Citation
Idris, Dauda
(2023)
Estimation of microclimate parameters on infestation rate of yellow stem borer (Scirpophaga incertulas) on MR297 rice variety.
Masters thesis, Universiti Putra Malaysia.
Abstract
Scirpophaga incertulas is a predominant insect pest in rice cultivation that causes
significant yield losses and is responsible for severe infestation exhibiting dead heart and
white ear symptoms at vegetative and reproductive stages. Rice is the second highestyielding
grain and a staple diet in most countries. In Malaysia, rice is a vital plant, with
an average daily consumption of 2.5 plates per head, and about 10% to 33% of the yield
losses in the granary area of Malaysia during rice production are due to S. incertulas.
However, information on the estimation of microclimate parameters in Malaysia on the
infestation rate of yellow stem borer on MR297 rice variety is still not studied. The use
of Artificial Neuron Network (ANN) and Multi-Linear Regression (MLR) in forecasting
pest infestation and development has been used. However, this was not the case for
yellow stem borer. Therefore, a series of experiments were conducted to obtain a study
on the yellow stem borer. Adult yellow stem borers were collected using a Malaise trap
from the Integrated Agricultural Development Area (IADA) Laut Barat Selangor. They
released into a cage with 21-day-old paddy to allow them to copulate to achieve the
following specific objective of the study.
The first study objective was to investigate the in-vitro culture and developmental
changes of S. incertulas under different microclimate conditions in the Laboratory
(27.26ºC + 0.92 and RH of 67.43% + 1.3) and shade house (33.16ºC + 0.87 and RH
84.30% + 1.43). Based on the findings, culturing of S. incertulas under laboratory and
shade house conditions assumes significance in addressing the developmental growth
of S. incertulas via identifying the lengths and widths as essential parameters for
appropriate identification of the larval and pupal stages. The development time taken by
the S. incertulas increases as insects develop faster, leading to early population growth.
The correlation analysis of the data showed a significant relationship between the length
and width of the fourth and fifth instar development in the Laboratory correlated to the
minimum and maximum relative humidity. In contrast, pupae length and width in the
field were significantly related to the minimum relative humidity and maximum
temperature.
For the second aimed to determine the infestation and damage of S. incertulas on rice
under different microclimatic conditions in Shade House (33.16ºC + 0.87 and RH of
84.30% + 1.43) and glass house (25.20ºC + 0.29 and RH of 74.50% + 2.12). The dead
hearts at the vegetative phase revealed a significant mean percentage of infestation rate
at 10 Days after treatments (DATS) to 40DATS ranging from 10.00% to 71.25% in the
glass house, slightly higher than in the shade house 6.25% to 70.63%. Also, at the
reproductive stage, the glass house had the highest infestation rate of white ears, which
varied from 5.00% to 58.75%, in contrast to the shade house, which had a mean
percentage of 5.00% to 31.88% during the 40DATS to 70DATS under different
microclimate conditions. Therefore, microclimates like temperature and relative
humidity significantly affect the infestation rate of the S. incertulas on rice.
The final study aimed to estimate the yellow stem borer infestation rate with abiotic
factor using an artificial neuron network (ANN) and Multi-linear regression model,
which effectively estimate the best model and their comparison on performance. The
Lavenberg-Marquardt algorithm was used to train the input and target. The slightly large
dispensary between ANN's training, validation, and testing performance over MLR
suggests that ANN revealed significant positive coefficients of determination between
the microclimate and infestation rate of S. incertulas. The results showed a strong
coefficient of determination between the S. incertulas infestation rate with the morning
minimum and maximum temperature in a shade house compared to the glass house,
where the infestation rate of S. incertulas was positively correlated to the afternoon
minimum and maximum relative humidity.
In conclusion, the estimation of microclimate parameters on the infestation rate of yellow
stem borer on MR297 rice variety in Malaysia to estimate the infestation rate with abiotic
factors was the first of its kind for modeling and forecasting the infestation rate of S.
incertulas. The present study's finding recommends that rice farmers and entomologists
develop a pest management program for yellow stem borer and stimulate research
workers for sustainable bio-resource management. Further studies are required for proof
of concept in the field experiment to ascertain the infestation rate of S. incertulas using
forecasting of imaging processing and prediction with abiotic factors.
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