SEQUENTIAL SAMPLING FOR ADULT COCCINELLIDS IN WHEAT

Adult aphidophagous coccinellids are important predators of cereal aph ids in wheat in the Great Plains of the United States for which sampli ng methods are needed to facilitate improved management. An equation r elating the mean number of adult coccinellids per m(2) in a wheat fiel d to its variance was obtained using Taylor's power law. A sequential sampling procedure was developed to estimate the number of adult cocci nellids per m(2) with constant average statistical precision (standard error/mean). The procedure was constructed by an equation relating th e number of adult coccinellids per m(2) to the number of adult coccine llids per minute of counting incorporating into the Taylor's power law relationship. The procedure involves conducting a series of 1-min cou nts while walking through a field at a constant velocity of 10 m per m inute. After each 1-min count sequential sampling stop-lines are consu lted to determine if the specified level of precision has been achieve d. Two methods, a statistical procedure and comparison with independen t data, were used to assess the consistency with which the specified l evel of precision was achieved by the procedure. Results indicated tha t observed precision was close to that specified by the user over a wi de range of adult coccinellid density.