Binomial Sequential Sampling Plans for Cereal Aphids (Homoptera: Aphididae) in Spring Wheat

Abstract

Binomial sequential sampling plans usually are more efficient than sampling plans based on counting the number of insects per sample. Our objective was to develop robust binomial sequential sampling plans based on a range of action thresholds for 3 species of cereal aphids, Rhopalosiphum padi (L), Sitobion avenae (F.), and Schizaphis graminum (Rondani). Aphid population data were collected from 45 eastern North Dakota spring wheat fields during 1993-1995. The proportion of infested stems (P T ) with more than T (tally threshold) aphids was related to mean aphid density (m) with the empirical model ln[-ln(1 - P T )] = a + bln(m). The P T -m relationship fit the data well for T values of 0-4, with T = 3 having the best fit. Binomial sequential sampling plans were developed using a Monte-Carlo computer program based on the empirical model. Tally thresholds were evaluated with operating characteristic and average sample number functions. Increasing the tally threshold from 0 to 3 improved the accuracy of the sampling plans but also increased the average sample number required to make a decision. Sampling stop lines for binomial sequential sampling plans with tally thresholds of and 3 and action thresholds of 9 and 13 aphids per stem, and with a tally threshold of 3 and an action threshold of 17 aphids per stem, are provided for use in spring wheat. Sampling plans should be useful tools for spring wheat growers and crop consultants in the northern Great Plains and be applicable over a range of crop values and management costs.