There are two ways in which pheromone traps have been used in monitoring codling moth:  (1) counting the number of males caught per week (or cumulatively) to assess the potential of a population for causing economic injury; and (2) using the time of first continuous capture of males as a biological reference (or biofix) point for predicting time of egg hatch and therefore optimum timing of pesticide treatment (Whalon & Croft 1984, Brunner et al. 1992, Vickers & Rothschild 1992, Pitcairn et al. 1992).  Although need for pesticide application based on numbers of males captured seems to be a viable approach in some apple growing areas (Vakenti & Madsen 1976), it has not proven reliable in other regions.  The reasons may be several, including differences in distances over which males respond to pheromone compared to distances over which females respond to fruit tree stimuli, abundance of virgin females within and without the orchard confines, and meteorological factors affecting male activity and pheromone release (Riedl & Croft 1974).  Using the biofix point, in conjunction with number of degree days accumulated above 10  C (the threshold for ovary and egg development) since the biofix point, provides a comparatively reliable method for proper timing of pesticide use in orchards that annually require treatment against codling moth.

A summary of sampling and monitoring procedures for apple insect pests is found in Beers et al. (1994).  Basically, three general sampling techniques are used in pome fruit entomology research and decision-making (Fling 1991):  visual sampling, beating tray, and various kinds of traps.

Indirect pests on foliage, twigs, or branches, eggs on fruit, and injury symptoms are adequately sampled by direct visual observations.  The beating tray sampling method is used for pear psylla during the dormant season, and during the growing seasons to survey plant bugs, larval stages of foliage feeding caterpillars and predators and parasitoids of aphids, and other phytophagous species.  Pheromone traps are used to monitor, in addition to the codling moth, the orange tortrix and other tortricid moths and the San Jose scale.  Visual traps (using shape and color) may be combined with plant odor or pheromones to monitor apple maggot flies, and western cherry fruit flies.  Refer also to Table 7, page 39 for a key to the main sampling and monitoring technique most commonly recommended for the major apple and pear insect pests.