These results show that pre-flowering treatments were the most effective and pre-flowering granular applications provided the greatest profit while minimizing the risk to foraging bees.

A great deal of research effort is now directed towards the screening of insecticides for their selectivity so that chemicals which are less toxic to natural enemies can be recommended for use. The physiological selectivity of an insecticide depends on either a decreased sensitivity in the natural enemy at the target site or an enhanced rate of detoxification compared with the pest insect. If the natural enemies have different detoxification pathways from the pest, then this could be exploited by using insecticides that can be detoxified more readily via the pathway used by natural enemies. Insect herbivores and omnivores rely heavily on oxidative detoxification pathways in developing resistance to insecticides (Georghiou and Saito, 1983) whereas entomophagous arthropods appear to use esterase and transferase activity to detoxify insecticides. Thus, the design of insecticides that are primarily detoxified non-oxidatively or activated oxidatively should produce chemicals that are favourably selective for natural enemies (Mullin and Croft, 1985).

There is a great need for research in this subject area to ascertain the biological, physiological and biochemical differences between pests and natural enemies, so that screening for physiological selective insecticides can proceed at a greater pace.

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