Abstract
<p>The problem of bark eating caterpillar, <em>Indarbela quadrinotata</em> infestation has been observed from variety of horticulture and forest tree species in India. The estimation of infestation of this caterpillar using conventional sampling methods was found difficult because counting the number of caterpillar in each tree is practically not feasible. Ranked set sampling (RSS) is a cost efficient method which provides improved estimators of mean and variance when actual measurement of the observations is difficult to obtain but a reasonable ranking of the units in the sample is relatively easy. In the present study, poplar, <em>Populus deltoides</em> plantation of Western Uttar Pradesh and Uttarakhand was taken for the assessment of <em>Indarbela quadrinotata</em> infestation. The RSS estimator of population mean and variance have been discussed and compared with the corresponding estimators from simple random sampling (SRS). The relative precision (RP) of RSS procedure with respect to the SRS for four different set sizes of <em>k </em>= 3, 5, 7, and 10 has been deliberated. It was seen that RP increase with the increment in <em>k</em>. The method of RSS was found suitable for the assessment of insect pest infestation.</p><p><strong>Keywords</strong><strong>: </strong><em>Indarbela quadrinotata</em>, <em>Populus deltoides</em>, simple random sampling, ranked set sample, order statistics.</p>
Highlights
The bark eating caterpillar, Indarbela quadrinotata, is economically injurious insect pest
Bark eating caterpillar is a polyphagous and comparatively considered of minor importance in forestry; it is a major pest of Indian gooseberry Emblica officinalis [3, 4]
Female lays egg below the bark or in between cracks and there after larvae bore into the tree continue feeding on the bark for 9 to 11 months, the damage caused by this pest reached maximum during rainy season [1, 6, 7]
Summary
The bark eating caterpillar, Indarbela quadrinotata, is economically injurious insect pest. An effort for the assessment of I. quadrinotata in poplar trees has been made in the present study with the help of ranked set sampling (RSS) which primarily required ranking of trees based on the number of ribbons and their sizes rather than the actual measurement of the number of active insects in each tree. In this method, the first step is to rank the small set of samples of trees by some rough gauging method (say visual inspection) without the actual measurement.
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