Field studies to determine the effects of spinosad on the predatory bugs Anthocoris nemoralis and A. nemorum.

The predatory bugs Anthocoris nemoralis and A. nemorum are important predators of the pear psylla (Psylla pyri) in pear orchards. To effectively control psylla infestations the use of insecticide treatments are often necessary so it is desirable to adopt products and use patterns which protect or conserve natural predator populations. Spinosad (the active ingredient in TRACER* insecticide) is highly active on psylla when applied up to two times after flowering. To investigate the effects of spinosad on A. nemoralis and A. nemorum a series of field trials were conducted between 1998 and 2005 in pear. Findings from these trials showed that spinosad applied at the psylla rate may cause minor short term effects on A. nemoralis and A. nemorum specifically to very young (or recently hatched) nymphs. However, due to the rapid photodegradation of spinosad recovery of predatory bug populations follows a few days after final application. The occasional depressive effect due to spinosad applications was considered to be due mainly to the removal of the pear psylla prey as spinosad has excellent efficacy on this pest. Findings from the trials demonstrated that predatory bug populations recover rapidly within a few days after the second application in order to control any new pear psylla attack. Therefore, spinosad can be considered as a valuable new tool for controlling pear psylla populations in pear orchards and to be compatible with augmented biological control by the predatory bug population.