I distrust a lot of what is published due to how I witnessed what goes on in industry.
Here is what I found on research with the IGR's ingredient methoprene. Note in the 1991 research the number of animals in the trial. This is typical of much of the information we are "privileged" to receive and interpret.
Concern over methoprene's activity against beneficial organisms (in particular dung beetles) has been debated, especially with studies showing conflicting evidence.
Blume et al. (1974) found that cattle fed methoprene (in a gelatin capsule) at a rate of 1mg/kg produced dung that reduced Onthophagus gazella survival by 1.8% the day after treatment and 32.6% by day five. They also found as little as 5 ppm of methoprene (52.5% EC) mixed directly into dung could cause 33.3% mortality in O. gazella. One-hundred percent (100%) mortality was achieved by mixing 100 ppm of methoprene into dung. Adult beetles emerging from treated dung, however, were normal and produced normal offspring.
Fincher (1991) treated an animal with 3.8 mg/kg of methoprene in bolus form and subjected the dung beetles Onthophagus gazella and Sisyphus rubrus Pachalidis to its dung. He found no significant difference between the percent of adult eclosion in beetles using the control dung and those using the treated dung. Horn flies, however, feeding on the same treated dung experienced a 95.3% reduction in adult emergence even after 15 weeks post-treatment.
