SAMPLING METHODS FOR ESTIMATING THE ABUNDANCE AND DISTRIBUTION OF ALL LIFE STAGES OF THE APPLE MAGGOT, RHAGOLETIS POMONELLA (DIPTERA: TEPHRITIDAE)

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Abstract
Sampling techniques for all life stages of the apple maggot, Rhagoletis pomonella (Walsh), were developed and their precision and accuracy evaluated. Reliable estimates were obtained for the egg and larval stages (standard error < 10%), but at the low population levels often encountered in the pupal and adult stages it was necessary to accept a lower level of precision (S.E. ≏ 25%). Eggs and larvae were uniformly distributed within trees. Variation between tree quadrants, and sections at different radii from the trunk, showed that stratification within trees was necessary for reliable estimation of the later stages. Predators acting in a heterogeneous environment under the trees were considered to be the major contributors to this variation. The most consistent source of variation was that between trees.