Abstract
The number of hop aphids, Phorodon humuli (Schrank), per main stem leaf at a height of 2 m was representative of aphid density per leaf over the whole hop plant ( Humulus lupulus L.). Therefore, sampling was based on main stem leaves at the 2 m elevation. Taylor’s power law was used to develop a numerical sequential sampling plan for a critical density (control threshold) of aphids. A binomial (presence-absence) sequential sampling plan was developed based on Taylor’s power law. On the average, the binomial method required fewer samples than the numerical method, and the level of error was about as expected. Significantly more aphids were found on border rows of hop yards than in yard interiors. Sampling aphids in hop cones was too time consuming to be practical. Although the number of aphids on leaves was significantly related to the number in cones, determining numbers in cones from leaf samples was too inaccurate for management purposes.
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