Field studies were conducted in central Texas to determine the extent of ULV malathion degradation over time and in the presence or absence of sunlight. The purpose of the work was to obtain a better understanding of the factors contributing to ULV malathion degradation, so future steps can be taken to combat the rapid degradation seen with the material. Studies showed that malathion degraded more rapidly in sunlight. There was also significant degradation of the material over time.