DEGRADATION STUDIES OF THE NONLETHAL BIRD REPELLENT, METHYL ANTHRANILATE

Methyl anthranilate (MA), a food grade flavor and fragrance additive, has been reported to be an effective non-lethal bird repellent in a va riety of situations. Despite the experimental success of MA, field stu dies have yielded widely differing levels of efficacy. Diminished effi cacy in some field trials probably results from the failure of specifi c formulations to retain or protect the active ingredient under natura l conditions. Therefore, a clearer understanding of the physical and c hemical factors affecting the stability of MA is needed. We undertook a series of laboratory studies on hydrolysis, photolysis and microbial degradation of MA, the results of which could be useful in the develo pment of appropriate formulation strategies and residue analyses. We f ound the n-octanol:water partition coefficient, (P) to be 84. MA is no t subject to hydrolysis at 25 degrees C in phosphate buffer media at p H 5.0, 7.0 and 9.0. MA slowly photodegrades under simulated UV 'sunlig ht'. Forty-four percent of MA is lost after 432 h illuminance at 1.25 mW cm(-2), which is equivalent to approximately 1200 h natural sunligh t (40 degrees N, noontime, June). Kinetic data indicate that the initi al step of photolysis, subsequent to excitation, is a second-order rea ction with respect to MA. A major photodegradation product appeared in an amount of about 10% of the mass balance and was determined to be a n oxidized trimer of MA. MA is primarily affected by aerobic microbial degradation. For a 12:12 h light:dark, under laboratory illumination, 12% of water-solubilized material can be lost in the first seven days . Losses were 30% and 42% at 16 and 27 days, respectively. Under condi tions of optimal bacterial growth (warmth and darkness) loss of MA was 22% at nine days and 100% by 20 days. The susceptibility of MA to mic robial degradation is promising for the prospects of developing formul ated, environmentally safe, bird repellents.