Feasibility of surveying pesticide coverage with airborne fluorometer

Response of a Fraunhofer line discriminator (FLD) to varying distributions of granulated corncobs stained with varying concentrations of Rhodamine WT dye was tested on the ground and from an H-19 helicopter. By design the instrument detected fluorescence specifically at the sodium D2 Fraunhofer line (5890 angstroms). The granules are used as a vehicle for airborne emplacement of poison to control fire ants in the eastern and southeastern United States. The granules are dropped with considerable precision but some targets are inevitably missed. It was hoped that the FLD could aid in detecting missed target areas. Test results showed that the granules are detectable by FLD but that the concentration must be too great to be practical with the present FLD. Possible methods for enhancement of response may include: (1) increasing dye concentration; (2) incorporating with the poisoned granules a second material to carry the dye alone; (3) use of a more strongly fluorescent substance (at 5890 A); (4) modifying the time interval after dyeing, or modifying the method of dyeing;(5) modifying the FLD for greater efficiency, increased field of view (FOV), or larger optics; or (6) experimenting with laser-stimulated fluorescence.