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Effect of Some Climatic Factors on Helopeltis Infestation of Tea

Mainuddin Ahmed
Bangladesh Tea Research Institute

Md. Jasim Uddin
Bangladesh Tea Research Institute

Abstract/ Executive Summary:

An experiment was conducted on the effect of some climatic factors on the Helopeltis infestation of tea at BEF of BTRI, Srimangal during 1998-2002. Monthly data on the infestation were collected from 50 clonal tea plants of Bilascherra Experimental Farm with systematic sampling method. Five years meteorological data were also collected for the study. Climatic factors- cloud coverage, temperature, relative humidity and rainfall have showed positive relationship with Helopeltis infestation on tea. All the four parameters were found highly correlated (r=0.99, 0.92, 0.81 & 0.95 respectively) with the infestation. Wind speed was also found to be positively correlated with Helopeltis infestation (r=0.78). On the other hand, sunshine hours and water requirement of crop were found to be negatively correlated (r=0.91 & r=-0.46) with the insect. All correlation coefficients are statistically significant at 5% level of significance except in the case of the water requirement of the crop. The findings may be helpful in rescheduling the insecticides use and modifications of some available control options to minimize the infestation.

Keywords: Climatic, Infestation, Tea, Meteorological

Location: Meteorological Department, Dhaka.

Start Date: 00-00-1998

End Date: 00-00-2002

Program Area: Pest Management

Commodity: Insects, Tea

Objectives:

To determined effect of some climatic factors on helopeltis infestation of tea.

Methodology:

The meteorological data of maximum and minimum temperature, sunshine hours, rainfall and wind speed of the experimental area were collected from the Meteorological Department, Dhaka. Pest infestation was collected during the period (1998-2002), systematic sampling method was followed from the Bilascherra experimental farm of Bangladesh Tea Research Institute (BTRI).Tea plantation in an area of 0.016 ha having fifty clonal tea plants was surveyed at monthly interval throughout the year. All pluck able shoots per bush were plucked and weighed during the day of plucking. Helopeltis infested shoots, their number and yield were recorded. The percentage of infestation per plant was calculated by Lubischev's analytical method. The monthly percentage of infestations was compared with the weather parameters, such as cloud coverage, temperature, relative humidity, sunshine hours, rainfall, wind speed and water requirement of the crop and correlation analysis was done between these parameters and Helopeltis infestation. Mean monthly values were computed from seven years of meteorological data (1994-2000). For the computation of mean temperature, average value of maximum and minimum temperature was taken.

Source of Information: Tea j. of Bangladesh, 37(1&2); 2007

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It is evident from the present study that cloud coverage has direct and great positive impact on Helopeltis infestation on tea during the production period (May- September). The correlation co-efficient is statistically significant (r = 0.99). On the other hand, sunshine regime had negative relationship (r = 0.91) with infestation rate as was observed through May- September, whereas the infestation was found lower for the remaining months because of higher values of mean monthly sunshine hours. Temperature and relative humidity are normally high during the period April- September for which infestation was observed higher than the other months. The data also reflect that regular as well as lower rainfall has positive correlation with Helopeltis Maximum rainfall in May-July showed less infestation. It was also found that water requirement of crop played negative role(statistically insignificant) on Helopeltis infestation during the production period of tea (April - September). Wind speed was found favourable for infestation that is the higher mean monthly values of wind speed, the higher the infestation percentage and vise-versa. The correlation co-efficient is significant at 5% level of significance. Although the climatic factors are beyond control in nature, some of the this situations interfere with the spray fluids and also might have influenced resistance or tolerance of the pest due to exposer to inadequate toxicity from the applied chemical. Thus knowing the behaviour of this particular pest under variable climatic factors, this study may be helpful in rescheduling the insecticide use and modifications of some available control options to minimise Helopeltis infestation.

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