SYMPOSIA PAPER Published: 01 January 1996

Photolytic Degradation of Formulated Avermectins: Effect of P-Aminobenzoic Acid (PABA)


A distinctive feature of the foliarly-applied avermectin insecticides is the relative ease with which they decompose under photolytic conditions. From a product perspective it would be an advantage, in certain cases, to extend slightly the “window” of control after application. Consequently, a formulation study was undertaken to characterize the degradation kinetics of two averraectins; emamectin benzoate, and abamectin, in the presence of potential photostabilizers. Interestingly, the use of PABA (p-aminobenzoic acid) in this study did not show the stabilizing effect that was expected from this widely used and effective sunscreen. This report describes the kinetic study involving PABA and discusses possible reasons why some traditional sunscreens may not be the materials of choice for improving the photostability of crop protection products.

Author Information

Peterson, RF
Merck Research Laboratories, Three Bridges, NJ, USA
Alvarez, MD
Merck Research Laboratories, Three Bridges, NJ, USA
Mookerjee, PK
Merck Research Laboratories, Three Bridges, NJ, USA
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Developed by Committee: E35
Pages: 88–96
DOI: 10.1520/STP16033S
ISBN-EB: 978-0-8031-5327-1
ISBN-13: 978-0-8031-2007-5