Dispersion and Sequential Sampling of Green Cloverworm 1 Eggs in Soybeans 2

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Abstract
The microspatial patterns of green cloverworm eggs were studied within and among soybean plants. The upper leaf surface generally contained significantly more eggs than the lower surface. Few eggs (2.8%) were found on stem or pod surfaces. The distribution of eggs by relative nodal position was influenced by the stage of plant growth. The third node from the terminal was selected as the best relative nodal position from which to sample egg-bearing leaves. Among-plant data were expressed on the basis of three sample-unit sizes. Four dispersion indices were calculated for each data set expressed on the basis of each sample-unit size. The majority of data sets exhibited a random dispersion pattern, although the proportion of data sets categorized as random increased with increasing sample-unit size. Taylor's power function also indicated a random dispersion pattern for all sample-unit sizes. The results of Iwao's regression technique were inconclusive. A two-stage sequential sampling plan is described that estimates egg densities with a predetermined precision level. This plan consists of random samples of leaves, for which variance-to-cost relationships indicated that the optimal number of leaves per sample was four. Cost estimates indicate that this plan is suitable for ecological population studies.

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