Spontaneous N,N'-dibutylurea (DBU) formation in Benlate DF formulation under elevated temperatures

Area of Science:

• Agricultural Chemistry
• Environmental Science
• Plant Pathology

Background:

• Benlate DF is a fungicide formulation containing benomyl.
• Thermal degradation can alter the chemical composition and efficacy of pesticides.
• Understanding pesticide stability under various environmental conditions is crucial for agricultural safety and effectiveness.

Purpose of the Study:

• To investigate the thermal degradation products of benomyl in Benlate DF.
• To determine the role of formulation ingredients in degradation.
• To assess the impact of degradation on fungicide phytotoxicity.

Main Methods:

• Analysis of Benlate DF samples subjected to elevated temperatures (above 55°C and 70°C).
• Identification of degradation products using chemical analysis.
• Lettuce seedling bioassay to evaluate phytotoxicity of heat-treated fungicide.

Main Results:

• Thermal degradation of benomyl in Benlate DF above 55°C produces N,N -dibutylurea (DBU).
• Starch within the formulation acts as an internal water source, facilitating degradation without external moisture.
• Heat-treated Benlate DF with accumulated DBU showed enhanced phytotoxicity in lettuce bioassays.
• DBU accumulation was confirmed in samples stored in a hot shipping container in Hawaii.

Conclusions:

• DBU formation is an inherent property of Benlate DF under thermal stress.
• High temperatures and humidity, common in tropical regions, create optimal conditions for DBU formation.
• The degradation process can lead to increased phytotoxicity, potentially impacting agricultural applications.