The Use of Wald’s Sequential Probability Ratio Test (SPRT) in Cocoa Pod Borer Management
DOI:
https://doi.org/10.11113/jt.v63.1904Keywords:
Cocoa pod borer, cocoa, sequential sampling plan, Wald’s SPRTAbstract
Sequential sampling plan (SSP) has been widely used in many engineering and quality control study. The advantage of using the SSP is the sample size is not fixed in advance, but is determined in part by the results of the sampling process. The application of the SSP is not limited to the industry, it also being used in pest management. This is because the SSP are generally more cost effective than plans based on a fixed sample size. Wald's Sequential Probability Ratio Test (SPRT) is one of the most common sequential sampling plans in insect pest management. It has been used to determine pest status at one time which could be used, through time, to monitor the status of the population and to take action when the pest density exceeded the Economic Threshold Level (ETL). Cocoa pod borer or CPB (Conopomorpha cramerella (Snell)) is a pest of concern to the cocoa growers in South-East Asia that has become one of the major factors that dampened the interest expressed in cocoa cultivation because of the heavy losses of cocoa pods due to the pest if effective control measure is not employed. The chemical control appeared to be one of the effective control measure used by the growers to control the CPB. Current practice used by the growers in applying the chemical is biweekly spraying which could see the increasing cost of chemical and labor used. The study was conducted to develop the Wald’s SPRT to monitor the CPB infestation level relative to the ETL based on counting the CPB eggs found on the pods aged 1 month before ripen or pod length 131 mm to 150 mm. The performance of the Wald’s SPRT was validated using independent data sets collected from Cocoa Research and Development Center (CRDC) Madai.
References
Waters, W. E. 1955. Sequential Sampling in Forest Insect Surveys. Forest Science. 1: 68–79.
Fowler, G. W. and Lynch, A. M. 1987. Sampling Plansi Insect Pest Management Based on Wald’s Sequential Probability Ratio Test. J. Environ. Ento. 16: 345–354.
Carter, J. L. F. W. Ravlin, D. R. Gray, R. Carter, and C. W. Coakley. 1994. Foliage Presence and Absence Effect on Gypsy Moth (Lepidoptera: Lymantriidae) Egg Mass Sample Counts and the Probability of Exceeding Action Thresholds With Foliage Present. J. Eco. Ento. 87: 1004–1007.
Lye, B. & R. N. Story. 1989. Spatial Dispersion and Sequential Sampling Plan of the Southern Green Stink Bug (Hemiptera: Pentatomidae) on Fresh Market Tomatoes. J. Environ. Ento. 18: 139–J44.
Azhar, I. 1986b. Ancaman Pengorek Buah Koko (Conopomorpha Cramerella) Terhadap Industry Koko di Malaysia. III. Pengurusan Perosak Bersepadu dan Langkah-Langkah Awal Pencegahan Serangan Perosak Ini. Teknol. Koko-Kelapa. MARDI. 2: 71–76.
Azhar, I. and Long, G. E. 1991. The Ecology of Cocoa Pod Borer. Conopomorpha cramerella (Snellen) (Lepidoptera: Gracillariidae). In Malaysia: Dispersion Pattern and Sampling Plan for Eggs on Pods. J. Trop. Plant Prot. 8: 98–102.
Albert, L. and Azhar, I. 2010. Determination of the Economic Injury Level of Cocoa Pod Borer. Malaysian Cocoa J. 6: 13–18.
Sokal, R. R. and Rohlf, F. J. 1995. Biometry: The Principles and Practice of Statistics in Biological Research. 3rd ed. W.H. Freeman, New York.
Davis, P. M. 1994. Statistics for Describing Populations. Pages 33-54 in: Handbook for Sampling Methods for Arthropods in Agriculture. L. P. Pedigo and G. D. Buntin, eds. CRC Press, Boca Raton, FL.
Southwood, T. R. E. 1978. Ecological Methods with Particular Reference to the Study of Insect Populations. 2nd Edition. Chapman and Hall. London, UK.
Oakland, G. B. 1950. An Application of Sequential Sampling to Whitefish Sampling. Biometrics. 6: 59–67.
Bliss, C. I. and Owen, A. R. G. 1958. Negative Binomial Distributions with a Common k. Biometrika. 45: 37–58.
Downloads
Published
Issue
Section
License
Copyright of articles that appear in Jurnal Teknologi belongs exclusively to Penerbit Universiti Teknologi Malaysia (Penerbit UTM Press). This copyright covers the rights to reproduce the article, including reprints, electronic reproductions, or any other reproductions of similar nature.
