Environmental Entomology (1972) 1, 771-780

J. Allen, D. Gonzalez and Aten D.V. Gokhale (1972)
Sequential sampling plans for the bollworm, Heliothis zea
Environmental Entomology 1 (6), 771-780
Abstract: A sequential decision plan based on the sequential probability ratio test has been derived for determining the infestation status of Heliothis zea (Boddie) in cotton. In addition, a sequential counting or estimation plan has also been derived for fixing the coefficient of variation of the mean. Both of these plans are based on 3 years of data from 5 different untreated cotton fields in the San Joaquin Valley of California.
Our general findings based on computer calculations and field trials follow: (1) Five adjacent cotton plants have been found to be a preferable sampling unit to 1- or 3-plant sample units in a sequential decision plan. Although a slight advantage exists in smaller sample units in terms of total plants required, the increased amount of walking between the larger number of small units more than offsets any advantage. (2) If 50 plants per 20 acres are taken as a practical limit on sampling, up to 25% chance of error must be tolerated in a test of 8 vs. 15 worms/ 100 plants. Up to 20% chance of error must be tolerated in a test of 10 vs. 20 worms/ 100 plants. (3) The sequential decision plan agrees well with previous methods (12 5-plant samples) with only one disagreement out of 40 comparisons. In addition, good agreement between predicted and observed sampling requirements was found. (4) Sampling distributions for the cotton bollworm have the characteristic that the sample variance increases more rapidly than the mean. This suggests a clustered spatial pattern and is in wide agreement with the literature. (5) In a sequential counting plan which fixes C, the standard error to mean ratio, very high sampling requirements are indicated at low population means.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)

Research topic(s) for pests/diseases/weeds:
surveys/sampling/distribution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Helicoverpa zea	Cotton (Gossypium)	U.S.A. (SW)