easy identification and counting, samples were kept in deep freeze (2-4°C) for a few minutes and then a total number of insects of each insect species was counted for each sample. Different prevailing insects were identified based on their respective identifying characters.

Assessment of seed quality The quality of rice seeds was assessed by determining percent seed damage, weight loss, moisture content and germination percentage. Seed damage: The seed damage caused by insects sample was determined at monthly intervals and expressed as percent seed damage with the following formula:

Seed moisture content: Moisture content of samples was measured every time after collection by electric moisture meter (Grain Moisture meter, Riceter J, by Kett Electric Laboratory, Japan).

Germination percent: The viability of seeds was determined by petridish method using filter paper as medium. For these, 400 seeds were selected and placed in petridish and wet by applying water. These were kept in the laboratory having the temperature 25±2-⁰C. Germination was recorded after 10 days of seed set. The percentage of all the seeds was calculated for each seed sample and then the average was obtained for all replications (ISTA, 1985).

Statistical Analysis Completely Randomized Design (CRD) was used to analyze the data. The recorded data on various parameters were statistically analyzed after the necessary transformation using MSTAT statistical package programme. Analysis of variance (ANOVA) and Duncan's Multiple Range Test (DMRT) was done as follows by Gomez and Gomez (1984).

Source of Information: J. Bangladesh Agril. Univ. 2(2): 271-279, 2004 ISSN 1810-3030

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

On average, 2.50 % and 2.65 % seed damage was found after six months of storage at the Aman and Boro season, respectively. This result was in the range. as earlier reported by Mookherjee et al (1998). The result of weight loss also coincided with the findings of Thakur and Sharma (1996). Mandal et aL (1984) and Irshad and Talpur (1993) also made similar observations. Germination of rice seeds gradually decreased with the advancement of the storage period. This trend was also reported by Kaur et al (1990). After sb.< month, all structures except Gunny Bag showed more than 80% germination. Seeds in Gunny Bag have produced the lowest germination. This might be due to the insect infestation, as they feed seed kernels and reduce viability. Khare et al (1974), Mian and Fakir (1989), Ahmed (1990), and Eswarappa et al (1991) also reported similar results. Seeds stored in metal storage structures like Steel Drum, Kerosene Tin produced higher germination, as supported by Khare et al (1974) and Hague (1982). Thus, metal structures seem to be better than other structures as mentioned by Rabbani (1976) and Rao (1978). Therefore, Gunny Bag should be avoided for rice seed storage purposes and metal structures like Steel Drum, Kerosene Tin and also Polythene/ Plastic Bag can be considered for safe storage of rice seeds

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