4.4.1. How to estimate damage thresholds

The following instructions are a synthesis from the field-derived damage thresholds of Delaplane and Hood (1997, 1999) and Delaplane et al. (2010) for the south-eastern USA, Strange and Sheppard (2001) for the north-western USA, and Currie and Gatien (2006) for Manitoba, Canada. All of these studies used a design in which colonies of uniform strength and mite density are experimentally set up, applications of acaricide made at different times to create a spread of mite history and colony condition, and samples taken regularly to document mite levels and colony condition. With some, negative controls are present as colonies that are never treated, and positive controls present as colonies that are treated continuously. Thus, a range of mite densities exists across the experiment in space and time, and every colony has a history of known mite levels and colony strength at the time it was treated.