I was in the 355th Civil Engineering squadron and was the head of operations and maintenance 67-68. The roads and grounds section worked for me. It was a composite of airmen and Thai laborers. Obviously it has been a long time so the memory is certainly not 100% but I do not remember spraying being the principal method of vegetation control. We had a very large Thai labor force and much of the work was done by hand. We did have a major jungle clearing effort of 20 or so acres but it was done total with machines (bull dozers,etc).