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Effect of Temperature, Rainfall and Relative Humidity on Seasonal Incidence of Major Rice Insect Pests

Md. Niaz Morshed
Bangladesh Rice Research Institute (BRRI), Adaptive Research Division, Gazipur-1701, Bangladesh

Md. Eftekhar Uddin
Bangladesh Rice Research Institute (BRRI), Rice Farming System Division, Gazipur-1701, Bangladesh

Md Hasibur Rahaman Hera
Bangladesh Rice Research Institute (BRRI), Plant Pathology Division, Gazipur-1701, Bangladesh

Naznin Sultana
Department of Agriculture extension (DAE), Dhaka-1215, Bangladesh

Abstract/ Executive Summary:

An experiment was carried out under field conditions at the Bangladesh Rice Research Institute, Regional station Sonagazi, Feni, to determine the effect of abiotic factors on the seasonal incidence of major rice insect population at the south-east coastal region of Bangladesh during T. Aman, 2019. Insects were collected from the experimental plot by using the sweep net method and weather data was recorded simultaneously from the meteorological observatory. The highest percent of dead hearts (10.51) and white heads (9.38) occurred during the 2^nd week of October and the 1^st week of November, respectively. The correlation studies with abiotic factors revealed that temperature and rainfall showed a negatively significant impact on the population of S. incertulas (white heads) but rainfall showed a positive non-significant impact on the dead heart. Temperature and relative humidity both showed a negatively non-significant impact on dead hearts and white heads respectively but relative humidity showed a positive significant impact on dead hearts. Leaf folder infestation attained its peak during the 2^nd fortnight of October and didn't get significantly affected by rainfall, relative humidity and temperature. Green leaf hopper attained peak population during October-November. GLH showed a negatively significant correlation with minimum temperature, while it was not significantly affected by other weather parameters viz, maximum and average temperature, rainfall and relative humidity. Rice bugs have a negative non-significant effect with relative humidity and temperature but a negatively significant effect with rainfall. These findings will be helpful for proper and timely management of the major rice insect pests in the south-east coastal region of Bangladesh.

Keywords: Insect, Pest, Abiotic factors, Rice yellow stem borer, Rice leaf folder, Rice bug, Green leaf hopper

Location: Bangladesh Rice Research Institute (BRRI), Regional Station, Sonagazi, Feni, Bangladesh.

Start Date: 00-00-2019

End Date: 00-00-2019

Program Area: Pest Management

Commodity: Insects, Rice

Objectives:

To study the effect of abiotic factors on the population build-up of major rice insect pests.

Methodology:

The experiment was conducted during the Kharif-2 (T. Aman), 2019 season at the Bangladesh Rice Research Institute (BRRI), Regional Station, Sonagazi, Feni, Bangladesh. The experimental plot was located at 22.88° North (latitude) and 91.43° East (longitude) at an average elevation of 11m above from the sea level belonging to the Chittagong Coastal plain (i.e., Agro-Ecological Zone-18). The mean maximum temperature experienced during the experiment was 35.36°C during the 3^rd week of September and the mean minimum temperature was 22.07°C during the 1^st week of November. The maximum rainfall experienced was 16.57mm during the 3^rd week of September. The seasonal incidence of insect pests on rice was studied on a separate plot of 33 decimal (1 bigha). The nursery was raised adjacent to the main experiment plot to study the population build-up of the pests. BRRI dhan71 rice variety was used as an experimental crop for this study. It is one of the most popular T. Aman high yielding rice varieties in Bangladesh having 110-115 days growth duration and grown in irrigated and medium upland condition having a special feature of good grain quality. Thirty days old seedlings were transplanted to the main field with a spacing of 20×15 cm² in hills (2 seedlings/hill) and all the agronomical practices viz. irrigation, fertilizer application and intercultural operations were followed as recommended for rice crop in this area to raise the crop. No chemical pesticides were applied throughout the crop period to get a natural pest incidence on the crop. A sweep net with 40 cm in diameter equipped with a 150 cm long handle was used to collect insect in the rice field in the daytime following the method by Nasirudin and Roy, 2012. The sweep net was swung about 180° arc such that the net rim strikes the top 6 to 8 inches of paddy growth. Each 180° arc was counted as one sweep (Hashim et al., 2017). Each sample represents twenty complete sweeps of sweep net from the experimental plot. Five samples were taken for each sampling day. The pest population was recorded in this unprotected plot at 7 days interval from the occurrence or initiation of pest infestation and was continued up to maturity. The incidence of pests was recorded on 10 randomly selected hills, in the case of each insect. Weather data was also recorded simultaneously from the meteorological observatory available at the Bangladesh Rice Research Institute (BRRI), Regional Station, Sonagazi, Feni, Bangladesh and correlated with the percent incidence of the pest population. The correlation coefficient method was adopted to work out the relationship between the occurrence of the pest incidence and the weather parameters. The infestation of yellow stem borer was observed in two phases, one at vegetative phase as percent dead hearts and the second at a reproductive phase as percent white heads from 10 randomly selected hills. Population counts were taken on the number of dead hearts/white heads and a total number of tillers/ panicle from 10 randomly selected hills (Justin et al., 2013). For the observations of Green leaf Hopper (Nephotettix nigropictus), Rice yellow Stem borer (Scirpophaga incertulas) and Rice bug (Leptocorisa acuta) the population was recorded by sweeping insect collecting nets five times across each treatment and the numbers of nymphs and adults were counted (Rai et al., 1990). Weekly data of pest population were correlated with the prevailing climatic factors such as maximum temperature, minimum temperature, morning and evening relative humidity prevailing in the field. The correlation coefficient (r) analysis was carried out by using IBM SPSS Statistics 20.

Source of Information: International Journal of Biosciences; Vol. 17, No. 6, p. 92-102, 2020

Article Link (Online Journal): http://dx.doi.org/10.12692/ijb/17.6.92-102

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

From the above findings, it may conclude that the peak period of S. incertulas population (10.51%) were recorded in 2^nd week of October (42^nd standard week) at vegetative stage (Dead hearts) and in 1^st week of November (45^th standard week) during reproductive stage (White ears). The above research revealed that the incidence of yellow stem borer or the percent dead hearts were observed highest during the vegetative phase and percent white ears were highest during the reproductive phase of the plant. So, if it is controlled at an early stage it will not have a loss in the reproductive phase. The correlation studies with abiotic factors revealed that temperature and rainfall showed a negatively significant impact on the population of S. incertulas (white heads) but rainfall showed a positive non-significant impact on the dead heart. Temperature and relative humidity both showed a negatively non-significant impact on dead hearts and white heads respectively but relative humidity showed a positive significant impact on dead hearts. The leaf folder population didn't get significantly affected by rainfall, relative humidity and temperature, so it is better to take preventive measures from the start of September month. Green leaf hopper attained peak population during October- November. GLH showed a negatively significant

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